Does the Physiological Response of a Triathlete Change in the Use or Absence of Drafting?

Background: Currently, tactics play an important and decisive role in sprint distance triathlons. One of the most decisive tactical elements is drafting in the cycling sector, depending on whether or not it is allowed by the test regulations. The objective was to analyze the physiological responses in running, in relation to drafting in the cycling sector, according to level and sex. Methods: To do this, a total of n = 44 subjects were divided into two levels (elite: they got a podium in the national championship, 15.68 ± 0.82 years; amateurs: they compete at the regional level, 15.68 ± 1.62 and 37.9 ± 1.74 years), undergoing two training sessions of four cycling-running multitransitions with variability in the permissibility of drafting were analyzed. A descriptive analysis of the variables was carried out, together with an inferential analysis to know the relationships and associations between the dependent and independent variables. Results: The results showed significant differences in the parameters, as related to running technique, heart rate, speed, and displacement (both between levels and sex). Conclusions: This study concludes that drafting in the cycling sector generates decisive physiological responses for the running sector.


Introduction
Triathlon is an Olympic sport that involves the performance of three sports disciplines (swimming, cycling, and running), which are carried out in order and without interruption, thus offering a wide variety of disciplines and distances [1]. According to current literature, the sprint distance is the one that enjoys the greatest popularity among popular triathletes, or age groups, because it requires less physical demand and can be within the reach of the majority of the population, without needing volumes of high training, such as the middleand long-distance, which are difficult to combine with work and social life for amateur athletes [2].
As a sport, a triathlon encompasses different modalities collected under the regulations of the Spanish Triathlon Federation, also known as FETRI [3], such as duathlon, cross duathlon, winter triathlon, or quadriathlon, among others. All these official competitions are organized according to the category of the participant. The regulation has an absolute male category and another absolute female category. In turn, these categories (according to sex) are divided according to the age of the participants [2].
All these modalities that are grouped within the triathlon, have a set of common norms or rules, such as the use of drafting or the distance of the test, which is related to the age of the participants. Younger participants will only be able to participate in short-distance events, while adults can participate in both short-and long-distance [3]. To do this, depending on the test to be performed, the preparation of the athlete will be modified. In this line, training planning is of great importance, since it must be oriented and based on the training principles: (i) supercompensation; (ii) overload; (iii) specificity; (iv) individualization; (v) variation; (vi) recovery; (vii) progression; and (viii) reversibility [4]. In addition, one of the main objectives of planning is related to the quantification of the load. The quantification of the load is the method used to know the volume and intensity to which athletes are subjected, thus being vital to achieve the objectives and physiological adaptations proposed in any sports planning [5].
Good load control and correct interpretation provide the coach with a set of reliable information regarding how the training process is affecting the athlete [6,7] and if the load planned for the athlete based on their needs and characteristics is causing the necessary or planned adaptation [8]. Traditionally, individual sports have focused part of their efforts on the control and quantification of the loads that these athletes support during training or competitions, with the aim of improving and planning training [9]. This trend has spread to other sports, currently being a booming issue in recent years [10]. However, in a large part of individual sports, this process has hardly changed, and technology can help both in the evaluation and quantification of daily work to optimize performance [11]. In this line, training groups are often seen, in which athletes with different objectives, moments of the season, age, or even competitive level are mixed; training in situations far from those that can be found in competition. In addition, in most competitions there is little knowledge of the competition that does not allow either coaches or athletes to predict the final result [12]. To do this, the tactic or approach of the competition is used. In this part, it is necessary to attend mainly to the regulations and, from there, look for a situation that most favors the athlete. In recent years, one of the trends in triathlons has been the use or prohibition of drafting, defining this fact as the situation of an athlete who during the competition is close to another cyclist who is ahead and takes advantage of his situation to reduce his physical-physiological demands to gain an aerodynamic advantage [13] (benefit from a possible decrease in resistance), and this variant may alter the final result of the competition. For this, the reproducibility of this situation in the training sessions in the organization of the competition is very important. This variant can alter the final result in the competition, and the reproducibility of this situation is very important in training, in order to organize the competition.
We reviewed the literature, and there are documents that analyze the different modalities of triathlon (in a generic way) or some specific sector [6][7][8][9][10]. However, there are no documents that analyze the influence of the cycling sector on the running sector and how drafting affects the triathlete's fatigue and technique. For all these reasons, the objectives of this research were: (i) to characterize the physical demands that triathletes endure in multi-transition training; (ii) analyze the differences in the demands they support according to the competitive level, sex, and type of circuit (with drafting/without drafting), according to the origin of the selected variables (internal load and external load variables).

Design
Following the classification model established by this research, we can frame it under a manipulative strategy, within studies of an empirical nature of a quasi-experimental nature, where we seek to examine the differences between groups of athletes, being a non-equivalent group design [14].

Sample
The sample of participants selected for this research corresponds to the non-random type, characterized by the influence of the researcher who selects the sample, and the choice made may be due to different factors. Within this group, it belongs to the intentional or opinion types, where the sample is chosen based on the study to be carried out and where representative samples are sought. A total of 44 triathletes (n = 44) included between the young category and the senior age group, both male and female, were analyzed (Table 1). All the selected triathletes train and compete regularly. On the one hand, there is the performance group made up of high-performance triathletes (they are the best triathletes in their categories-in young triathletes, they obtained a podium in the national championship; in adults, triathletes placed 15th or better in the national championship). On the other hand, the amateur/amateur group corresponds to triathletes from different clubs that compete in the regional triathlon league.

Materials and Instruments
Anthropometric characteristics were recorded using a portable rod stadiometer (SECA, Hamburg, Germany) and bioimpedance balance to record body composition using 8 model MC-780MA electrodes (TANITA, Tokyo, Japan). To record the variables related to the load borne by the athletes, each athlete was equipped with a WIMU PROTM inertial device (RealTrack Systems, Almería, Spain), which was attached to the athlete's body by means of an anatomically adjustable harness for practice, as well as a fitness tracker and GARMIN heart rate strap (Garmin, Olathe, KS, USA). The inertial device was used in the analysis and recording of the kinematic variables of distance and time, of accelerometry and neuromuscular. The heart rate band was for variables related to objective internal load (heart rate). To know the beginning and end of each athlete's test, an ANT+ transmitter was used that incorporated a button to mark the start and end points on the timeline of the devices [15].

Variables
The load variables are those that allow the coach to have a quantification of the demands that training causes in the athlete. Within the variables, one can differentiate between independent and dependent variables. In this research, the independent variables were sex (men and women), competitive level (amateur/amateur and elite), and circuit type (with and without drafting). The rest of the variables, defined below, are dependent: Variables related to the cycling sector: Average speed cycle sector (avg speed cycle): the average speed at which the athlete moves during his cycling phase, measured in km/h.
Variables related to the running sector: (ii) Time: time used by the athlete to cover the estimated distance of the running phase (400 m), measured in seconds [11,16,17] (v) Maximum heart rate (HRMax): maximum number of beats made by the heart in one minute, measured in beats per minute (bpm).

(vi)
Average heart rate (HRAvg): average number of beats made by the heart in one minute, measured in beats per minute (bpm). (vii) % Maximum heart rate (% HRMax): percentage at which the heart works, taking the maximum heart rate into account. It is a variable of intensity. (viii) Average speed (Speed avg): average speed at which the athlete has moved in a period during the running phase. (ix) PlayerLoad (PL): a vectorial magnitude derived from triaxial accelerometry data that quantifies motion at high resolution. Accelerations and decelerations are used to construct a cumulative measure of the rate of change in acceleration. Cumulative measure (PL) and intensity measure (PL·min −1 ) were used, thus being able to indicate the rate of stress to which the player submits his body during a given period of time. As a unit of load, it has a moderate-high degree of reliability and validity [17,18]. Variables related to neuromuscular fatigue of the test: (xiv) CMJ Jump height (CMJ): maximum height reached during the CMJ jump, measured in centimeters [19].
The variables HRMax, HRAvg, % HRMax PL, and CMJ were used in other similar studies for the quantification of internal and external load [20,21].

Statistical Analysis
A descriptive analysis was performed for the analyzed variables (mean and typical deviation). Next, the criteria assumption tests were carried out through the normality assumption (Shapiro-Wilk), homoscedasticity assumption (Levene test), and randomization assumption (Runs test), finding a distribution of the data as parametric [22]. In addition, an inferential analysis was performed to determine the differences based on the independent variable. For this, the selected test was t test for independent samples [23]. The value of significance used in the investigation was p < .05, according to the specification of Field [22]. The software used was the statistical package for the social science (SPSS Statistics, version 24, IBM Corporation, Armonk, NY, USA).

Procedure
Firstly, the territorial triathlon federation, where the investigation was going to be carried out, was contacted. Once the proposal was accepted, the technicians involved were informed of the research design (some of their triathletes could be part of the final sample). In addition, for minor triathletes, the parents were informed, who, through an informed consent, authorized the participation of their children in the research. Next, a contact was made with the athletes, so that they could experience the investigation procedure and materials that they were going to wear.
The study consisted of performing two multi-transition training sessions with a separation of 2 weeks (the same training strategies, nutrition, recovery, and accumulated weekly training load were maintained, an attempt was made to reproduce them in both evaluations). Each multi-transition training will be divided into four cycling and running transitions, with a total recovery of 10 min between each transition, in order to analyze the parameters with the least possible wear. Each cycling circuit will have a distance of 2000 m, and each running circuit will have a distance of 400 m. Both circuits will take place on asphalt, with the aim of reproducing competition conditions. In test 1, drafting was prohibited. Each triathlete started individually, with a margin of 1 min between the next subject to start the transition.
In test 2, drafting was allowed. The outputs were achieved in groups of 10, in order to reproduce competition situations. The circuits used in both evaluations were the same, so that the circuit was not a polluting variable. In each training, the triathletes used the same sports material and nutrition and hydration system. In addition, the day chosen for the test was the same day of the week, and the load accumulated during the week in both situations was similar.

Results
The results of the investigation, according to the independent variables, are presented below. Table 2 below shows the descriptive results and significant differences between sex in the circuit without drafting, as differentiated in each of the four transitions of the elite athletes. In transition 1, significant differences are shown in the distance traveled at different speeds, as well as the flight time related to the running technique. In transition 2, significant differences are shown in the distance covered at different speeds and jump height CMJ, related to fatigue. In transitions 3 and 4, significant differences are shown in the distance traveled at different speeds. Both in transitions 2, 3, and 4, no significant differences were observed in the variables related to running technique for elite level athletes.  It also analyzes the differences between sex in the circuit without drafting at the amateur level divided into the four transitions. In transition 1, significant differences were found in the distance traveled at different speeds, explosive distance, heart rate variables, and PlayerLoad. In transition 2, significant differences were found in the distance traveled at different speeds, heart rate variables, and average running speed. In transition 3, significant differences were found in the variables of heart rate, PlayerLoad, and average speed of the running phase. In transition 4 significant differences were found in the distance traveled at different speeds. In addition, in the 4 transitions carried out, significant differences between sex were observed in the amateur athletes in the variables related to running technique. Table 3, below, shows the descriptive results and the significant differences between sex in the circuit with drafting, as differentiated in each of the four transitions of the elite athletes. In transition 1, significant differences are shown in the explosive distance, heart rate variables, and PlayerLoad. In transition 2, significant differences are shown in the distance traveled at different speeds, average speed of the running phase, and PlayerLoad. In transitions 3 and 4, significant differences are shown in the distance traveled at different speeds, heart rate variables, average speed of the running phase, and PlayerLoad. In addition, in transitions 1, 2, and 4, significant differences were observed in the variables related to running technique for elite-level athletes.  The differences between sexes in the circuit with drafting at the amateur level divided in the four transitions were also analyzed. In transition 1, significant differences were found in the distance traveled at different speeds. In transitions 2 and 3, no significant differences were found in the variables analyzed. In transition 4, significant differences were found in the number of steps made. Finally, in this modality with drafting, differences were observed at the elite level in most transitions when fatigue was evaluated (through the CMJ jump). Table 4 shows the results grouped according to the competitive level and use, or absence, of drafting during the four transitions. The results belonging to elite level athletes show that there are significant differences in the parameters of distance traveled at different speeds in transitions 1, 2 and 4. In addition, significant differences are shown in the variables related to the running technique (stride) in variables 2, 3, and 4. On the contrary, in the amateur-level subjects, significant differences are shown in the parameters of distance traveled at different speeds in transition 1. Finally, significant differences are also shown in the variables related to the running technique (stride) in variables 2, 3, and 4.

Discussion
The analysis and quantification of the load in training or competition in individual sports has been a common practice for many years. However, it is currently still evaluated or quantified with the same procedure, and very few incorporate new technology or parameters. In addition, on many occasions, the athlete is evaluated without paying attention to the test or format for which it is intended to prepare. That is why the characteristics of the test must have an impact on the preparatory process.

Differences between Sex in the Circuit with Drafting
The significant differences of the analyzed variables, according to sex in the circuit with drafting in elite-level athletes, showed the main finding of the research that the running technique and physiological variables vary heterogeneously, according to sex, with fatigue. These differences especially appear in the variables jump CMJ (assessment of fatigue) and the flight phase of the stride. In this line, Reilly [24] analyzed the difference in running technique between women and men in athletes. This study concluded by stating that the anatomical differences between a woman and man affect the development of the running technique. One of the most prominent causes is due to the fact that women have a wider pelvis than men, which affects the "Q angle" between the pelvis and femur [25,26]. This study also suggested that women's pelvises are more tilted than men's, inducing a forward curvature when running. The fact of not finding significant differences in the rest of the parameters is attributed to the sports level of the athletes analyzed, since, at these levels, women train at high volumes and intensities that allow them to perform in competitions at a high aerobic and anaerobic levels [27].
However, if the significant differences in the test performed by amateur-level athletes are analyzed, the main findings are the difference in the running technique in the flight phase (measured through 'tFly') that affects the difficulty to reach and maintain high running paces. Differences in running technique can be attributed to the anatomical differences in women, compared to men, as discussed above [25,26]. To analyze the differences in reaching high rhythms, the existing literature shows different studies related to specific training for women [28]. Along these lines, García [29] analyzed the physiological differences between men and women that must be taken into account when planning training sessions. According to this study, women should train for anaerobic thresholds at higher intensities than men, since their fat metabolism is higher and maintained at higher intensities than men. In addition, he suggested that, if men normally enter anaerobic consumption at 80-85% of their maximum heart rate, women should do so at 85-90% of their maximum heart rate, in the same way they are training in mixed aerobics instead of anaerobic. For all these reasons, different causes have traditionally been shown that made it difficult for women to reach high running rhythms, with the planning being carried out with a generic design and without taking their physiological or hormonal considerations into account, compared to those of men [30]. The fact that no significant differences were found in the rest of the parameters is related to the fact that, although the level is amateur, they are triathletes who compete regularly, and their energy systems are developed and stimulated to perform intense training [27,31,32].

Differences between Male/Female Sex in Circuit without Drafting
In the test carried out on the circuit without drafting, the elite athletes analyzed responded differently to the same stimulus, depending on their sex. Although there are differences related to running technique and anaerobic threshold, the main finding is the appearance of significant differences, as related to the other parameters of running technique and displacement (meters traveled at different speeds or step contact time), as well as the high % of maximum heart rate achieved. Coinciding with the findings mentioned above, the anatomical differences in women cause a change in the running technique, with respect to men, as well as the fact that our affected technical parameters appear can be associated with the fact that the wear associated with a circuit without drafting is higher than in a circuit with drafting. In this line, Melendo [33] stated that the energy wear of going to the wheel (drafting) is equivalent to a savings of 30%, due to factors related to aerodynamics. Concurring with the statement, Anderson [34] suggested that, in addition to aerodynamics, muscle mass also interferes with energy wasting because the greater the muscle mass, the greater the displacement and rolling force. According to body composition, women in this study have a higher percentage of muscle mass than men. This fact would justify a greater energy expenditure by women in this type of circuit that could harm the technical execution of the subsequent foot race [35][36][37]. In addition, the appearance of significant differences in the variables related to heart rate is also related to fatigue, body composition, and the wear and tear produced by the absence of writing [38]. This can generate poorly planned training (generic, without differentiating by sex or according to physiological factors), as well as training without being structured according to the woman's anaerobic threshold, which can cause greater physical exhaustion, thus justifying the findings obtained in this manuscript.

Differences in the Use/Absence of Drafting between Competitive Levels
Finally, the differences between elite and amateur athletes in the use or absence of drafting in physical demands have been analyzed. The main finding is the appearance of significant differences at both levels in parameters, as related to cardiac output, running technique (stride), and movement speed. To do this, Gutiérrez [39] analyzed the aerodynamic losses in cycling, based on the number of cyclists that make up a group and concluded that the fact of going in a group of five cyclists or more "on the wheel" implies an energy waste between a 20-30% less than in a circuit without drafting, where the mechanical and aerodynamic losses are greater. This fact justifies the differences in cardiac wear between one circuit and another. In addition, in relation to the variables, Calas [40] analyzed the biomechanical characteristics of different triathletes. This study concluded that there was previous wear in the swimming and cycling segments conditions running technique. This fatigue tends to make triathletes execute a pendulum running technique, instead of a circular one [41]. Caro [42] stated that the fatigue generated by swimming and cycling makes the arms swing less. In turn, the fatigue in the hamstring muscles generated in the cycling segment makes the support time longer and flight phase more less accentuated [32,43]. In line with the findings found, Coles et al. [44] determined that, in cycling situations where drafting is not allowed, oxygen consumption increases between 18-33% and lactate accumulation appears earlier than it does on circuits without drafting. This fact justifies the differences found in the high heart rate intervals that require a greater energy expenditure. Another study, Castellar [45] suggests a greater specialization of training, giving greater importance to race tactics, as well as an individualization of the race technique, depending on the competition circuit, and greater differentiation in training between men and women. The variation in the explosive distance in running is due to the muscular and physiological fatigue generated in the cycling sector [46]. According to Mon [47], the muscular fatigue generated by swimming and the cycling sector generates a loss of explosive force of 15% in international triathletes. These data are associated with the previous study [44], where energy and physiological expenditure without drafting is increased, which could justify this difference in explosive distance between the circuit with and without drafting.
This study provides a new point of view on the importance of good race tactics, in order to perform at the highest level in a triathlon. The fact that the cycling segment does not allow drafting has clear and direct consequences for the subsequent running race, regardless of the level of the triathlete. Increasingly, the ITU (International Triathlon Union) is betting on short and explosive test formats, where every second will be key to achieving good results. Having relevant data regarding how to improve and enhance running biomechanics and reduce cardiac output can be key in this type of test format. In turn, COVID-19 has generated some changes in the regulations, where many competitions were held with the individual time trial format where drafting was not allowed. This study highlights the increasingly pronounced importance of working on racing technique, according to the needs of the circuit and in an individualized way, starting from the lower categories. In addition, it provides useful information on the need for training and practical application of specific training differentiated for women and men. Training at the same intensities and structures as men has been shown to impair cardiac performance in demanding training and future competitions. This study suggests the need for greater training and specialization of coaches in the specific training of female athletes.
Inertial device technology has been used in a novel way, since there are hardly any cyclical sports studies that have used it, and it has served to provide clear information on biomechanical aspects of running on a field test and in a situation close to competition. This information facilitates the planning or detection of any anomaly, due to the fact that it has traditionally had a high cost, and not all athletes can access it. Finally, the application of this technology is suggested to carry out assessments and monitoring of cyclical sports, in order to optimize their performance in training and competitions. It also suggests working on the running technique in men differently than in women, taking the anatomical differences that they present into account. In addition, a limitation of the research is the number of the sample (n = 44), which is limited and has specific characteristics. It would be interesting to, in future research, expand the number of athletes analyzed (expanding in amateur and elite, both male and female).

Conclusions
The main conclusions confirm that the physiological demands supported are influenced by the sex, type of circuit, and level of the athlete. It is also concluded that drafting influences cardiac output in elite and amateur running. For this reason, it is concluded that the circuit without drafting generates a loss of explosive force in the running race, as reflected in the explosive distance and height of the jump. Additionally, drafting has a greater influence on women than men, based on steps/stride-related parameters (flight time, step time, and contact time). Drafting influences cardiac output in elite and amateur runners.
For all these reasons, taking the results obtained in the research into account, it is recommended that coaches and sports professionals, during the planning and development of training sessions, seek to prepare the athlete (regardless of sex or sports level) for the sport, physical activity, or effort that will be made during the competition-often, training groups are observed doing joint training (with the help of drafting), when, during the competition, that "extra help" is prohibited. Funding: This study has been partially subsidized by the Aid for Research Groups (GR21149) from the Regional Government of Extremadura (Department of Economy, Science and Digital Agenda), with a contribution from the European Union from the European Funds for Regional Development.

Institutional Review Board Statement:
The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of University of Extremadura for studies involving humans (233/2019).