ECSS Paris 2023: OP-BM11
INTRODUCTION: In running, hip extensors such as the gluteus maximus (Gmax) and the hamstrings contribute significantly to forward acceleration of the body, particularly at high running speeds (1). Among the hamstrings, hypertrophy after sprint-specific training is more pronounced in the semitendinosus (ST) and biceps femoris long head (BFlh), than in the semimembranosus (SM) (2). This can be partly explained by the different architecture of these muscles (3). However, the effect of non-uniform muscle hypertrophy on hip extensor torque has not been investigated. In addition, non-uniform distribution of muscle activation between the hip extensors may also contribute to the non-uniform adaptations to long-term training. In this study we hypothesized that the torque-angular velocity relationship would differ between power and strength-trained athletes. We also hypothesized that the excitation of Gmax, ST, and BFlh would increase with increasing hip extension angular velocity on a dynamometer, which was not expected in SM. METHODS: Thirteen competitive track and field athletes from sprint-based disciplines and 14 matched strength-trained controls participated in this study. Hip extension torque and electromyography (EMG) activity of the Gmax, ST, BFlh, and SM were recorded during maximal intensity isometric (50 deg hip flexion) and concentric contractions at 60, 120, 180, and 240 deg/s angular velocity when the dynamometer range of motion was 70 deg to -20 deg (neutral position = 0 deg). The knee was fixed at 40 degrees of flexion. The hip joint angle was measured using 3-D motion analysis to match the hip range of motion between individuals. Torque and EMG activity for each muscle and their interactions were compared between groups and contraction velocities. RESULTS: There was no difference in isometric torque between the groups, but concentric torque was higher in the sprinting group than in the strength-trained group, especially at high angular velocities (p<0.05). In the strength-trained group, EMG activity did not increase in any of the muscles with increasing contraction velocity. In the sprinting group, EMG activity increased in all muscles with increasing contraction velocity (p<0.01). However, there was a significant muscle*velocity interaction, with an increase in hamstring EMG activity being most pronounced in the BFlh and ST as compared to a smaller increase in the SM. CONCLUSION: Our results suggest that the velocity-dependent neuromuscular excitation pattern of the hamstrings is unique to sprint-trained athletes, which may explain why ST and BFlh show preferential hypertrophy after sprint-specific training. It appears that the ability of hip extensors to produce torque at high running speeds is a combined result of superior muscle volume and superior muscle excitation of muscles with a relatively low pennation angle. REFERENCES: 1) Pandy et al. Scand J Med Sci Sports 2021 2) Kawama et al. Eur J Sports Sci 2024 3) Ward et al. Clin Orthop Relat Res 2009 CONTACT: hegyi.andras@tf.hu
Read CV Andras HegyiECSS Paris 2023: OP-BM11
INTRODUCTION: Plantar flexor muscles exhibit inter-individual variations in muscle bulging patterns during muscle contraction (1). Muscle shape affects its force production capacity, and different shapes may benefit the specific requirements of the sport. Sprint running requires higher propulsive forces, while distance running requires efficient muscle function over prolonged durations. While plantar flexor muscle volume has already been compared between sprinters and distance runners, these measures lack sensitivity to regional shape differences. This study aimed to compare the shape of plantar flexor muscles between sprinters and distance runners. METHODS: Fourteen sprinters (IAAF score: 983 ± 110, 5 females) and fifteen distance runners (IAAF score: 953 ± 116, 5 females) were recruited. The 3-D muscle volume of the plantar flexor muscles was reconstructed by scanning the right leg using T1-weighted magnetic resonance imaging. Muscle segmentation was performed manually to establish muscle boundaries and to generate the 3-D mesh of the muscles. Statistical shape modeling (2) was used to compare the differences in the group average shape of the medial (MG) and lateral gastrocnemius (LG) and the four compartments of the soleus for male and female athletes. RESULTS: MG muscle shape was similar in the male distance and sprint runners, but female sprint runners had significantly larger proximal and distal MG (36.44% of the total vertices) compared to female distance runners. LG was more expanded across the length of the muscle on both the dorsal and frontal sides, with 30% of the total vertices showing this expansion in male sprinters compared to male distance runners. Similarly, female sprint runners had larger LG at the proximal and distal ends of the muscle (14.36% of the total vertices). We observed statistical differences in the average shape of the four compartments of the soleus at a few minor locations in both male and female runners. CONCLUSION: This study provides novel insights into the differences in the plantar flexor muscles’ shape between elite sprint and distance runners. Future research should investigate the functional implications of these differences and their relationship to performance. We further encourage longitudinal studies to understand training-induced changes in muscle shape. REFERENCES: 1) Kelp et al., J Exp. Biol. 2024 2) Bolsterlee, J. Appl. Physiol. 2022
Read CV Bálint KovácsECSS Paris 2023: OP-BM11
INTRODUCTION: Plyometric and ballistic exercises incorporated into warm-up protocols have been reported to enhance sprint performance [1,2]. However, previous research often used these terms interchangeably while implementing exercises that combined both concepts [1,3,4]. These two concepts stimulate distinct neuromuscular adaptation mechanisms such as stretch reflexes in plyometric versus motor unit recruitment in ballistic exercises. Given the debated implications of isolating these concepts (e.g., non-ballistic plyometric exercises) [5], understanding their individual effects and contributions to sprint performance is important. This study aimed to investigate the acute effects of distinct plyometric and ballistic warm-ups in sprinting. METHODS: Fifteen collegiate sprinters (height: 1.74±0.05 m, weight: 67.7±4.03 kg, personal best back squat: 130.0±21.7 kg) completed four sessions in randomized order, separated by 24 hours. Each session included 5 minutes of low-intensity jogging, followed by one of four protocols (traditional as control, plyometric, ballistic, or mixed plyometric-ballistic) and two preparatory sprints before a single 40-m sprint for data collection. Kinetic and spatiotemporal data as well as split times at 10, 20, 30, and 40 m were obtained via 54 force plates embedded in a tartan track. Repeated-measures one-way ANOVA examined effects of warm-ups, with a significance level of α=.05. RESULTS: Of the 13 tests conducted, only one revealed a significant effect of warm-ups: step length at 40 m (p<.05, pη2=.21), where step length was greater in the plyometric (2.19±0.14 m) than in the mixed protocol (2.11±0.14 m) in Bonferroni-corrected pairwise comparison (p<.05). No effects were found for maximum horizontal force and power output (p=.35–.46, pη2=.06–.07), contact and flight times at the start and 40 m, step length at the start (p=.10–.85, pη2=.02–.14), and any split times (p=.38–.79, pη2=.03–.07). Other pairwise comparisons also showed no significant differences (p=.07–1). CONCLUSION: The findings suggest no clear superiority of plyometric and ballistic over traditional warm-ups. The sole statistically significant result (step length at 40 m) may reflect a type I error rather than practical relevance. Contrary to previous reports [1-4], these results question whether plyometric and ballistic warm-ups provide substantial benefits over traditional methods. The protocols employed in previous studies [1,3,4] suggest that previously observed advantages might be due to suboptimal control protocols that did not adhere to best practices. Further research is necessary to validate or refute the benefits of plyometric and ballistic warm-ups compared to well-designed traditional protocols. REFERENCES: 1) Creekmur et al., J Sports Med Phys Fitness, 2017 2) Maloney et al., Sports Med, 2014 3) Gil et al., Int J Environ Res Public Health, 2019 4) Turner et al., J Strength Cond Res, 2015 5) Frost et al., Sports Biomech, 2008
Read CV Wei Hsuan ChuangECSS Paris 2023: OP-BM11