Author(s): KOVÁCS, B., KÓBOR, I., GYEBNÁR, G., HORTOBÁGYI, T., Institution: HUNGARIAN UNIVERSITY OF SPORT SCIENCE, Country: HUNGARY, Abstract-ID: 521

INTRODUCTION:
Plantar flexor muscles generate the most propulsion during running. The architecture of the plantarflexors determines the ability to generate force, hence muscle architecture could be related to running performance. The dynamics of mechanical power generation differ substantially between the sprinting and distance running. This distinct ankle power generation during running is expected to produce event-specific adaptations in the architecture of the constituent muscles of the ankle plantarflexors, i.e., in the monoarticular soleus and the biarticular medial and lateral gastrocnemius. Based on the extant data, we hypothesize that sprinters compared with distance runners have longer fascicles and a large physiological cross-sectional area (PCSA) in the gastrocnemii muscles. We expect that distance runners compared with sprinters would have shorter soleus fascicles and larger soleus PCSA.
METHODS:
In this study, we recruited 14 sprinters (WA score: 1003± 63; 9 males) and 15 distance runners (WA score: 960±104; 10 males). 3D muscle architecture of the plantar flexor muscles was reconstructed by scanning the right leg using T1 and DTI-MRI sequences. T1 scans were segmented then the 3D mesh of the muscles was generated. DTI tractography was used to reconstruct the architecture of the plantar flexor muscles. Muscle volume, average fascicle length, pennation angle, and PCSA were estimated for each of the medial and lateral gastrocnemii as well as for four compartments of the soleus muscle. To comprehensively compare the 3D architecture of the plantarflexors muscles, we used statistical shape modeling with bootstrapping to assess statistical significance. The force-velocity power profile of the muscles was calculated using the Hill equation.
RESULTS:
Sprinters vs. distance runners had significantly shorter medial gastrocnemius fascicle length (7.13 ±SD 1.81 vs. 8.05 ±1.36 cm). Lateral gastrocnemius (7.09 ± 1.29 vs. 7.29 ±1.41 cm) and soleus (3.79 ±1.06 vs. 3.44 ±0.93 cm) fascicle lengths did not differ between the two groups of runners. Sprinters compared with distance runners had modestly smaller pennation angles in most muscles and both sexes. The spatial distribution of the differences in pennation angle was heterogeneous across nodes. PCSA of the medial gastrocnemius, lateral gastrocnemius, and soleus was 19.9% ±9.2 (p = 0.075), 10.8% ±8.4 (p = 0.19), and 19.3% ±13.9 (p = 0.17) greater, respectively, in sprinters compared with distance runners. Consequently, total plantarflexor PCSA was 8.4 cm² (5% ±15.1) greater in sprinters than distance runners (p = 0.61).
CONCLUSION:
Sprinters compared with distance runners had larger gastrocnemii but smaller soleus PCSA, with greater theoretical mechanical output. The simple muscle model using the architectural data as input reflects real-life differences between the two groups of runners. However, none of the architectural variables predicted running performance.