GASTROCNEMIUS TENDON LENGTH AND WALKING ECONOMY IN BLACK AND WHITE WOMEN

Abstract

Findings from comparative animal biology indicate that the energy savings due to elasticity of tendons may translate into greater economy of walking when muscles of locomotion have longer tendons. PURPOSE The purpose of this study was to determine wether gastrocemius tendon length is related to walking economy (defined as 1/ml O2/kg/min) in humans. An additional purpose was to compare walking economy and gastrocnemius tendon length between Black and White women. It was hypothesized that tendon length would be related to walking economy, and that Black women would have longer gastrocnemius tendon lengths and, hence, be more economical walkers. METHODS We evaluated walking economy at 4.8 km/hr at 0% and 2.5% grade in 14 Black and 19 White premenopausal women. Plantar flexor muscle metabolic economy (force/ATP) was also evaluated using 31 phosphate magnetic resonance spectroscopy (31P-MRS). Gastrocnemius tendon length was measured using magnetic resonance imaging. RESULTS Tendon length was only related to level walking economy (0.38, p = 0.03). Black women walked on the flat more economically (Black 0.126 and White 0.110, 1/ml O2/kg/min, p = 0.04) and had longer gastrocnemius tendon lengths than White women (Black 17.9 and White 15.6 cm, p = 0.005). No significant racial differences were observed while walking up a 2.5% grade or in 31P-MRS determined plantar flexor muscle metabolic economy. CONCLUSION These data show that gastrocnemius tendon length is related to level walking economy but not grade walking or isometric gastrocnemius plantar flexion metabolic economy. In addition, Black women have longer gastrocnemius tendons than White women and are more economical during level waling. Support: NIH R01 DK 49779 & NIH R01 DK51684