TY  - JOUR
A1  - Werkhausen, Amelie
A1  - Willwacher, Steffen
A1  - Albracht, Kirsten
T1  - Medial gastrocnemius muscle fascicles shorten throughout stance during sprint acceleration
JF  - Scandinavian Journal of Medicine & Science in Sports
N2  - The compliant nature of distal limb muscle-tendon units is traditionally considered suboptimal in explosive movements when positive joint work is required. However, during accelerative running, ankle joint net mechanical work is positive. Therefore, this study aims to investigate how plantar flexor muscle-tendon behavior is modulated during fast accelerations. Eleven female sprinters performed maximum sprint accelerations from starting blocks, while gastrocnemius muscle fascicle lengths were estimated using ultrasonography. We combined motion analysis and ground reaction force measurements to assess lower limb joint kinematics and kinetics, and to estimate gastrocnemius muscle-tendon unit length during the first two acceleration steps. Outcome variables were resampled to the stance phase and averaged across three to five trials. Relevant scalars were extracted and analyzed using one-sample and two-sample t-tests, and vector trajectories were compared using statistical parametric mapping. We found that an uncoupling of muscle fascicle behavior from muscle-tendon unit behavior is effectively used to produce net positive mechanical work at the joint during maximum sprint acceleration. Muscle fascicles shortened throughout the first and second steps, while shortening occurred earlier during the first step, where negative joint work was lower compared with the second step. Elastic strain energy may be stored during dorsiflexion after touchdown since fascicles did not lengthen at the same time to dissipate energy. Thus, net positive work generation is accommodated by the reuse of elastic strain energy along with positive gastrocnemius fascicle work. Our results show a mechanism of how muscles with high in-series compliance can contribute to net positive joint work.
KW  - locomotion
KW  - muscle mechanics
KW  - running
KW  - sprint start
KW  - ultrasonography
Y1  - 2021
U6  - http://dx.doi.org/10.1111/sms.13956
SN  - 0905-7188 (Druckausgabe)
SN  - 1600-0838 (Onlineausgabe)
VL  - 31
IS  - 7
SP  - 1471
EP  - 1480
PB  - Wiley-Blackwell
CY  - Oxford
ER  - 
TY  - CHAP
A1  - Braunstein, Bjoern
A1  - Goldmann, Jan-Peter
A1  - Albracht, Kirsten
A1  - Sanno, Maximilian
A1  - Willwacher, Steffen
A1  - Heinrich, Kai
A1  - Herrmann, Volker
A1  - Brüggemann, Gert-Peter
T1  - Joint specific contribution of mechanical power and work during acceleration and top speed in elite sprinters
T2  - 31 International Conference on Biomechanics in Sports, Taipei, Taiwan, July 07 - July 22, 2013
Y1  - 2013
SN  - 1999-4168
ER  -