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Gastrocnemius muscle fascicle behavior during stair negotiation in humans

¹Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager Campus, United Kingdom; and ²Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands

Submitted 24 March 2006 ; accepted in final form 14 December 2006

The aim of the present study was to establish the behavior of human medial gastrocnemius (GM) muscle fascicles during stair negotiation. Ten healthy male subjects performed normal stair ascent and descent at their own comfortable speed on a standard-dimension four-step staircase with embedded force platforms in each step. Kinematic, kinetic, and electromyographic data of the lower limbs were collected. Real-time ultrasound scanning was used to determine GM muscle fascicle length changes. Musculotendon complex (MTC) length changes were estimated from ankle and knee joint kinematics. The GM muscle was mainly active during the push-off phase in stair ascent, and the muscle fascicles contracted nearly isometrically. The GM muscle was mainly active during the touch-down phase of stair descent where the MTC was lengthened; however, the GM muscle fascicles shortened by 7 mm. These findings show that the behavior and function of GM muscle fascicles in stair negotiation is different from that expected on the basis of length changes of the MTC as derived from joint kinematics.

biomechanics; muscle mechanics; ultrasound; musculotendon complex; tendon

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				M. Spanjaard, N. D. Reeves, J. H. van Dieen, V. Baltzopoulos, and C. N. Maganaris Lower-limb biomechanics during stair descent: influence of step-height and body mass J. Exp. Biol., May 1, 2008; 211(9): 1368 - 1375. [Abstract] [Full Text] [PDF]