The Impact of the Experimental ‘Grappler Quest’ Training on the Structural Profile of Brazilian Jiu-Jitsu Athletes—A Randomized Controlled Trial

Featured Application

Grappler Quest has a multidimensional impact on the structural profile of BJJ athletes while being a safe and easy-to-use tool in standard training facility conditions.

Abstract

Background: The effectiveness of innovative training interventions has not yet been adequately tested in Brazilian jiu-jitsu (BJJ). This study aimed to evaluate the effectiveness of the Grappler Quest (GQ) training program on the structural profile of BJJ athletes and to examine the relationship between training experience and outcomes. Methods: A randomized controlled trial involving 44 BJJ athletes was conducted to assess the effects of an 8-week training program. The experimental group (EXP; n = 22) followed the GQ program (training stations) while the control group (CON; n = 22) followed a standard training cycle. The structural profile was assessed before and after the intervention, and the relationship between training experience and GQ effects was analyzed. Results: In the EXP group, significant improvements were observed across all structural variables (p < 0.05), with the largest increases in chest mobility (+1.03 cm), thigh circumference (+1.5 cm), and the muscularity of the upper arm (+1.48), lower leg (+1.33), and thigh (+2.60). The greatest reductions occurred in fat tissue (FM% −1.76; FM kg −1.55; sum of three skinfolds −1.21 mm; p < 0.001), with favorable somatotype changes. In the EXP group, training experience significantly correlated with outcomes: positively with fat tissue (r_s = 0.49–0.64) and negatively with muscle mass (r_s = −0.44–0.81). Conclusions: GQ improved the structural profile of BJJ athletes, with its effectiveness showing a stronger correlation with the progress of athletes with shorter training experience. The GQ strategy is recommended as an effective addition to BJJ training.

1. Introduction

The primary goal of sports training is to enable athletes to achieve optimal performance (e.g., in the sport jiu-jitsu) [1]. To maximize training effectiveness, it is essential to develop and refine components such as motor fitness, exercise capacity, and the technical–tactical model, which together form the athlete’s multidimensional morpho-functional profile [2]. In weight-class sports, body composition is a crucial factor [3]. These factors are considered important determinants of sporting success [4]. Based on an athlete’s structural profile, the weight category in which performance is likely to be most favorable can be planned, as can individualized training programs [3]. Somatotype, in turn, provides a three-dimensional assessment of body composition and serves as a key indicator for analyzing morphological changes resulting from regular sports training [5]. Information from these areas forms the basis for developing individualized technical and tactical plans for competition, with the training process aimed at developing specific technical skills that are most compatible with the athlete’s somatic profile [3].

The training process in combat sports continues to evolve, influenced by scientific research reporting, among other things, new assessment tools and innovative training methods. This evolution is particularly evident in well-established and prestigious Olympic disciplines such as Boxing [6], judo [7], Karate (held only once at the XXXII Olympic Games in Tokyo) [8], Olympic Taekwondo [9], and Wrestling [10]. A crucial aspect of this development is the exploration of new training stimuli, which are intended to contribute to the optimization of athletic performance—an idea emphasized in numerous publications [11,12,13,14,15]. Such efforts uncover a wealth of information with significant scientific and cognitive value while also supporting effective implementation in practical training settings.

Among the relatively young combat sports disciplines is Brazilian jiu-jitsu (BJJ) [16], which is gaining increasing popularity worldwide. It is a form of combat based on techniques aimed at subduing the opponent (joint locks, chokes, holds) and ground fighting (scored guard passes, sweeps, and technical positions such as knee-on-belly, mount, and back control) [17]. The existing literature suggests that training and competition preparation prioritize comprehensive motor fitness, the development of specific capacities, and a wide range of technical–tactical skills combined with high physical conditioning to meet the demands of training and competition [18,19]. BJJ movement patterns vary in intensity—high, moderate, and low—highlighting the need for interval-based adaptations [20]. Athletes require high levels of absolute strength and explosive power to gain a decisive advantage over opponents [21]. Additionally, above-average muscular endurance—particularly grip endurance—is necessary to control the opponent throughout the duration of a match [19,22]. According to Castarlenas and Solé, a high level of aerobic power helps delay fatigue and accelerates recovery between matches in the tournament-based BJJ format [23]. Flexibility is also an essential trait, distinguishing elite from non-elite athletes [24].

Because BJJ is organized into weight categories, athletes must maintain low body fat while developing higher muscle mass [20]. Body fat has been observed to increase gradually with progression to higher weight classes [25]. Marinho et al. reported that elite-level BJJ athletes have lower body fat percentages than their non-elite counterparts [24]. The mesomorphic profile is predominant, which is associated with competitive success [26,27], as well as with the strategic model of sport combat (a higher mesomorphic component favors early fight finishes while a higher level of ectomorphy is associated with victories by points within the regulated time limit) [28]. Importantly, it is believed that success in BJJ is largely determined by the athletes’ anthropometric characteristics [20]. According to coaches, an appropriate structural profile supports the development of specific BJJ technical skills and the desired motor abilities.

This raises the following question: how can the structural profile of a BJJ athlete be effectively influenced and improved? An analysis of scientific reports reveals a knowledge gap in this area. Moreover, thematic scientific reviews highlight the need for the further exploration of this domain [20]. In the search for innovative training stimuli, it is worth considering the design of a training program based on the principles of functional training, incorporating small, thematically organized resistance training circuits [29,30]. This format can effectively optimize athletes’ body compositions while simultaneously improving their functional profiles [30]. Moreover, appropriately applied hybrid training models may lead to better outcomes compared to conventional training [12], which often separates technical preparation from physical conditioning. Our experimental training protocol is based on these principles, offering a comprehensive and specific training stimulus that reflects the modern demands of BJJ. It integrates a variety of exercise components (resistance, gymnastic, technical, and coordination drills), simulating the intermittent and multidimensional nature of BJJ combat. Such an approach is intended to optimize the structural profile of BJJ athletes, whose competitive activity is determined by weight categories. Additionally, this knowledge may hold significant scientific and practical value, particularly for coaches and athletes in this discipline, ultimately contributing to the continued development of the sport.

Considering the above premises, the primary aim of this study was, first, to evaluate the effectiveness of the experimental training program Grappler Quest (GQ—based on the principles of small, thematically focused exercise circuits) on the structural profile of a population of Brazilian jiu-jitsu (BJJ) athletes. The second aim was to identify the relationship between the duration of training experience and the training effects achieved through the experimental intervention.

Based on existing scientific reports and our coaching and athletic experience, we hypothesized that participation in the GQ program would lead to significant changes in selected indicators of the structural profile of BJJ athletes. Specifically, we expected an increase in the girths of major muscle groups (chest, arm, thigh), an improvement in limb muscle mass indices and the mesomorphic component of the somatotype, and a decrease in fat-related variables such as skinfold thickness and the endomorphic component.

2. Materials and Methods

The study was approved by the Ethics Committee of the District Medical Chamber in Krakow (No. 226/KBL/OIL/2023). In accordance with the Helsinki Declaration requirements, the participants were informed about the research objectives, methods, potential side effects, and the option to withdraw from the study at any time without providing a reason. The participants provided written consent to participate.

2.1. Study Design

We employed a randomized controlled trial with repeated measures. The testing procedure was conducted both before and after an 8-week intervention period. In the experimental group (EXP), the intervention was integrated into their regular training routine, with the addition of thematically structured exercise circuits. The control group (CON) followed their standard Brazilian jiu-jitsu (BJJ) training program. The experimental stimulus was applied in order to reliably compare the training effects obtained under the GQ conditions with the outcomes of traditional training methods commonly used in sports clubs.

2.2. Participant Characteristics

A total of 44 competitive male BJJ athletes from Poland were included in the study using purposive sampling. The a priori sample size was estimated in G*Power v.3.1.9.6 for a repeated-measures ANOVA, assuming a large effect size (f = 0.65), α = 0.05, and target power of 0.80. The effect size was adopted based on the assumption of a large intervention effect. Given the limited literature specifically related to BJJ, we chose to apply a conservative estimate of a large effect size. This yielded a required minimum of 40 participants (20 per group). We enrolled 44 athletes (22 per group), which met the a priori target for the ANOVA design. Initially, 48 competitive athletes were recruited. Four were excluded from the study due to exclusion criteria (history of injuries or health issues). Inclusion criteria were as follows: a minimum of 4 years of training experience, current medical clearance, no history of serious injuries, a positive medical recommendation, no use of supplements (during the study period) or doping, and active participation in competitions. Exclusion criteria included the opposite of the above aspects, as well as current injuries or conditions that could interfere with training or study participation, lack of consent to participate in the study, and no prior experience in sports competitions. These criteria were established due to the high intensity of the proposed training format, which required participants to have a musculoskeletal system capable of withstanding such physical effort. The average body mass of participants was 78.33 ± 10.89 kg, and average height was 177.12 ± 6.20 cm, with a BMI of 24.92 ± 2.85. Participant age ranged from 21 to 31 years (mean age: 25.81 ± 3.22). Training experience ranged from 4 to 13 years of systematic training, with 4 to 6 sessions per week depending on the mesocycle (mean training experience: 7.57 ± 2.70 years). Participants’ belt ranks ranged from blue to black belt (n = 4 black belts; n = 10 brown belts; n = 14 purple belts; n = 16 blue belts). The study was conducted during the preparatory phase. Athletes were not following any restrictive diets. All participants competed at the master class level—international, national, or local—and some had achieved significant sporting success, including medals at the European and Polish Championships and other prestigious grappling tournaments. Information on chronological age, training experience, competitive activity, and competitive tenure was obtained through a diagnostic survey conducted via direct interviews with athletes and their coaching staff. Selection of research groups (procedure) was as follows: the sample included at least four representatives from each of seven senior weight categories (n = 4 up to 64 kg; n = 4 up to 70 kg; n = 12 up to 76 kg; n = 12 up to 82.3 kg; n = 4 up to 88.3 kg; n = 4 up to 94.3 kg; n = 4 up to 100.5 kg), according to the regulations of the International Brazilian Jiu-Jitsu Federation (IBJJF) [16]. Based on purposeful subgroups formed according to weight category, the total sample was divided into two groups. At this stage, group assignment was randomized—one participant from each weight category was randomly allocated to one of the two research groups: EXP (n = 22) and CON (n = 22). Each participant was assigned a unique identification number, and group placement was determined using a random number generator. Allocation concealment was ensured through the use of sealed, opaque, and sequentially numbered envelopes prepared by an independent researcher who was not involved in participant enrollment. This procedure minimized the risk of selection bias and aligned with best practices for randomized controlled trials. Due to the nature of the intervention, blinding was not feasible. Both participants and trainers were aware of group allocation, and outcome assessments were conducted without blinding. This three-stage selection process (stages 1 and 2: purposive; stage 3: random) allowed for the formation of groups with similar ages, training experience, and structural profiles, without significant between-group variation (

Table 1. Statistical characteristics of basic somatic features, age, and training experience in the studied groups of athletes (EXP vs. CON).

Variables	Group EXP (N = $22); \tilde{\mathit{x}}$ ± sd	Group CON (N = $22); \tilde{\mathit{x}}$ ± sd	p-Value
Age [years]	26.02 ± 3.24	25.59 ± 3.25	0.597
Body height [cm]	177.34 ± 6.33	176.90 ± 6.22	0.819
Body weight [kg]	78.79 ± 12.05	77.88 ± 9.86	0.879
BMI [kg/m2]	24.98 ± 3.04	24.86 ± 2.71	0.894
Training experience [years]	7.50 ± 2.67	7.64 ± 2.79	0.879

$\tilde{x}$—arithmetic mean; sd—standard deviation; p—level of significance.

, Appendix A—

Table A1. Statistical characteristics of the structural profile and their intergroup variation in the studied groups (EXP vs. CON) of BJJ athletes (n = 44), baseline assessment (pre-test).

Variables	Group EXP (N = 22)				Group CON (N = 22)				p-Value
Anthropometric Characteristics
	$\tilde{\mathit{x}}$ ± sd	V%	Min	Max	$\tilde{\mathit{x}}$ ± sd	V%	Min	Max	p
Body height [cm]	177.34 ± 6.33	3.57	168.00	190.70	176.90 ± 6.22	3.52	168.72	191.30	>0.05
Arm length [cm]	34.15 ± 2.23	6.52	29.50	37.00	34.13 ± 2.20	6.44	29.50	37.20	>0.05
Forearm length [cm]	26.69 ± 1.46	5.45	24.30	29.50	26.81 ± 1.34	4.99	25.00	29.70	>0.05
Thigh length [cm]	57.33 ± 3.63	6.33	53.00	62.00	57.37 ± 3.81	6.65	52.80	63.20	>0.05
Lower limb length [cm]	38.11 ± 3.60	9.45	31.60	43.00	37.90 ± 3.57	9.41	31.30	43.00	>0.05
Elbow width [cm]	7.16 ± 0.11	1.59	6.98	7.36	7.14 ± 0.09	1.20	6.99	7.31	>0.05
Knee width [cm]	10.08 ± 0.18	1.83	9.84	10.41	10.06 ± 0.17	1.65	9.78	10.38	>0.05

$\tilde{x}$—arithmetic mean; sd—standard deviation; min—minimum value; max—maximum value; V%—coefficient of variation; p—level of significance.

and

Table A2. Statistical characteristics of the structural profile and their intergroup variation in the studied groups (EXP n = 22 vs. CON n = 22) of BJJ athletes (n = 44).

Measurement	Group EXP (n = 22)					Group CON (n = 22)					F	p	η2
	$\tilde{\mathit{x}}$ ± sd	Me	Min	Max	V (%)	$\tilde{\mathit{x}}$ ± sd	Me	Min	Max	V (%)
Body weight [kg]
I pre-test	78.8 ± 12.1	77.3	60.1	100.4	15.3	77.9 ± 9.9	77.8	60.9	97.9	12.7	0.08	0.786	0.001
II post-test	78.0 ± 11.9	76.3	60.0	99.8	15.2	77.7 ± 9.7	77.5	60.5	97.5	12.5	0.01	0.923	<0.001
Arm circumference at rest [cm]
I pre-test	31.0 ± 3.3	30.6	24.3	37.5	10.6	30.9 ± 3.3	30.5	24.2	37.4	10.6	0.01	0.905	<0.001
II post-test	31.5 ± 3.5	31.7	24.2	38.0	11.0	31.1 ± 3.2	30.7	24.6	38.0	10.4	0.19	0.665	0.004
Arm circumference under tension [cm]
I pre-test	34.3 ± 3.4	33.6	27.0	40.2	9.9	34.1 ± 3.5	33.5	26.3	40.1	10.1	0.02	0.878	<0.001
II post-test	35.2 ± 3.8	35.5	26.8	40.9	10.7	34.4 ± 3.4	33.8	26.5	40.3	9.9	0.52	0.477	0.01
Maximum forearm circumference [cm]
I pre-test	28.1 ± 2.7	27.4	24.0	33.9	9.6	28.2 ± 2.7	27.5	24.0	34.0	9.4	0.04	0.853	<0.001
II post-test	28.3 ± 2.8	27.7	23.7	34.3	9.8	28.3 ± 2.6	27.6	24.3	33.9	9.2	0.002	0.964	<0.001
Minimum forearm circumference [cm]
I pre-test	18.5 ± 1.6	18.3	15.5	20.9	8.6	18.5 ± 1.5	18.5	15.6	20.9	8.3	0.01	0.908	<0.001
II post-test	18.6 ± 1.7	18.5	15.5	21.1	9.0	18.6 ± 1.6	18.5	15.9	21.0	8.5	<0.001	0.985	<0.001
Chest circumference at rest [cm]
I pre-test	92.1 ± 8.9	89.1	76.0	109.2	9.7	93.3 ± 9.5	90.7	76.3	110.4	10.1	0.19	0.662	0.005
II post-test	92.8 ± 9.2	90.4	75.8	109.8	9.9	93.4 ± 9.3	91.0	76.8	110.7	10.0	0.05	0.818	0.001
Chest circumference on inhalation [cm]
I pre-test	95.6 ± 8.0	94.1	80.0	111.0	8.4	96.0 ± 9.3	93.3	79.2	113.0	9.7	0.02	0.894	<0.001
II post-test	96.5 ± 8.1	95.5	80.0	111.5	8.4	96.1 ± 9.3	93.4	79.1	113.4	9.6	0.02	0.885	<0.001
Chest circumference on exhalation [cm]
I pre-test	90.1 ± 9.1	87.1	75.5	108.0	10.1	89.9 ± 9.2	86.3	74.8	107.4	10.2	0.008	0.931	<0.001
II post-test	89.9 ± 9.1	86.7	75.2	107.7	10.1	90.0 ± 9.2	86.2	75.0	108.0	10.3	0.001	0.971	<0.001
Chest mobility [cm]
I pre-test	5.6 ± 1.9	5.5	2.9	8.6	33.5	6.1 ± 1.4	5.9	4.1	9.6	23.4	1.39	0.245	0.03
II post-test	6.6 ± 1.9	7.0	3.2	9.6	29.4	6.1 ± 1.5	6.0	4.1	10.0	23.9	0.87	0.355	0.02
Waist circumference [cm]
I pre-test	85.4 ± 8.0	85.1	67.5	98.1	9.4	85.3 ± 8.0	84.9	67.4	98.0	9.4	0.003	0.960	<0.001
II post-test	84.7 ± 7.6	84.1	68.00	96.8	8.9	84.7 ± 7.6	84.1	67.5	96.8	8.9	<0.001	0.997	<0.001
Hip circumference [cm]
I pre-test	98.5 ± 7.1	99.4	87.0	112.0	7.2	98.2 ± 7.2	99.0	86.9	112.0	7.3	0.02	0.898	<0.001
II post-test	98.8 ± 7.1	100.0	86.5	112.0	7.2	98.0 ± 6.6	99.0	86.7	110.0	6.8	0.14	0.706	0.003
Maximum thigh circumference [cm]
I pre-test	56.6 ± 4.1	56.9	48.0	62.8	7.2	56.4 ± 4.1	56.8	47.9	62.7	7.2	0.009	0.923	<0.001
II post-test	58.0 ± 4.4	59.2	48.0	64.0	7.6	56.5 ± 4.0	57.2	47.9	62.5	7.1	1.43	0.239	0.03
Maximum lower limb circumference [cm]
I pre-test	37.7 ± 3.2	37.9	31.5	42.4	8.4	37.4 ± 3.1	37.5	31.4	42.0	8.3	0.07	0.795	0.002
II post-test	38.2 ± 3.4	38.5	31.2	42.8	8.8	37.5 ± 3.0	37.5	31.5	42.4	8.0	0.53	0.471	0.01
Minimum lower limb circumference [cm]
I pre-test	23.1 ± 2.1	23.4	19.0	27.2	8.9	23.0 ± 2.0	23.4	18.9	27.0	8.8	0.04	0.848	<0.001
II post-test	23.3 ± 2.2	23.7	19.0	27.5	9.5	22.9 ± 2.0	23.2	19.0	26.8	8.5	0.4	0.581	0.007
Subscapular skinfold thickness [mm]
I pre-test	11.0 ± 3.0	10.6	7.00	16.2	27.2	10.8 ± 2.4	10.4	6.8	16.1	27.1	0.02	0.891	<0.001
II post-test	10.6 ± 2.6	10.1	7.2	15.8	24.9	10.5 ± 2.7	9.5	6.9	15.0	25.4	0.007	0.932	<0.001
Triceps skinfold thickness [mm]
I pre-test	7.7 ± 1.2	7.5	6.0	10.2	15.5	7.6 ± 1.2	7.4	5.9	10.0	15.6	0.08	0.773	0.002
II post-test	7.4 ± 1.1	7.6	5.7	9.6	14.5	7.5 ± 1.2	7.3	5.7	9.8	16.0	0.12	0.733	0.003
Biceps skinfold thickness [mm]
I pre-test	4.5 ± 0.8	4.4	3.2	5.4	16.9	4.4 ± 0.8	4.3	3.1	5.4	17.4	0.09	0.767	0.002
II post-test	4.3 ± 0.6	4.2	3.2	5.1	13.1	4.3 ± 0.7	4.3	3.0	5.5	17.1	0.05	0.820	0.001
Suprailiac skinfold thickness [mm]
I pre-test	10.7 ± 2.9	9.6	7.0	16.3	26.8	10.5 ± 2.9	9.5	5.9	15.8	27.2	0.05	0.822	0.001
II post-test	10.2 ± 2.5	9.3	7.2	15.5	24.2	10.4 ± 2.6	9.5	6.3	15.8	25.5	0.05	0.824	0.001
Abdominal skinfold thickness [mm]
I pre-test	12.5 ± 5.1	12.4	6.00	20.3	40.5	12.2 ± 4.8	12.2	6.1	19.5	39.4	0.05	0.829	<0.001
II post-test	11.3 ± 4.0	11.0	6.00	18.3	35.6	11.2 ± 4.1	10.8	6.2	18.8	36.4	0.005	0.944	<0.001
Calf skinfold thickness [mm]
I pre-test	6.4 ± 1.9	7.0	3.2	9.0	30.2	6.1 ± 1.8	6.7	3.1	8.5	30.0	0.30	0.589	0.006
II post-test	6.3 ± 1.8	6.9	3.2	8.7	28.4	6.1 ± 1.8	6.7	3.1	8.5	29.3	0.10	0.757	0.002
Sum of skinfolds [mm]
I pre-test	29.4 ± 5.6	30.8	20.0	40.9	19.0	28.9 ± 5.5	30.4	19.8	39.8	19.0	0.06	0.802	0.002
II post-test	28.2 ± 4.6	29.5	20.2	38.1	16.3	28.4 ± 5.1	29.1	19.9	38.7	17.8	0.02	0.879	<0.001
BMI [kg/m2]
I pre-test	25.0 ± 3.0	24.3	20.5	31.5	12.2	24.9 ± 2.7	24.5	20.5	30.3	10.9	0.02	0.894	<0.001
II post-test	24.7 ± 3.0	24.0	20.7	31.3	12.1	24.8 ± 2.7	24.4	20.4	30.2	10.8	0.007	0.935	<0.001
Slenderness index [dq]
I pre-test	41.5 ± 1.6	41.9	38.4	43.7	3.8	41.5 ± 1.6	41.7	38.8	44.3	3.8	<0.001	0.982	<0.001
II post-test	41.7 ± 1.6	42.0	38.5	43.7	3.8	41.6 ± 1.6	41.7	38.9	44.3	3.7	0.04	0.846	<0.001
Arm muscularity [dq]
I pre-test	90.7 ± 6.8	88.6	82.4	101.6	7.5	90.4 ± 7.1	88.1	81.2	103.0	7.8	0.02	0.893	<0.001
II post-test	92.2 ± 7.2	90.1	82.0	103.9	7.8	91.0 ± 7.1	88.7	82.0	104.7	7.8	0.30	0.586	0.007
Forearm muscularity [dq]
I pre-test	105.2 ± 6.4	103.8	92.3	114.9	6.1	105.2 ± 5.9	104.5	92.3	115.3	5.6	<0.001	0.978	<0.001
II post-test	105.9 ± 6.9	105.6	91.2	116.3	6.5	105.5 ± 5.6	104.4	93.5	114.9	5.3	0.037	0.849	<0.001
Thigh muscularity [dq]
I pre-test	98.7 ± 4.9	100.1	89.9	106.4	5.0	98.4 ± 5.1	100.0	89.9	106.4	5.2	0.03	0.871	<0.001
II post-test	101.3 ± 5.6	103.0	89.9	112.1	5.6	98.6 ± 5.2	100.2	89.7	107.7	5.3	2.67	0.110	0.06
Lower limb muscularity [dq]
I pre-test	99.7 ± 12.2	95.8	84.0	120.9	12.2	99.5 ± 11.9	96.9	84.0	121.4	11.9	0.001	0.974	<0.001
II post-test	101.0 ± 12.6	98.4	84.3	123.4	12.5	99.7 ± 11.4	97.4	84.1	120.1	11.5	0.14	0.715	0.003
FM %
I pre-test	20.8 ± 3.3	20.4	15.1	26.0	15.7	20.9 ± 2.2	21.1	16.7	25.3	10.4	0.007	0.935	<0.001
II post-test	19.1 ± 4.2	19.2	11.5	25.5	21.9	20.6 ± 2.1	20.4	16.7	25.1	10.3	2.37	0.131	0.05
FM [kg]
I pre-test	16.5 ± 4.0	16.1	10.0	25.0	24.5	16.2 ± 2.4	15.7	12.1	23.1	14.7	0.07	0.795	0.002
II post-test	14.9 ± 4.2	15.1	7.5	23.4	28.0	16.0 ± 2.4	15.5	12.9	22.9	14.8	1.01	0.321	0.02
LBM [kg]
I pre-test	62.3 ± 9.3	61.7	45.1	81.3	14.9	61.7 ± 8.4	61.6	45.9	81.5	13.6	0.06	0.809	0.001
II post-test	63.1 ± 9.6	62.8	44.7	82.2	15.1	61.7 ± 8.2	62.0	46.3	81.2	13.3	0.25	0.618	0.006
Endomorphy [dq]
I pre-test	2.9 ± 0.6	3.0	1.9	4.0	21.0	2.8 ± 0.6	2.9	1.9	4.0	21.0	0.05	0.820	0.001
II post-test	2.7 ± 0.5	2.8	1.9	3.8	18.3	2.8 ± 0.5	2.8	1.9	3.8	19.8	0.003	0.954	<0.001
Mesomorphy [dq]
I pre-test	6.4 ± 1.1	6.5	4.6	8.2	17.1	6.4 ± 1.1	6.5	4.3	8.1	17.4	0.00	1.00	0.00
II post-test	6.7 ± 1.2	6.8	4.6	8.4	18.0	6.5 ± 1.1	6.6	4.4	8.2	16.5	0.39	0.535	0.009
Ectomorphy [dq]
I pre-test	1.6 ± 0.7	1.8	0.2	2.6	46.2	1.6 ± 0.7	1.7	0.3	2.9	45.3	<0.001	0.984	<0.001
II post-test	1.7 ± 0.7	1.8	0.2	2.6	44.3	1.6 ± 0.7	1.7	0.4	2.9	44.7	0.03	0.870	<0.001

$\tilde{x}$—arithmetic mean; Me—median; sd—standard deviation; Min—minimum value; Max—maximum value; V%—coefficient of variation; dq—dimensionless quantity; I—first measurement period (pre-test); II—second measurement period (post-test); F—statistic from the ANOVA test; p—level of significance for differentiation; η²—Eta-squared, measure of effect size.

).

The research was conducted at the Legion Team Tarnów Sports Club and the Grappling Kraków Sports Club.

2.3. Characteristics of the Experimental Intervention

The intervention involved manipulating the training process of the athletes in the EXP group by modifying their training program in accordance with the principles of pedagogical experiments [31,32]. Specifically, the EXP group followed an experimental 8-week training program incorporating thematically structured exercise circuits (3 experimental training sessions per week + 1 sparring session) while the CON group followed a standard BJJ training program based on a general training cycle (3 sessions per week + 1 sparring session). Training interventions in both groups were conducted by experienced, certified trainers who had been trained by the authors of the project. Additionally, participants received guidance on recommended meals to maintain a balanced diet, adequate rest, and consistent training intensity (including adherence to coaching staff recommendations, diligence, and attendance). To assess the profile of changes induced by the training stimulus, two measurement points were established. The first took place before the start of the mesocycle (baseline assessment of variables—pre-test). The second set of measurements was conducted after the completion of the 8-week training period (assessment of effectiveness—post-test). The effects of the experimental training were evaluated both within the EXP group (intragroup analysis) and in comparison to the CON group (intergroup analysis), which served as the reference point. In the final analysis, only participants with a minimum attendance of 90% were included (n = 44). A flowchart of the research intervention is presented in Figure 1.

2.4. Characteristics of the Applied Experimental Training Program to the EXP Group

The proposed experimental training program was developed based on various approaches to functional training guidelines [29] and structured in the form of small, thematically focused exercise circuits [30]. A key priority of the program was exercise diversity and the use of a wide range of training equipment. The exercises were designed and implemented with the aim of targeting all muscle groups of the participants, both analytically and holistically.

Table 2. Experimental training program—methodological framework.

Experimental Training Program Based on the Circuit Method
Parameter	Value/Description
Number of exercise circuits	3
Number of exercises per circuit	5
Repetitions/Duration per exercise	Circuit I: 8 to 15 reps/Circuit II and III: 30 s
% of maximum load	Up to 50% of body mass
Exercise tempo	Circuit I: 2-1-2-1/Circuit II and III: fast-paced
Rest time between circuits	180 s

presents the methodological framework of the experimental training program.

The training intervention featured a modification involving the implementation of various forms of resistance training, organized into thematically structured exercise blocks:

• Strength-endurance circuit: Utilizing bodyweight resistance and external loads (e.g., medicine balls, weight plates, dumbbells).
• Functional circuit: Incorporating BJJ-specific drills, performed individually or using equipment and training aids. BJJ drills involve repeating discipline-specific movements multiple times to develop muscle memory. Through consistent repetition aimed at perfecting technique, athletes refine their BJJ movement patterns. The intended outcome is that, upon noticing an opponent’s error, athletes execute attacks or defenses as naturally as walking is for the average person [33].
• Specialized circuit: Exercises targeting motor abilities that are most frequently engaged in the specific movement patterns characteristic of BJJ.

Each training session’s main segment was divided into the three described circuits (see

Table 3. Types of exercises used in the experimental program.

I Strength-Endurance Circuit	II Functional Circuit	III Specialized Circuit
Pull-ups on a suspended gi to full elbow flexion and extension	Wall roll 1	BJJ Burpees 5 across the length of the training hall
Classic squat combined with a medicine ball throw over the head and then catching it	Knee-on-belly 2 with side-to-side switching (R-L) on a training bag	Sit-up from the back position into a kimura setup 6
Trunk twists with a plate held in hands, elbows bent at chest height	Minimum forward and backward rolls on a gymnastic ball (or other exercises that are not a technical barrier, e.g., handstands, clean and press, rolls, etc.)	Isometric hold of steel maces at a 90-degree elbow angle
Deadlift with kettlebells, pulling the weight up to the clavicle line (hands close to the torso)	BJJ floor climb 3 forward and backward across the training hall	Stable standing on a gymnastic ball with feet or knees, no hands used for support
Deep push-ups on parallel bars	Gymnastic exercise set 4 across the training hall with fluid motion	Jump over a rope (1 m height) followed by crawling under it

¹ Wall roll—A specialized BJJ exercise with a specific movement pattern (natural gymnastics) [33]. ² Knee-on-belly—A ground position scored in BJJ [33]. ³ BJJ floor climb—A specialized BJJ exercise with a specific movement pattern (natural gymnastics) [33]. ⁴ Gymnastic exercise set—Composed of the following elements: T1. Forward roll—T2. Headstand with muscle power and self-support by forward roll—T3. Handstand with self-support by forward roll—T4. Direction change with a jump and a half-turn (180 degrees)—T5. Backward roll. ⁵ BJJ Burpees—An intense exercise engaging all muscle groups. One sequence consists of 4 movements performed one after the other: T1. Forward torso bend with hands on the floor—T2. Hand transition to a front support position—T3. Arm bend in front support—T4. Jumping transition to a supported squat—T5. Jumping upwards [33]. ⁶ Kimura—from a supine position, transition to a seated position with torso rotation to simulate the kimura lock (solo drill) or execute the shoulder lock technique (with a partner) [33].

). In the first circuit, each of the five exercises was performed for 8 to 15 repetitions (in line with the principles of individualization and progressive difficulty) within a 60 s timeframe (tempo: 2-1-2-1, meaning 6 s under tension per repetition and approximately 60 s per set for 10 reps, for example). In the two remaining circuits, the exercises were performed for time, with 30 s allocated per exercise. A detailed demonstration of the exercises performed in the themed station-based circuits is provided in the Supplementary Materials in the form of an instructional and training video.

Training sessions were conducted three times per week in the evenings (19:00–20:30), each lasting 90 min. Every training session began with a 10 min warm-up (exercises preparing the body for physical exertion) and concluded with 15 min of specialized stretching exercises targeting body areas where a large range of motion was most desired in the discipline—specifically the most heavily utilized regions in BJJ: the thoracolumbar spine, hamstring complex, posterior knee tendons, and hip joint structures. In addition, a fourth weekly training session was dedicated to sparring practice. The total weekly training time amounted to 360 min, of which 240 min was devoted to the experimental intervention.

2.5. Characteristics of the Standard Training Program for the CON Group

Before the experiment, the BJJ athlete population (n = 44) participated in standard BJJ training routines (technical knowledge acquired through seminars, media, and literature). A typical training session consisted of the following. Warm-up (introductory part): Exercises preparing the body for physical effort, including energizing games and general developmental exercises. Main part: Exercises aimed at developing and refining BJJ-specific fitness; instructional or improvement-focused technical drills; and sparring—either full-form or task-based, emphasizing isolated technical–tactical elements. Cool-down (final part): Exercises incorporating mobility, flexibility, and postural correction components. If resistance training was included, it primarily consisted of bodyweight exercises.

This training format was applied three times per week for the CON group. A shared element for both groups was one weekly sparring session.

2.6. Anthropometric Measurements

All measurements were performed in accordance with standard anthropometric procedures [34], based on the identification of anthropometric landmarks. Body height (B-v) and bone lengths (forearm r-sty, upper arm a-r, thigh sy-ti, lower leg ti-sph) were measured using an anthropometer from GPM Anthropological Instruments (Siber Hegner Machinery Ltd., Zurich, Switzerland; accuracy: 0.1 cm). Body mass was measured using a certified electronic scale, TANITA TBF-538 (Tokyo, Japan; accuracy: 0.1 kg). A caliper (GPM, Bachenbülach, Switzerland) was used to measure the widths of the distal ends of the humerus (elbow width cl-cm) and femur (knee width epl-epm). A flexible anthropometric tape (accuracy: 0.1 cm) was used to measure the circumferences of the arm (both relaxed and flexed), forearm (maximum and minimum), chest (at the level of the xiphoid xi process during rest, maximum inhalation, and exhalation), waist (at the level of the waist indentation), hips (across the greatest gluteal prominence), upper thigh, and lower leg (at maximum and minimum girth). To assess subcutaneous fat, a skinfold caliper (constant pressure: 10 g/mm², accuracy: 0.2 mm) was used to measure skinfold thickness at the following sites: subscapular, triceps, biceps, suprailiac, abdominal, and calf. The Ulijaszek and Kerr protocol [35] was followed, and technical error of measurement (TEM) was calculated for reliability, ranging from 0.4 mm to 1.0 mm across different skinfolds. Additionally, the sum of skinfolds was calculated for the triceps, subscapular, and suprailiac sites. The measurements were taken by a researcher with many years of experience.

Based on these measurements, anthropometric indices were calculated [36]: height-to-weight index (BMI): BMI = BW [kg]/BH [m²]; slenderness index: BH [cm]/√(3 × BW [kg]; muscularity indices: calculated for the forearm, upper arm, thigh, and lower leg as Circumference [cm]/Length [cm] × 100; and chest mobility: calculated as the difference between maximal inhalation and exhalation chest circumference.

Body composition components were assessed as follows. Body density (D) was calculated using Piechaczek’s equation [37]:

D = 1.125180 − 0.000176 log X₂ − 0.000185 log X₅

where D—body density (g/cm³), X₂—triceps skinfold (mm), and X₅—abdominal skinfold (mm).

Fat mass percentage (FM%) was calculated using the Keys and Brożek equation [38]:

$$\mathrm{F}\mathrm{M}\%=100({\displaystyle \frac{4.201}{\mathrm{D}}}-3.813)$$

where FM%—fat mass percentage; D—body density (g/cm³).

Fat mass in kilograms (FM kg) [38]:

$$\mathrm{F}\mathrm{M}={\displaystyle \frac{\mathrm{B}\mathrm{M}\left[\mathrm{k}\mathrm{g}\right]\times \mathrm{F}\mathrm{M}\%}{100}}$$

where FM kg—fat mass in kilograms; BM—body mass (kg); FM%—fat mass percentage.

Lean body mass (LBM kg) was calculated as the difference between body mass and fat mass.

Somatotype assessment was conducted using the Heath–Carter method [5]. Based on the anthropometric data and with the use of the Somatotype—Calculation and Analysis software by Sweat Technologies©, (Mitchell Park, South Australia, version 2.0) three body composition components were calculated: endomorphy (fatness), mesomorphy (muscularity and skeletal robustness), and ectomorphy (linearity/slenderness). Each tissue component is expressed on an open-ended scale: 0.5–2.5 indicates a low level of development, 3.0–5.0 a moderate level, 5.5–7.0 a high level, and above 7.5 a very high level [5,39].

2.7. Statistical Analysis

The statistical analysis was performed using PQStat v.1.8.6 and Statistica v.13.3 (Statsoft, Krakow, Poland). Basic descriptive statistics were calculated (arithmetic means, standard deviations, minimum and maximum values, coefficients of variation). The assumption of normal distribution was verified with the Shapiro–Wilk test and the homogeneity of variances with Levene’s test. In cases where these assumptions were not met, logarithmic transformation of the data was applied. To assess within-group changes (before vs. after the intervention), one-way repeated-measures analysis of variance (ANOVA) was used. Comparisons between the experimental and control groups at individual time points were performed using one-way ANOVA for independent variables. Additionally, differences (delta: post-pre) were calculated and compared between groups using one-way ANOVA for independent variables. Alongside p-values, the effect size (η²) was reported and interpreted according to the following classification: small effect η² = 0.01–0.05, medium effect η² = 0.06–0.13, and large effect η² ≥ 0.14. The relationships between selected variables were examined using Spearman’s rank correlation (r_s). The thresholds for interpreting correlation coefficients were as follows: r = 0.0–0.19 very weak, r = 0.20–0.29 weak, r = 0.30–0.49 moderate, r = 0.50–0.79 strong, and r ≥ 0.80 very strong. The degree of intragroup variability was assessed by interpreting the coefficient of variation values: CV < 25% indicates low variability; 25–45% moderate variability; 45–100% high variability; and >100% very high variability [40]. Statistical significance was set at p < 0.05.

3. Results

Regarding the baseline (pre-test) intergroup comparison, the formed research groups (EXP vs. CON) exhibited similar structural profiles, including anthropometric features and indices, skinfolds, tissue components, and somatotypes (Appendix A—Table A1 and Table A2). The CON group showed a qualitative advantage in most of the global variables (out of thirty-three variables, seventeen were more favorable, eleven were less favorable, and five were equal). The variation in all measured variables was not statistically significant (p > 0.05).

After 8 weeks (post-test), the intergroup comparison again showed no significant differences in the structural profile. The EXP group had a qualitative advantage (out of thirty-three variables, twenty-four were more favorable, five were less favorable, and four were equal) in most variables, in contrast to the pre-test (Appendix A—Table A2). However, the observed variation did not show statistical significance (p > 0.05).

The coefficients of variation indicated that internal variability was very low (CV < 25%) for most variables in both groups at pre-test and post-test. Exceptions were observed for the skinfolds under the scapula, above the iliac crest (EXP in pre-test; CON in both terms), on the abdomen, on the lower leg, and in the ectomorphy component (EXP and CON in both terms), where moderate internal variability was observed in most cases (CV = 25.4–46.2). Additionally, regarding chest mobility (both measurement times) and FM kg (post-test) in the EXP group, similar trends were noted. The average values from the two measurement sessions, expressed as CV%, showed that the intragroup variation in the measurements was very low in the EXP group, demonstrating a slight improvement in homogeneity in the post-test during the experimental procedure (average test index CV% pre-test = 15.73; post-test = 15.35) (Appendix A—Table A2).

Table 4. Statistical characteristics of training effects (increments and reductions) in the components of the structural profile and their intergroup variability in the studied groups (EXP n = 22 vs. CON n = 22) of BJJ athletes (n = 44).

Variables	Group EXP (n = 22)			Group CON (n = 22)			d	F	p	η2
	$\tilde{\mathit{x}}$	sd	CV (%)	$\tilde{\mathit{x}}$	sd	CV (%)
Body weight [kg]	−0.76	0.71	−93.39	−0.17	0.59	−353.15	−0.59	8.98	0.004 *	0.18 S
Arm circumference at rest [cm]	0.51	0.49	96.19	0.19	0.28	148.08	0.32	7.07	0.011 *	0.14 S
Arm circumference under tension [cm]	0.91	0.89	97.27	0.30	0.47	159.60	0.61	8.31	0.006 *	0.17 S
Maximum forearm circumference [cm]	0.19	0.29	156.48	0.07	0.16	225.26	0.12	2.54	0.119	0.06 M
Minimum forearm circumference [cm]	0.11	0.16	141.88	0.05	0.38	760.33	0.06	0.52	0.474	0.01
Chest circumference at rest [cm]	0.71	0.72	101.17	0.14	0.36	255.09	0.57	11.09	0.002 *	0.21 S
Chest circumference on inhalation [cm]	0.88	0.69	78.34	0.15	0.34	232.15	0.73	20.09	<0.001 **	0.32 S
Chest circumference on exhalation [cm]	−0.15	0.31	−204.45	0.19	0.52	274.29	0.04	6.94	0.012 *	0.14 S
Chest mobility [cm]	1.03	0.49	48.18	−0.05	0.74	−1619.12	0.98	32.19	<0.001 **	0.43 S
Waist circumference [cm]	−0.71	0.81	−114.19	−0.60	0.62	−103.89	−0.11	0.27	0.606	0.006
Hip circumference [cm]	0.31	0.55	174.99	−0.20	1.18	−601.75	0.11	3.38	0.073	0.07 M
Maximum thigh circumference [cm]	1.50	0.97	65.11	0.09	0.28	312.81	1.41	42.18	<0.001 **	0.50 S
Maximum lower limb circumference [cm]	0.50	0.48	95.24	0.05	0.35	694.88	0.45	12.93	<0.001 **	0.24 S
Minimum lower limb circumference [cm]	0.20	0.26	134.42	−0.04	0.21	−566.42	0.16	10.61	0.002 *	0.20 S
Subscapular skinfold thickness [mm]	−0.40	0.45	−111.72	−0.35	0.44	−126.78	−0.05	0.16	0.688	0.004
Triceps skinfold thickness [mm]	−0.31	0.55	−176.62	−0.09	0.26	−297.46	−0.22	3.00	0.091	0.07 M
Biceps skinfold thickness [mm]	−0.16	0.26	−163.06	−0.05	0.15	−323.67	−0.11	3.19	0.081	0.07 M
Suprailiac skinfold thickness [mm]	−0.50	0.45	−90.58	−0.13	0.50	−391.87	−0.37	6.63	0.014 *	0.14 S
Abdominal skinfold thickness [mm]	−1.19	1.09	−91.61	−0.95	1.03	−108.22	−0.24	0.55	0.463	0.01
Calf skinfold thickness [mm]	−0.12	0.18	−155.88	0.02	0.09	382.42	−0.10	10.53	0.002 *	0.20 S
Sum of skinfolds [mm]	−1.21	1.27	−104.74	−0.56	0.78	−137.71	−0.65	4.15	0.047 *	0.09 M
BMI [kg/m2]	−0.24	0.22	−94.03	−0.05	0.19	−372.87	−0.19	8.77	0.005 *	0.17 S
Slenderness index [dq]	0.13	0.14	104.14	0.03	0.11	396.93	0.10	7.66	0.008 *	0.15 S
Arm muscularity [dq]	1.48	1.42	96.50	0.58	0.83	144.43	0.90	6.54	0.014 *	0.13 M
Forearm muscularity [dq]	0.70	1.10	157.18	0.28	0.62	219.63	0.42	2.43	0.126	0.55 S
Thigh muscularity [dq]	2.60	1.76	67.70	0.17	0.52	308.76	2.43	38.68	<0.001 **	0.48 S
Lower limb muscularity [dq]	1.33	1.30	97.89	0.11	1.01	936.27	1.22	12.02	0.001 *	0.22 S
FM %	−1.76	1.44	−81.52	−0.30	0.86	−288.50	−1.46	16.74	<0.001 **	0.28 S
FM [kg]	−1.55	1.19	−76.53	−0.26	0.77	−296.24	−1.29	18.36	<0.001 **	0.30 S
LBM [kg]	0.79	0.67	85.15	0.09	0.35	382.82	0.70	18.73	<0.001 **	0.31 S
Endomorphy [dq]	−0.12	0.13	−107.86	−0.06	0.08	−139.92	−0.06	3.39	0.073	0.07 M
Mesomorphy [dq]	0.26	0.23	89.48	0.06	0.12	178.16	0.20	12.03	0.001 *	0.22 S
Ectomorphy [dq]	0.06	0.06	104.14	0.01	0.05	396.93	0.01	4.00	0.052	0.09 M

$\tilde{x}$—arithmetic mean; sd—standard deviation; CV—coefficient of variation; dq—dimensionless quantity; d—difference between means (delta); F—statistic from the ANOVA test; p—level of significance for differentiation; η²—Eta-squared, measure of effect size * statistically significant values (p < 0.05); ** statistically significant values (p < 0.001); ^M moderate effect size; ^S strong effect size.

presents the characteristics of the training effects that occurred in the structural profile of the studied populations as a result of the experimental intervention. To isolate the baseline level of the variables, intergroup comparisons of delta changes were made—essentially, the differences in the achieved training effects between the studied groups.

The comparative analysis of means revealed significant differences for 22 structural variables, with more favorable results in the EXP group. This was most notable for functional characteristics such as chest mobility, circumferential features like maximum thigh circumference and, consequently, the thigh muscularity index, and variables characterizing fat levels (FM%, FM kg) and LBM (p < 0.001). The observed progressions and reductions also demonstrated a high effect size.

Table 5. Statistical characteristics of the structural profile and their intragroup variation in the studied groups (EXP n = 22; CON n = 22) of BJJ athletes (n = 44).

Variables	Measurement	Group EXP (n = 22)					Group CON (n = 22)
		$\tilde{\mathit{x}}$	sd	F	p	η2	$\tilde{\mathit{x}}$	sd	F	p	η2
Body weight [kg]	I pre-test	78.79	12.05	25.26	<0.001 **	0.55 S	77.88	9.86	2.79	0.111	0.12 M
	II post-test	78.03	11.86				77.71	9.69
Arm circumference at rest [cm]	I pre-test	31.00	3.27	23.78	<0.001 **	0.53 S	30.88	3.27	9.59	0.006 *	0.32 S
	II post-test	31.51	3.46				31.07	3.23
Arm circumference under tension [cm]	I pre-test	34.29	3.38	23.25	<0.001 **	0.53 S	34.13	3.46	8.11	0.010 *	0.29 S
	II post-test	35.29	3.78				34.42	3.39
Maximum forearm circumference [cm]	I pre-test	28.09	2.69	9.00	0.007 *	0.30 S	28.24	2.66	4.37	0.054	0.18 S
	II post-test	28.28	2.77				28.31	2.59
Minimum forearm circumference [cm]	I pre-test	18.45	1.59	10.93	0.003 *	0.34 S	18.50	1.54	0.46	0.508	0.02
	II post-test	18.56	1.67				18.55	1.58
Chest circumference at rest [cm]	I pre-test	92.05	8.92	21.50	<0.001 **	0.51 S	93.27	9.46	2.96	0.101	0.13 M
	II post-test	92.77	9.17				93.41	9.34
Chest circumference on inhalation [cm]	I pre-test	95.64	8.00	35.85	<0.001 **	0.63 S	95.99	9.31	3.58	0.073	0.15 S
	II post-test	96.51	8.11				96.13	9.25
Chest circumference on exhalation [cm]	I pre-test	90.09	9.06	5.26	0.032 *	0.20 S	89.85	9.20	3.11	0.093	0.13 M
	II post-test	89.94	9.10				90.04	9.24
Chest mobility [cm]	I pre-test	5.55	1.86	94.79	<0.001 **	0.82 S	6.14	1.44	0.14	0.709	0.01
	II post-test	6.57	1.93				6.09	1.46
Waist circumference [cm]	I pre-test	85.43	8.01	16.87	<0.001 **	0.45 S	85.30	7.98	19.65	0.001 **	0.50 S
	II post-test	84.71	7.55				84.90	7.56
Hip circumference [cm]	I pre-test	98.46	7.12	7.18	0.014 *	0.25 S	98.19	7.17	0.55	0.466	0.03
	II post-test	98.78	7.11				97.99	6.61
Maximum thigh circumference [cm]	I pre-test	56.55	4.05	51.90	<0.001 **	0.71 S	56.43	4.05	2.53	0.127	0.11 M
	II post-test	58.04	4.43				56.52	4.02
Maximum lower limb circumference [cm]	I pre-test	37.68	3.15	24.25	<0.001 **	0.54 S	37.43	3.09	0.55	0.469	0.03
	II post-test	38.18	3.37				37.48	2.99
Minimum lower limb circumference [cm]	I pre-test	23.09	2.05	12.18	0.002 *	0.37 S	22.97	2.03	0.53	0.477	0.03
	II post-test	23.28	2.22				22.93	1.95
Subscapular skinfold thickness [mm]	I pre-test	10.95	2.97	17.63	<0.001 **	0.46 S	10.83	2.94	12.01	0.002 *	0.38 S
	II post-test	10.55	2.63				10.48	2.66
Triceps skinfold thickness [mm]	I pre-test	7.73	1.20	7.05	0.015 *	0.25 S	7.62	1.19	2.23	0.151	0.10 M
	II post-test	7.42	1.08				7.54	1.20
Biceps skinfold thickness [mm]	I pre-test	4.45	0.75	8.27	0.009 *	0.28 S	4.39	0.76	2.11	0.162	0.10 M
	II post-test	4.30	0.56				4.34	0.74
Suprailiac skinfold thickness [mm]	I pre-test	10.68	2.86	26.81	<0.001 **	0.56 S	10.49	2.85	0.70	0.414	0.03
	II post-test	10.19	2.47				10.36	2.64
Abdominal skinfold thickness [mm]	I pre-test	12.50	5.06	26.21	<0.001 **	0.56 S	12.17	4.80	16.18	<0.001 **	0.45 S
	II post-test	11.31	4.03				11.22	4.08
Calf skinfold thickness [mm]	I pre-test	6.41	1.94	9.05	0.007 *	0.30 S	6.10	1.83	1.51	0.234	0.07 M
	II post-test	6.29	1.78				6.12	1.80
Sum of skinfolds [mm]	I pre-test	29.36	5.59	20.05	<0.001 **	0.49 S	28.94	5.51	9.64	0.006 *	0.33 S
	II post-test	28.15	4.58				28.37	5.06
BMI [kg/m2]	I pre-test	24.98	3.04	24.60	<0.001 **	0.54 S	24.86	2.71	2.65	0.119	0.12 M
	II post-test	24.74	2.99				24.81	2.67
Slenderness index [dq]	I pre-test	41.52	1.59	19.70	<0.001 **	0.48 S	41.53	1.57	2.15	0.158	0.10 M
	II post-test	41.65	1.58				41.56	1.56
Arm muscularity [dq]	I pre-test	90.71	6.81	23.65	<0.001 **	0.53 S	90.42	7.08	10.01	0.005 *	0.33 S
	II post-test	92.18	7.19				91.00	7.11
Forearm muscularity [dq]	I pre-test	105.15	6.39	8.89	0.007 *	0.30 S	105.20	5.86	4.63	0.044 *	0.19 S
	II post-test	105.85	6.92				105.48	5.63
Thigh muscularity [dq]	I pre-test	98.68	4.88	48.05	<0.001 **	0.70 S	98.44	5.13	2.58	0.124	0.11 M
	II post-test	101.29	5.64				98.60	5.24
Lower leg muscularity [dq]	I pre-test	99.66	12.15	22.97	<0.001 **	0.52 S	99.54	11.86	0.33	0.574	0.02
	II post-test	100.98	12.59				99.65	11.43
FM %	I pre-test	20.84	3.27	33.10	<0.001 **	0.61 S	20.91	2.18	3.50	0.076	0.15 S
	II post-test	19.08	4.17				20.61	2.12
FM [kg]	I pre-test	16.49	4.03	37.56	<0.001 **	0.64 S	16.23	2.38	3.45	0.078	0.15 S
	II post-test	14.94	4.19				15.97	2.37
LBM [kg]	I pre-test	62.29	9.26	30.31	<0.001 **	0.59 S	61.65	8.35	1.54	0.230	0.07 M
	II post-test	63.08	9.55				61.74	8.19
Endomorphy [dq]	I pre-test	2.85	0.60	12.96	0.002 *	0.38 S	2.81	0.59	7.19	0.014 *	0.26 S
	II post-test	2.72	0.50				2.75	0.54
Mesomorphy [dq]	I pre-test	6.40	1.10	28.46	<0.001 **	0.58 S	6.40	1.11	6.49	0.019 *	0.24 S
	II post-test	6.66	1.20				6.46	1.07
Ectomorphy [dq]	I pre-test	1.59	0.74	10.22	0.004 *	0.33 S	1.60	0.72	1.30	0.267	0.06 M
	II post-test	1.66	0.73				1.61	0.72

$\tilde{x}$—arithmetic mean; sd—standard deviation; CV—coefficient of variation; dq—dimensionless quantity; F—statistic from the ANOVA test; p—level of significance for differentiation; η²—Eta-squared, measure of effect size * statistically significant values (p < 0.05); ** statistically significant values (p < 0.001); ^M moderate effect size; ^S strong effect size.

presents the results and the direction of changes for the components of the structural profile that occurred as a result of the experimental intervention (pre-test vs. post-test) in the studied populations, as well as the degree of their intragroup variability.

The comparative analysis revealed significant differences (pre-test vs. post-test, p < 0.05) in favor of more favorable increases or reductions in all measurement variables within the EXP group.

The most noticeable changes were observed in chest mobility (mean increase $\tilde{x}$ = 1.03 cm), thigh circumference ($\tilde{x}$ = 1.50 cm), and muscularity indices: upper arm ($\tilde{x}$ = 1.48), lower leg ($\tilde{x}$ = 1.33), and thigh ($\tilde{x}$ = 2.60). Significant reductions were found for the following: FM% ($\tilde{x}$ = −1.76), FM kg ($\tilde{x}$ = −1.55), the sum of three skinfolds ($\tilde{x}$ = −1.21), and the endomorphic component of the somatotype ($\tilde{x}$ = −0.12).

In the CON group, after 8 weeks of the planned and implemented standard BJJ training, a trend toward significant improvement was observed in 10 out of 33 measured variables (p < 0.05). However, the progressions and reductions in this group showed weak effects and notably less favorable progressions compared to the EXP group (Table 5).

Table 6. Correlation coefficients between training experience and training effects (delta) in the EXP group.

Variables	Group EXP (n = 22)
	rs	p
Body weight [kg]	0.39	0.070
Arm circumference at rest [cm]	−0.77	<0.001 **
Arm circumference under tension [cm]	−0.70	<0.001 **
Maximum forearm circumference [cm]	−0.44	0.039 *
Minimum forearm circumference [cm]	−0.68	<0.001 **
Chest circumference at rest [cm]	−0.81	<0.001 **
Chest circumference on inhalation [cm]	−0.79	<0.001 **
Chest circumference on exhalation [cm]	−0.70	<0.001 **
Chest mobility [cm]	−0.54	0.010 *
Waist circumference [cm]	0.42	0.054
Hip circumference [cm]	−0.45	0.035 *
Maximum thigh circumference [cm]	−0.56	0.006 *
Maximum lower limb circumference [cm]	−0.38	0.085
Minimum lower limb circumference [cm]	−0.27	0.226
Subscapular skinfold thickness [mm]	0.26	0.250
Triceps skinfold thickness [mm]	0.64	0.001 *
Biceps skinfold thickness [mm]	0.52	0.012 *
Suprailiac skinfold thickness [mm]	0.37	0.094
Abdominal skinfold thickness [mm]	0.34	0.121
Calf skinfold thickness [mm]	0.63	0.002 *
Sum of skinfolds [mm]	0.49	0.021 *
BMI [kg/m2]	0.37	0.093
Slenderness index [dq]	−0.33	0.137
Arm muscularity [dq]	−0.76	<0.001 **
Forearm muscularity [dq]	−0.44	0.040 *
Thigh muscularity [dq]	−0.50	0.017 *
Lower limb muscularity [dq]	−0.38	0.082
FM %	0.57	0.005 *
FM [kg]	0.56	0.006 *
LBM [kg]	−0.67	<0.001 **
Endomorphy [dq]	0.49	0.022 *
Mesomorphy [dq]	−0.66	<0.001 **
Ectomorphy [dq]	−0.32	0.136

r_s—value of the correlation coefficient Spearman; dq—dimensionless quantity; p—level of significance; * a statistically significant level of differentiation (p < 0.05); ** statistically significant values (p < 0.001).

presents the correlation coefficients between the duration of training experience and the level of training effect increments from the experimental intervention within the EXP group.

For the circumferential variables, clear relationships were found for the upper arm (both at rest and under tension) and chest circumference at inhalation, exhalation, and in the neutral position (statistically significant correlations with very high strength and negative direction, in the range of r_s = −0.70 to −0.79). For thigh circumference, the smallest forearm circumference, and chest capacity, the same trend with high strength was observed (r_s = −0.54 to −0.68).

Reverse-positive significant relationships were observed for skinfolds, specifically for the biceps, triceps, and calf skinfolds (high strength; r_s = 0.52 to 0.64).

Regarding muscularity indices, statistically significant negative correlations were found for the upper arm (very high strength) and thigh (high strength).

For tissue components such as FM%, FM kg (positive correlations), LBM, and the mesomorphy component (negative correlations), significant relationships with high strength were noted.

4. Discussion

New, unconventional training stimuli are commonly used in many sports to optimize the overall training process [41,42,43,44,45]. To the best of the authors’ knowledge, this study was the first to evaluate the effectiveness of a programmed, experimental 8-week training program on the structural profile of athletes training in Brazilian jiu-jitsu (BJJ) at a competitive level. The key findings of this study revealed that the Grappler Quest (GQ) program comprehensively contributed to improving the structural aspects of the athletes in the EXP group, specifically regarding more favorable levels of circumferential characteristics, anthropometric indicators, skinfolds, tissue components, and somatotypes. However, this strategy led to significant structural progress only in the experimental group (Table 5). Nonetheless, the applied analysis of progressions and reductions (delta t-test, Table 4) highlighted statistically significant differences in training effects between the groups. Another important finding was the relationship between the applied experimental stimulus and the studied population. It was demonstrated that less training experience in the participants was significantly associated with a higher level of training effect.

BJJ performance is determined by weight limits (excluding the Open/Absoluto divisions), which encourages the search for ways to optimize one’s body composition, including minimizing body fat while increasing the development of both the structure and function of the muscular system [20]. In other prestigious combat sports disciplines, the benefits of using innovative training stimuli (e.g., a combination of resistance, aerobic, and other exercises) are well recognized both scientifically and practically [12,46,47]. A thorough analysis of the literature identified a gap in exploring this area within the BJJ environment. In order to foster the further development of the discipline, an attempt was made to fill this gap. Therefore, the hypothesis was put forward that an intervention based on incorporating resistance, gymnastic, flexibility, and BJJ-specific exercises in small exercise circuits would likely contribute to optimizing the quality of the structural profile of the athletes studied.

Indeed, the applied GQ program confirmed this hypothesis. The analysis of intragroup variation in the EXP group showed significant progressions (Table 5) for all circumferential characteristics (p < 0.05). The intervention led to consistent improvements across multiple muscle circumferences, with the most pronounced changes observed in the thigh and upper arm. Similar trends in training effects have been observed in various studies across different disciplines that investigated the effectiveness of experimental programs combining resistance training with diverse exercise contents and forms of implementation [48,49,50,51]. Interestingly, for chest circumferential variables, progress was observed for the neutral position and inhalation, while a regression was noted during exhalation, which presented a somewhat different trend compared to traditional ju-jitsu athletes, where interventions led to increases for all positions, including exhalation [49]. The decrease in exhalation circumference may have indicated that the intervention contributed to enhancing the strength of exhalation muscles (abdominal, internal intercostals) and improved the ability to more efficiently empty the lungs [52]. It is also interesting that GQ caused an increase in chest capacity by 1.03 cm (pre-test 5.60 vs. post-test 6.63). This structural–functional feature is an important indicator of respiratory function, and the literature indicates reference norms ranging from 3.5 to a maximum of 6 cm [53], although some sources even report values up to 12 cm [52]. Therefore, it was clear that the results for the stimulated athletes exceeded normative values. GQ improved the flexibility of respiratory muscles, thereby enhancing the respiratory system’s efficiency, which is considered highly important in BJJ activity [54]. Unfortunately, the lack of reports in the sports environment for this variable limited a broader discussion on this aspect.

In parallel with the increase in muscle circumferences, a significant increase in the muscularity indices (WU) of the limbs, which operationalize the ratio of circumference to bone length, was observed in the athletes of the EXP group. Consequently, significant benefits were noted in terms of LBM. For somatotype components, the endomorphy component showed a decrease while mesomorphy increased (Table 5). Our findings align with those of Tan et al. [51], where both the resistance training group (strength exercises only) and the combined training group (strength exercises combined with aerobic exercises) showed progress within the groups, including for LBM, after an 8-week intervention. Interestingly, the combined training group exhibited a significant and larger progression, along with a decrease in body weight [51]. Our findings are also highly relevant from a tactical perspective in this activity, in relation to the individual fighting model [55]. A review of the literature on the BJJ environment has shown that athletes with a higher mesomorphic component exhibit a greater ability to finish fights early [20], which is highly valued in the circles and community of this discipline.

In our own study, the fat tissue variables, measured with skinfold calipers, also showed favorable reductions, resulting in a desired improvement in the indices operationalizing global fat mass (sum of three skinfolds; FM%; FM kg). These findings are consistent with those of Ribeiro et al. regarding BJJ athletes [56], as well as athletes from other combat sports subjected to experimental interventions [57]. This reflects an improvement in the multidimensional reduction of fat in the athletes of the EXP group, which may have significant implications for their training and competition activities. Thematic reports for BJJ suggest that elite BJJ athletes tend to have a lower body fat percentage compared to non-elite athletes [58]. An interesting observation in this regard was made by Báez et al., who noted that the fighting style may require different body types, as athletes aiming to finish the match before the time limit (via submission) had a lower body fat percentage than those focused on maintaining a points lead [59]. Moreover, in other combat sports, such as judo, a higher body fat percentage negatively correlates with performance in mobility and technical tasks [20]. Our results also showed similarities with populations exposed to resistance and combined training, where post-test reductions in both percentage and total fat mass were noted. In those studies, the combined training (experimental) group showed statistically significant changes [59]. Similarly, Omorczyk et al. demonstrated significant reductions in skinfolds on the arm, scapula, and abdomen, as well as for global FM%, in basketball players subjected to a 6-week circuit resistance training program [50]. Additionally, Ambroży’s research team observed similar trends (6-week intervention) for fat tissue component variables in a group of competitive traditional ju-jitsu athletes [49].

It should be noted that the athletes in the CON group also showed progress (within the group), with significant results for selected variables. A significant increase was observed for 10 aspects describing the structural profile (p < 0.05). This suggests that the structure of BJJ training and the complexity of conducting sports combat in this discipline determine the development of morphological characteristics in athletes. However, there were fewer significant progressions, and they were characterized by lower effect strength. This suggests that traditional training methods, while beneficial, may not be sufficiently effective at every stage of periodization when it comes to optimizing key structural traits that determine optimal training and competition function [58].

The direct intergroup comparison with the randomized controlled trial did not reveal significant changes (p > 0.05) (Appendix A: Table A2). However, it is noteworthy that the scale and consistency of these benefits were different. The EXP group showed more favorable final levels for the measured variables (out of 33 variables, 24 were more favorable), reversing the trend observed before the intervention in comparison to the CON group (out of 33, only 11 were more favorable). The applied analysis for isolated intervention effects clearly highlighted significantly more favorable changes in the morphological characteristics of the athletes in the EXP group. Moreover, these changes exhibited a high effect size (Table 4). At this point, it is important to emphasize that further intervention efforts may be necessary, involving longer application periods of the discussed or similar stimuli, to verify the potential for generating even stronger training adaptations with more pronounced changes [59]. On the other hand, prolonged exposure could lead to a risk of disrupting data consistency, possibly resulting in some participants not completing the training. Previous studies have used longer intervention times, leading to mixed results, significant in some studies but not in others [60]. Interestingly, our results allow for the identification of directional trends for optimizing the structural profile (reducing the level of differences or increasing them, as well as shifting the level to a more favorable one compared to the pre-test) in the EXP group, compared to the control group. The better results of the EXP group suggest that GQ offers additional benefits beyond standard training practices.

The applied experimental combination of the training stimulus had a comprehensive impact on the EXP group, causally linked to the Grappler Quest (GQ). This level of impact was not observed in the CON group, which followed the path of standard BJJ training. Therefore, it is recommended to incorporate GQ into the broad periodization of the training process, specifically its application in the “optimal window” of the preparatory phase within the macrocycle. The results of this study indicate that innovative approaches (scientifically unexplored, empirically untested, or not widely available) lead to a more effective optimization of key structural determinants for training and competition activities while traditional training often fails to provide sufficient stimulation for maximum adaptation of athletes’ potential. The adaptations observed following the use of the GQ protocol may be closely linked to improvements in selected components of physical fitness and performance [2], which are essential for effectiveness in BJJ, both at the competitive and recreational levels [33]. This direction represents the focus of our further exploration.

In relation to the relationship between training experience and the effect of structural progression from the intervention, the current study demonstrated a greater impact of the stimulus on participants with shorter training experience (Table 6). In particular, this was evident for variables related to muscle mass (circumferential characteristics, muscularity indices, mesomorphy component). This suggests that, for athletes with higher training experience, achieving greater progress may require the application of higher-intensity exercises, longer exposure periods, or combinations of these independent variables, which warrants further research exploration.

The structural adaptations observed in the EXP group may be explained by the combination of high-intensity, multi-joint exercises with repeated bouts of anaerobic effort performed on an aerobic-demand platform, as characteristic of the GQ protocol. This comprehensive stimulus promotes hypertrophic and metabolic responses while also contributing to improved respiratory muscle function. It is also known that such effectiveness tends to be more pronounced in less experienced trainees, which is attributed to their greater adaptive responsiveness to training interventions [2]. It should also be noted that the use of indirect methods in our study represented a limitation, as it may have introduced a certain degree of measurement error. Furthermore, the sample consisted exclusively of young male athletes, and the results should not be generalized to females or older populations.

From a practical perspective, the GQ protocol can be integrated into BJJ training cycles as a complementary, morpho-functional method. It may be particularly useful during the general preparation phase or the pre-competition period, when enhancing structural readiness is especially beneficial [2,30]. Coaches can adjust the frequency and intensity of the program to align with technical and tactical training, providing athletes with advantages in terms of improved morphological—and potentially functional—adaptations. Such interventions may also have significant implications for the functional profile [2]. The periodization of GQ, in combination with regular sparring and technical–tactical training, may optimize athletic performance, highlighting its practical value within the broader training process.

Limitations of the Study

Although the study was carefully designed and conducted, it is important to note certain limitations that may affect the generalizability of the study results and require caution when interpreting the findings. One such limitation was the sample size. Although it was carefully calculated using statistical power analysis, a larger sample size could have increased the statistical power of the study and reduced the risk of Type II errors. Another limitation (in terms of achieving maximum precision in assessment) was that indirect methods were used to assess changes in muscle mass components (observed hypertrophy) and fat tissue (observed reduction), such as circumferential measurements and skinfolds, which are also based on estimation models (operationalizing global measures) and are prone to measurement errors. However, standardized measurement techniques were used, the procedures were carried out by an experienced researcher following a strict protocol, and the obtained results are scientifically justified. In future research, it is recommended to use objective methods for measuring tissue components (DEXA, MRI), which could provide comparisons and potentially even more accurate measurements. Furthermore, the specific profile of the participants (BJJ athletes) may limit the ability to generalize the results to other populations of grappling athletes (e.g., judo, wrestling, sambo, sport grappling, or ju-jitsu ne-waza). The blinding of the coaches and evaluators was not feasible and constituted a methodological limitation. Additionally, the sample consisted exclusively of adult male participants. To capture a more comprehensive context of the problem, future studies should expand the diagnostic scope to include a larger number of participants, other age groups, and female athletes. We assessed only the structural profiles, without analyzing physical fitness components. Sex-based comparisons were also not included and should be considered in future research. Finally, it is recommended to conduct interventions with other representatives of grappling combat sports.

5. Conclusions

Our results provide scientific evidence of the causal relationship between the Grappler Quest training program and the structural profile of BJJ athletes. This study showed that the circuit-based intervention effectively and multidimensionally improved the structural profile of BJJ athletes. The athletes in the EXP group, compared to the CON group, achieved more favorable post-test levels for structural variables. The intergroup and intragroup analyses showed that this progression was accompanied by significant hypertrophy, an increase in lean body mass, and a reduction in fat tissue variables in the EXP group, with a strongly significant improvement. Such improvements were not observed in the control group, suggesting that standard BJJ training may not optimally prepare athletes at all stages of long-term training. Ultimately, GQ, as a circuit-based combination of resistance exercises with BJJ-focused content, demonstrated greater overall effectiveness in optimizing the structural characteristics of athletes compared to standard training methods. This approach highlights the benefits of seeking and then implementing innovative training interventions to maximize the optimization of determinants of training activity and athletic performance outcomes. Interestingly, GQ produced stronger positive effects in athletes with less training experience. Therefore, the causality relationship concerning the higher impact on groups of athletes with more training experience (more intense stimulus, longer exposure to the intervention?) remains an open question, which warrants further scientific exploration.

Practical Implications

The 8-week Grappler Quest training program can be considered an effective practical approach for shaping and improving the structural profile of BJJ athletes. The results have valuable practical implications for coaches and athletes in this sport. GQ can be safely applied in training environments. It is recommended for use in training practices and should be further tested in other age groups, female athlete populations, and larger sample sizes. Furthermore, the GQ intervention flow should be applied to other combat sports disciplines, both grappling-based (e.g., judo, wrestling, sambo) and striking-based in the standing position (boxing, kickboxing, Muay Thai), as well as those that involve mixed standing and ground phases (MMA, sport jiu-jitsu). However, the modification of the exercise content to suit the specific discipline is recommended. In broad coaching control, GQ can significantly contribute to achieving optimal training goals, which can ultimately lead to significantly higher athletic performance outcomes.