Forefoot running requires shorter gastrocnemius fascicle length than rearfoot running

ABSTRACT

This study aimed to investigate the influence of foot strike patterns on the behaviour of the triceps surae muscle-tendon unit, including the Achilles tendon whose length nearly corresponds to force of the triceps surae, and the medial gastrocnemius muscle (MG) during running. Seven male volunteers ran with forefoot and rearfoot strikes at 10, 14 and 18 km h⁻¹ on a treadmill. The MG fascicle length was measured using ultrasonography. The in vivo length of the curved Achilles tendon was quantified by combining ultrasonography with optical motion capture of reflective markers on the right lower limb and an ultrasound probe. The forefoot strike resulted in a significantly shorter MG fascicle length at the initial contact, at Achilles tendon peak elongation, and at toe-off, than the rearfoot strike. The Achilles tendon length at initial contact was greater during the forefoot strike than during the rearfoot strike at 18 km h⁻¹, while its peak elongation was not significantly different during forefoot and rearfoot running. These results indicate that the MG, with a shorter length during forefoot running, manages to address demands for a similar peak force of the triceps surae than during rearfoot running.

KEYWORDS:

• Analytical calculation
• aponeurosis
• force–length relationship
• pennate muscle
• plantar flexor
• triceps surae

Acknowledgments

The authors are grateful to Hitachi-Aloka Medical, Ltd., for enabling this study to be undertaken by lending the ultrasound apparatus. The technical assistance of Mr Shimpei Kubo and students is also gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the corresponding author, R. K., upon reasonable request.

Supplementary material

The supplemental data for this article can be accessed here.

Additional information

Funding

This work was funded by JSPS KAKENHI 16K01740 (to R.K.).