17th Annual ECSS-Congress, Bruges 2012

Abstract details

Abstract-ID: 991
Session: [MO-BN01] Motor learning & Biomechanics
Lecture room: High Live 4
Date & time: 24.06.2015 / -
Authors: Nishida, K.1, Hagio, S.1,2, Kibushi, B.1, Moritani, T.1, Kouzaki, M.1
Institution: 1: Kyoto Univ. (Kyoto, Japan), 2: JSPS (Tokyo, Japan)
Department: Graduate School of Human and Environmental Studies
Country: Japan
Abstract text Introduction Runners fall into two broad categories based on foot strike patterns: a fore-foot strike (FFS), in which the ball of the foot lands before the heel comes down; and a rear-foot strike (RFS), in which the heel lands first. The differences between FFS and RFS have been only studied in terms of ground reaction forces (Lieberman et al., 2010), knee loading (Kulmala et al., 2013), and running economy (Gruber et al., 2013). The aim of this study was to compare FFS with RFS based on muscle synergies (Hagio et al., 2015). Methods Six healthy male subjects ran on a treadmill at different speeds (5, 7, 9, 12, and 15 km/h). At each speed, subjects were asked to run both in FFS and RFS. Surface electromyogram (EMG) activity was recorded from 12 muscles on both sides of the trunk and lower body. Muscle synergies were extracted from an EMG data matrix using non-negative matrix factorization (Lee and Seung, 1999). Results Both in FFS and RFS, six synergies (Syn1-6) were extracted. The general characteristics of the synergies were similar between FFS and RFS. However, in all subjects, Syn3 and Syn6, which were activated just before touchdown, recruited tibialis anterior (TA) much more in RFS than in FFS. In a subject, Syn1 and Syn4, which were activated around touchdown, recruited triceps surae (TS) slightly more in FFS than in RFS. Moreover, in two subjects, Syn2 and Syn5, which mainly recruited TS and were activated during stance, showed bi-modal activation patterns in FFS while mono-modal in RFS, so that they were also activated around touchdown in FFS. Discussion The difference of TA seems to come from the necessity of the dorsal flexion of ankle joint just before touchdown in RFS. On the other hand, the reason of the differences of TS and activation patterns seems to be because the activity of TS absorbed touchdown impact in FFS. In conclusion, the results suggest that the central nervous system controls running rhythmically activating six muscle synergies, switches from FFS to RFS changing the weighting in specific synergies, and adjusts the absorption of touchdown impact changing the weightings or the activation patterns. References Gruber AH, Umberger BR, Braun B, Hamill J. (2013). J Appl Physiol, 115, 194-201 Hagio S, Fukuda M, Kouzaki M. (2015). Front Hum Neurosci, 9:48. Kulmala JP, Avela J, Pasanen K, Parkkari J. (2013). Med Sci Sports Exerc, 45(12), 2306-2313. Lee DD, Seung HS. (1999). Nature, 401, 788-791. Lieberman DE, Venkadesan M, Werbel WA, Daoud AI, D’Andrea S, Davis IS, Mang’Eni RO, Pitsiladis Y. (2010). Nature, 463, 531-535. Contact higashi_kyoto@me.com
Topic: Neuromuscular Physiology
Keyword I: running
Keyword II: foot strike patterns
Keyword III: muscle synergies