Biomechanics

Background/Objectives: The objective of this study was to compare muscular strength and neuromuscular activation characteristics between male gymnasts and physical education (PE) students during isometric shoulder extension and flexion tasks. Methods: Thirteen competitive male gymnasts (age: 19.59 ± 1.90 years; body mass: 66.54 ± 6.10 kg; height: 169.38 ± 6.28 cm; mean ± SD) and thirteen male physical education (PE) students (age: 20.96 ± 2.30 years; body mass: 74.00 ± 8.69 kg; height: 174.96 ± 4.93 cm) voluntarily participated in the study. Peak torque (PT), rate of torque development (RTD), RTD normalized to body mass (RTD/BM), and muscle activation assessed via surface electromyography (EMG), normalized to maximal EMG activity (EMG/EMGmax), were evaluated during bilateral isometric shoulder extension and flexion at a joint angle of 45°. Measurements were analyzed across the following time intervals: −50 to 0 ms (pre-tension), 0–30 ms, 0–50 ms, 0–100 ms, and 0–200 ms relative to contraction onset. Custom MATLAB R2024b scripts were used for data processing and visualization. One-way and two-way multivariate analyses of variance (MANOVAs) were conducted to test for group differences. Results: Gymnasts exhibit higher values of PT, PT/BM, RTD, and RTD/BM particularly within the early contraction phases (i.e., 0–50 ms and 0–100 ms) compared to PE students (p < 0.05 to <0.001; η² = 0.04–0.66). Additionally, EMG activity normalized to maximal activation (EMG/EMGmax) was significantly greater in gymnasts during both early and mid-to-late contraction phases (0–100 ms and 0–200 ms), (p < 0.05 to <0.001; η² = 0.04–0.48). Conclusions: These findings highlight gymnasts’ superior explosive neuromuscular capacity. Metrics like RTD, RTD/BM, and EMG offer valuable insights into rapid force production and neural activation, supporting performance monitoring, training optimization, and injury prevention across both athletic and general populations. Full article

Background/Objectives: Body stability plays a decisive role in archery, particularly during the aiming phase. A systematic review was conducted, in accordance with PRISMA guidelines, to critically examine the existing evidence on the association between body stability parameters and shooting performance. Methods: A comprehensive search of the MEDLINE Complete, CINAHL Complete, SportDiscus, and Cochrane Reviews databases was performed. Studies published until 12 July 2024 were considered. Results: Sixteen articles were selected, and we analyzed the following biomechanical parameters related to body stability: center of pressure displacement, velocity, and ellipse area; bow sway; and sway of markers placed on the head, sternum, and pelvis. The findings consistently showed that reduced center of pressure displacement and velocity, along with smaller center of pressure ellipse area, were associated with superior shooting outcomes. Although studies are scarce, data suggest that lower bow sway is associated with better shooting performance. The scarcity of research on the sway of markers placed in anatomical points does not allow for conclusions about their effectiveness as performance predictors. Despite its relevance, no studies have assessed the center of gravity data. Therefore, further research is needed to address this important point. Conclusions: Although studies have examined several parameters, the literature remains inconclusive regarding which of these parameters best predicts shooting quality. Full article

Background/Objectives: Artificial tendons offer an alternative to biological tendon grafts and may restore normative biomechanical functions in humans and animals suffering segmental or complete tendon loss. The aim of this study was to quantify movement biomechanics during hopping gait and muscle properties of New Zealand White rabbits with a polyester silicone-coated (PET-SI) artificial tendon. Methods: In five rabbits, the biological Achilles tendon of the left hindlimb was surgically replaced with a PET-SI artificial tendon; five operated control rabbits underwent complete surgical excision of the biological Achilles tendon in the left hindlimb with no replacement (TE). Results: Across both groups at 2 and 8 weeks post-surgery compared to baseline, the maximum ankle angle during stance and swing phases of stride was significantly lower (i.e., more dorsiflexed) (p < 0.001), the peak vertical force was significantly higher (p < 0.001), and the average ground contact area was significantly lower (p < 0.001). At 8 weeks post-surgery, the muscle cross-sectional area of the lateral gastrocnemius was significantly higher in the PET-SI group than in the TE group (p = 0.006). Muscle mass and length were lower in the operated limb compared to the non-operated limb across the two groups (TE and PET-SI), with no significant differences between groups. Conclusions: The artificial Achilles tendon did not appear to provide superior biomechanical support during hopping compared to the TE group. However, the artificial tendon preserved muscle structural properties that correspond to the muscle’s capacity to generate force. Future studies should optimize the tendon–tissue interface. Full article

Background: Arthrodesis of the first metatarsophalangeal joint (MTP1) is a common intervention for hallux rigidus (HR). The procedure eliminates MTP1 motion but results in significant pain relief and high satisfaction rates, although MTP1 is eliminated. Less evidence is available regarding the effects on gait and the presence of compensatory mechanisms. The aim of this study is to investigate the effects of MTP1 arthrodesis on gait and patient-reported outcome measures (PROMs) compared with preoperative functioning and healthy individuals. Methods: In this prospective study, 10 patients (10 feet) with HR who underwent MTP1 arthrodesis were evaluated before and after surgery and compared with 15 healthy controls (30 feet). Gait analysis was performed with a motion capturing system using the multi-segment Oxford foot model. Spatiotemporal parameters and kinematics were quantitatively analyzed. PROMs were evaluated using validated questionnaires including the American Orthopedic Foot and Ankle Society Hallux Metatarsophalangeal-Interphalangeal (AOFAS-HMI) scale, the Numeric Pain Rating Scale (NPRS), and the Manchester–Oxford Foot Questionnaire (MOXFQ). Results: MTP1 joint motion was reduced in HR and further reduced after MTP1 arthrodesis compared with healthy controls. Furthermore, intersegmental ROM analysis revealed increased forefoot frontal plane motion (pronation and supination) in HR compared with healthy controls. This was also observed after MTP1 arthrodesis, while additionally increased frontal plane motion in the hindfoot (inversion and eversion) was observed compared with HR and healthy controls. PROM evaluation revealed improved AOFAS-HMI (from 55.7 to 79.1 points, p = 0.002) and NPRS (from 5.7 to 1.5 points, p = 0.004) scores after surgery. Additionally, improvements in the MOXFQ score (from 51.0 to 20.0 points, p = 0.002) were observed. Conclusions: Due to the loss of sagittal hallux motion, foot and ankle kinematics are changed in HR patients and after MTP1 arthrodesis compared with healthy controls. Loss of MTP1 motion results in increased frontal plane motion of the forefoot in HR, and increased frontal plane motion of the fore- and hindfoot after MTP1 arthrodesis. Additionally, substantial improvements in PROMs were recorded after surgery. Full article

Background/Objectives: This study evaluated the reliability and validity of three methods to measure jump height during countermovement jumps performed with (CMJ_AS) and without (CMJ_NAS) arm swing: (1) an impulse–momentum method with force platforms (FP_imp), (2) a flight time method with force platforms (FP_time), and (3) an inertial measurement unit (PUSH Band 2.0; PUSH2). Methods: Eighteen physically active men performed CMJ_AS and CMJ_NAS on force platforms while wearing PUSH2 over two days. Besides jump height, we computed intraclass correlation coefficients (ICC) and the absolute and relative increases in jump height due to arm swing, compared to CMJ_NAS. Results: The reliability of intra-session, inter-session, and concurrent measures were good to excellent (intra-session ICC_2,1 = 0.957–0.979, inter-session ICC_2,1 = 0.806–0.990, concurrent ICC_3,1 = 0.940–0.973) for CMJ_AS and CMJ_NAS heights, in all three methods. The three methods showed high to very high reliability for both the absolute and relative indices of arm swing contribution (ICC_2,1 = 0.649–0.812). FP_time significantly overestimated CMJ_NAS height relative to FP_imp (p < 0.01). The absolute index of arm swing contribution was similar in FP_imp and FP_time (p = 0.38) but higher in PUSH2 (p < 0.01), indicating that arm swing amplified overestimation. Conclusions: All three methods demonstrated high reliability for jump height measurements, but FP_time and PUSH2 misestimated jump height depending on jump modalities. Caution is advised when assessing the absolute and relative contribution of arm swing, because errors in CMJ_NAS and CMJ_AS height measurements can affect these values and their interpretation. Full article

Flexed and tensed arm (FTA) circumference is a fundamental anthropometric measurement for determining the mesomorphic component in somatotype. This study examined the impact of contralateral limb opposition (+OP) on arm circumference measurement and biceps brachii muscle activation. Fifty physically active men and women, mean (22.7 ± 2.9 years), participated in this study. FTA circumference measurements were taken with FTA + OP and without opposition FTA, following ISAK protocols. Additionally, biceps brachii muscle activation was assessed using surface electromyography (sEMG). Significant differences were identified in the flexed and tensed arm circumference (>1%) and in the mesomorphic component between the FTA and FTA + OP conditions (p < 0.001). In addition, contralateral limb opposition resulted in a significant average increase of 39.02% in biceps brachii muscle activation, with variations between 24.57% to 47.46% across the time intervals analyzed (p < 0.05). A moderate correlation was observed between the percentage difference in sEMG and arm circumference during the middle second of contraction (r = 0.418). However, during the first (r = 0.393), third (r = 0.376), and mean (r = 0.385) contraction periods, the correlation was considered weak. Contralateral limb opposition caused greater biceps brachii muscle activation, resulting in an increase in flexed and tensed arm circumference in physically active young adults. Full article

Background/Objectives: Walking coordination is crucial for maintaining independence and quality of life, but it is significantly affected by aging and cognitive decline. This study investigates how age and cognitive status relate to lower limb coordination during gait, using a network-based analysis of joint kinematics. Methods: Fifty-six healthy participants (31–82 years old) underwent gait analysis with a stereophotogrammetric system and cognitive assessment through standardized neuropsychological tests. Kinematic data were processed to build “kinectomes”, representing the inter-joint coordination across the gait cycle. Results: The results showed that the mean lower limb coordination on the sagittal plane negatively correlated with age and positively with cognitive performance. Detailed analysis revealed that age-related declines in coordination were primarily driven by reduced synchronization at the knees, while cognitive status was associated with overall coordination rather than joint-specific changes. Conclusion: These findings emphasize the knees’ critical role in preserving gait coordination with aging and underline the involvement of cognitive aspects in global coordination mechanisms. In summary, our network-based approach provides a refined perspective on gait dynamics, highlighting the relationship between coordination and both age and cognition. Full article

Background/Objectives: The assessment of relationships between trunk muscle activity and thoraco-lumbar movements during sagittal bending has demonstrated that low back pain (LBP) subgroups (flexion pattern and active extension pattern motor control impairment) reveal distinct relationships that differentiate these subgroups from control groups. The study objective was to establish whether such relationships exist during various daily activities. Methods: Fifty participants with non-specific chronic low back pain (NSCLBP) (27 flexion pattern (FP), 23 active extension pattern (AEP)) and 28 healthy controls were recruited. Spinal kinematics were analysed using 3D motion analysis (Vicon™, Oxford, UK) and the muscle activity recorded via surface electromyography during a range of activities (box lift, box replace, reach up, step up, step down, stand-to-sit, and sit-to-stand). The mean sagittal angles for upper and lower thoracic and lumbar regions were correlated with normalised mean amplitude electromyography of bilateral transversus abdominis/internal oblique (IO), external oblique (EO), superficial lumbar multifidus (LM), and erector spinae (ES). Relationships were assessed via Pearson correlations (significance p < 0.01). Results: In the AEP group, increased spinal extension was associated with altered LM activity during box-replace, reach-up, step-up, and step-down tasks. In the FP group, increased lower lumbar spinal flexion was associated with reduced muscle activation, while increased lower thoracic flexion was associated with increased muscle activation. The control group elicited no significant associations. Correlations ranged between −0.812 and 0.754. Conclusions: Differential relationships between muscle activity and spinal kinematics exist in AEP, FP, and pain-free control groups, reinforcing previous observations that flexion or extension-related LBP involves distinct motor control strategies during different activities. These insights could inform targeted intervention approaches, such as movement-based interventions and wearable technologies, for these groups. Full article

Objectives: Wheelchair seat sagging is hypothesized to increase pressure and shear forces, potentially leading to pressure injuries. The objective of this study was to assess the impact of correcting wheelchair seat sagging on ischial pressure, shear force, and posture in a population of healthy adults. Methods: A total of twenty-two participants who met the study requirements were included in the study. Participants were evaluated under two conditions: with seat base correction (With Correction) and without it (No Correction). Correction was achieved using insert panels. Ischial pressure was measured using a pressure-mapping system (CONFORMat), shear force with a specialized sensor (iShear), and posture with accelerometers (TSND151). The primary analysis compared peak pressure index (PPI), shear force, slide, and postural changes between conditions. The subgroup analysis was conducted as an exploratory approach to assess potential variation among participants with elevated shear forces. Results: There was no statistically significant difference in ischial pressure between the No Correction and With Correction conditions (p = 0.37). However, shear force and slide were significantly reduced when seat sagging was corrected (p < 0.05). Accelerometer data showed no significant difference in postural changes between conditions (p ≥ 0.05), although the With Correction condition displayed a slight trend toward greater positional variability over time. Conclusions: These findings indicate that correcting seat sagging can reduce shear force and slide, potentially lowering the risk of pressure injuries. However, because this study targeted healthy adults, further research involving older or at-risk populations is necessary. Addressing seat sagging could be an important component of comprehensive pressure injury prevention strategies. Full article

The running cycle is distinguished from the gait cycle by the presence of a flight phase and distinct biomechanical characteristics. Despite existing frameworks for the temporal segmentation of running, these models remain underutilized in comprehensive biomechanical analyses, particularly for delineating phases, subphases, and key events. This study aims to provide a review of historical and contemporary temporal models of the running cycle and to introduce a unified structure designed to enhance analytical precision. The proposed framework divides the running cycle into two primary phases: (a) contact (subdivided into braking and propulsion subphases) and (b) flight, together with three critical events: (1) initial contact, (2) transition of braking–propulsion, (3) toe-off. While leg swing is not considered a phase in this framework due to temporal overlap with other phases, its recognized importance in running mechanics warrants its integrated analysis under the proposed temporal phase delineation. Additionally, methodologies for identifying these events through dynamometry and motion capture are evaluated, emphasizing their role in contextualizing kinetic and kinematic data. By integrating this temporal structure, the study aims to standardize biomechanical assessments of running technique, fostering more consistent comparisons across studies. Such integration has the potential to not only refine interpretations of running mechanics but also to enable practical advancements in athletic training, injury mitigation, and performance optimization. Full article

Background/Objectives: Stroke survivors often develop asymmetric gait patterns that may lead to abnormal knee joint loading and potentially increased risk of osteoarthritis. This study aimed to investigate differences in knee joint loading between paretic and non-paretic limbs during walking in individuals post-stroke. Methods: Twenty-one chronic stroke survivors underwent three-dimensional gait analysis. A modified musculoskeletal model with a specialized knee mechanism was used to estimate medial and lateral tibiofemoral contact forces during the stance phase. Statistical parametric mapping was used to identify significant differences in joint kinematics, kinetics, and contact forces between limbs. Stepwise regression analyses examined relationships between knee moments and compartmental contact forces. Results: Significant differences in knee loading were observed between limbs, with the non-paretic limb experiencing higher medial compartment forces during early stance (6.7–15.1%, p = 0.001; 21.9–30.7%, p = 0.001) and late stance (72.3–93.7%, p < 0.001), and higher lateral compartment forces were recorded during pre-swing (86.2–99.0%, p < 0.001). In the non-paretic limb, knee extensor moment was the primary predictor of first peak medial contact force (R² = 0.573), while knee abductor moment was the primary predictor in the paretic limb (R² = 0.559). Conclusions: Musculoskeletal modeling revealed distinct asymmetries in knee joint loading between paretic and non-paretic limbs post-stroke, with the non-paretic limb experiencing consistently higher loads, particularly during late stance. These findings suggest that rehabilitation strategies should address not only paretic limb function but also potentially harmful compensatory mechanisms in the non-paretic limb to prevent long-term joint degeneration. Full article

Robotic cadaveric testing provides a controlled approach to studying knee ligament biomechanics under continuous motion, addressing limitations in static or mechanical loading testing. Our study describes an alternative method for soft-tissue strain measurement, followed by an investigation of this method on knee ligament strain and joint kinematics using a six-degree-of-freedom robotic system equipped with force and torque sensors. Six cadaveric knee specimens underwent controlled 90° flexion cycles, with uniaxial strain gauges sutured to the ACL, PCL, MCL, and LCL for strain measurement. Results indicate that the LCL exhibited the highest extension at 1.63 mm, while the ACL showed minimal extension at 0.09 mm. The MCL were at −0.76 mm and PCL at −1.76 mm contraction, suggesting a stabilizing function under flexion. Varus torque at 2.18 Nm at 90° flexion correlated with LCL strain, and PCL translation variability reflected its multi-planar engagement. These findings confirm ligament-specific strain responses under dynamic loading, highlighting that the LCL and PCL undergo the most significant length changes. Full article

Background/Objectives: This study aimed to investigate the skating determinants and differences between male and female bandy players in the spatiotemporal variables during acceleration and maximum sprint skating velocity. Methods: Seventy-four female bandy players (age: 18.9 ± 4.1 years; height: 1.67 ± 0.06 m; body mass: 63.2 ± 7.4 kg; training experience: 13.4 ± 3.9 yrs.; and 26 elite and 48 junior elite) and 111 male bandy players (age: 20.7 ± 5.0 years; height: 1.80 ± 0.05 m; body mass: 76.4 ± 8.4 kg; training experience: 13.8 ± 5.0 yrs.; and 47 elite and 66 junior elite players) performed linear sprint skating over 80 m. Split times were measured every ten metres by photocells to calculate velocities for each step and spatiotemporal skating variables (glide times and length, step length, and frequency) by IMUs attached to the skates. The first six steps (acceleration phase), the six steps at the highest velocity (maximal speed phase), and the average of all steps were used for analysing glide-by-glide spatiotemporal variables. Results: These revealed that male players exhibited higher acceleration and maximal skating velocity than female players. A higher acceleration in men was accompanied by shorter gliding time, longer step length, and higher step frequency. When skating at maximal speed, male players had a longer step length and gliding time and length. The sub-group analysis revealed that step frequency did not correlate with skating velocity, acceleration, or maximal speed phases. On the other hand, glide and step lengths significantly correlated with skating velocity in both phases (r ≥ 0.60). Conclusions: In general, for faster skating in bandy, it is generally better to prioritise glide and step length than stride frequency. Hence, players should be encouraged to stay low and have more knee flexion to enable a longer extension length and, therefore, a longer path and more horizontal direction of applied force to enhance their acceleration ability. Full article

A brain aneurysm is a structural deterioration of the arterial wall in the brain, resulting in the formation of a bulge in or ballooning of a blood vessel. Around 3–5% of the global population is affected by brain aneurysms, wherein only a small fraction results in rupture. Although an unruptured aneurysm is typically asymptomatic and not immediately life threatening, it poses a potential risk of rupture, which can lead to severe health complications or mortality. Therefore, it is crucial to detect and treat aneurysms during the unruptured phase. Moreover, a comprehensive understanding of the flow dynamics within the aneurysm and its parent artery is essential for accurate diagnosis and the prevention of aneurysm recurrence. While prior reviews have focused on computational fluid dynamics (CFD) studies on brain aneurysms, particularly patient-specific models from studies conducted over a decade ago, a more recent review is necessary. Additionally, reviewing various studies on the fluid dynamic behavior of treated aneurysms is crucial. Thus, the advancements in both experimental and computational studies on brain aneurysms must be explored to better understand their underlying fluid flow mechanisms and to develop robust treatment strategies. This review aims to summarize the different types of brain aneurysms, the screening and treatment processes, the key hemodynamic factors, and the fluid dynamic characteristics observed in aneurysms before and after treatment. Full article

Background: CrossFit^® aims to be equitable between both males and female athletes, supporting equal representation and equal prize money at international events. However, to date, limited information is known on CrossFit^® athletes’ performance in the countermovement jump (CMJ), countermovement rebound jump (CMR-J), and isometric mid-thigh pull (IMTP) when assessed using force plates, and if there are any differences between sexes. Therefore, the purpose of the present study was to observe whether any sex-based differences and relationships exist between performance within these assessments. Methods: A total of CrossFit athletes (43 male = 32.8 ± 9.0 years; height 1.78 ± 0.06 m; mass = 92.4 ± 10.6 kg; and 31 female = 31.0 ± 7.6 years, height = 1.64 ± 0.05 m; mass = 68.8 ± 6.0 kg) completed three trials of CMJ, CMR-J and IMTP using portable dual-system force-plate sampling at 1000 Hz. Results: Moderate–large relationships were observed between CMJ, CMR-J and IMTP outcome measures (r = 0.396–0.809, p < 0.001). Males demonstrated small to moderately greater performance outcomes than females for CMJ height (males = 0.35 ± 0.08 m; females 0.30 ± 0.06 m, d = 0.73), CMR-J height (males = 0.32 ± 0.08 m; females = 0.30 ± 0.06 m, d = 0.39) and IMTP peak net force (males = 30.62 ± 10.01 N·kg⁻¹; females = 27.49 ± 6.44 N·kg⁻¹, d = 0.29). Conclusions: Maximal relative strength in CrossFit^® athletes should be seen as imperative in both male and female athletes due to the meaningful relationship in ballistic and plyometric ability. Moreover, previous relationships with CrossFit^® performance and the injury risk reduction benefits of improving strength provide further support. The descriptive data presented could be used by CrossFit^® coaches to assess and compare the current performance of their own athletes in a battery of tests examining CMJ, CMR-J and IMTP, while also facilitating decisions upon prescription within training and competition. Full article

(1) Background: Plantar heel pain (PHP), a common overuse foot injury, significantly impacts runners. While the mechanical role of the plantar fascia during gait is established, its effect on foot function during running, particularly foot joint coupling, remains unclear. This study investigated foot joint coupling during running in runners with and without PHP using statistical parametric mapping (SPM). (2) Methods: Thirteen uninjured runners (seven m, six f; age = 30.5 ± 5.9 years; BMI = 23.5 ± 3.0 kg/m²) and thirteen runners with PHP (six m, seven f; age = 29.0 ± 8.0 years; BMI = 23.1 ± 2.0 kg/m²) performed running trials at 4.0 m/s. A seven-segment foot model that defined six functional articulations (rearfoot, medial and lateral midfoot, medial and lateral forefoot, first metatarsophalangeal) was used to quantify foot kinematics, vector coding was used to calculate joint coupling between adjacent foot segments, and SPM was used to analyze joint stance phase coupling angles. (3) Results: There were statistically significant differences in rearfoot frontal plane–medial midfoot frontal plane joint coupling between runners with and without PHP from 69 to 70% stance phase (mean difference = 39.41°) and at 76% stance (mean difference = 47.89°). The differences were indicative of greater medial midfoot eversion rotation relative to rearfoot complex inversion in the PHP group. (4) Conclusions: The difference in the rearfoot complex and medial midfoot frontal plane coupling occurred during the propulsion phase of the running stance when the foot should be transitioning to a more supinated position, which may reflect compromised supination due to plantar fascia degeneration. Full article

This study investigated kinetic and physiological load characteristics of Self-Manual Resistance Training (SMRT) lat pulldown. SMRT lat pulldown is a training method in which practitioner generates resistance manually using their own muscular force by gripping a towel with both hands and pulling it outward in a horizontal direction. We analyzed shoulder and elbow joint moments in frontal plane (2D) and muscle activity levels of latissimus dorsi (LD), posterior deltoid (PD), biceps brachii (BB), and triceps brachii (TB) during 10 maximal-effort repetitions of SMRT lat pulldown in 11 resistance-trained men. For comparison, we also measured muscle activity levels during a machine lat pulldown for 10 reps at 75% 1 RM load in same participants. Peak shoulder adduction and elbow extension moments during SMRT lat pulldown were both approximately 70% MVC. Mean rectified EMG of LD was significantly greater during machine lat pulldown than SMRT lat pulldown, whereas that of PD was significantly greater during SMRT than machine version. Mean rectified EMG of TB was high during SMRT, and that of BB was high in machine version. SMRT lat pulldown appears to produce relatively large shoulder adduction and elbow extension moments, increasing PD and TB activation and limiting LD activation. Full article

As powerful actions commonly proceed goal scoring opportunities within soccer, enhancing powerful actions could be essential to optimize performance. There is a large body of evidence supporting the positive associations between maximal isometric mid-thigh pull force-generating qualities and jump performance. Objectives: The purpose of this study was to determine if relative maximal isometric force production can discriminate between higher- and lower-performing jumpers among professional and semi-professional soccer players. As such, it was hypothesized that stronger players would have a greater jump performance than weaker players. Methods: An observational cross-sectional research design was used to assess ballistic and isometric force production of the lower limbs across players from four professional and semi-professional soccer clubs during the pre-season period. Seventy-six professional male lower-league soccer players (mass: 82.5 ± 8.2 kg; height: 1.80 ± 0.07 m; age: 25.8 ± 4.3 years) performed three trials of the countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) using force plates. Players were categorized as strong and weak using the group’s average IMTP relative peak force (33.41 N/kg). A series of one-way Bayesian independent t-tests were performed to determine the difference between strong and weak groups. Results: A large magnitude of difference was observed between strong and weak players for relative peak force (d [95% CI] = 2.53 [2.017–∞]), with strong evidence supporting the hypothesis (BF₁₀ = 2.698 × 10⁺¹⁴). There was moderate evidence to support the hypothesis that strong players (n = 37) had a greater modified reactive strength index (mRSI) and relative average braking force in comparison to weaker players (n = 39). All other evidence was weak, with trivial-to-small differences (d = 0.10–0.42) for jump height, jump momentum, propulsive force, force at minimum displacement, time to take off, and countermovement depth. Conclusions: Maximal relative strength has implications on jump performance, albeit not on the jump outcome. Stronger players performed the CMJ more efficiently when observing the mRSI, with a shorter time to take off, while producing greater average relative forces during the braking phase. This could have potential implications in the sporting environment when performing jumping tasks, where they can achieve a similar outcome over a shorter duration. Full article

Background: Gravity profoundly influences human locomotion. Studies examining the effects of hyper-gravity on gait have largely relied on added external mass, potentially confounding results with changes in inertia and center of mass. This study attempted to isolate the effects of increased gravitational load on kinematics and electromyography during walking at several different levels of load. Methods: Fifteen healthy adults were exposed to simulated gravitational loads ranging from 100% to 130% of body weight using a novel harness and spring-based system that increased weight without the addition of external mass and without altering limb inertia. Participants walked on a treadmill at a self-selected speed through incremental loading and unloading. Lower limb kinematics and electromyography data were recorded. Traditional measures of gait, as well as more dynamical measures, including angle–angle analysis and phase portraits, were examined. Results: Data demonstrated that a 130% load is sufficient to induce kinematic changes at the hip and knee; however, these changes become significant only during the transition from 130% to lower load levels. Ankle kinematics and electromyography appeared to be unaffected. Conclusions: These findings suggest that the presence of external mass and alterations in limb inertias should be considered seriously as independent variables in future loading studies, and that weight and mass may need to be considered as separate effectors during locomotion. This study also found that the act of loading and unloading elicit distinct responses in the joints of the lower extremities, as well as that it may induce an adaptative after-effect. Full article