Three distinctive activities of human triceps surae muscle during the stance phase in treadmill walking and running.
Activity of human triceps surae muscle (TS) during locomotion was investigated in relation to the muscle shortening and lengthening contractions. Length changes in the TS were presumed from its girth recorded using a mercury-in-silastic gauge wrapped around the muscle belly. The muscle girth during the stance phase resulted in three peaks corresponding to the actions of heel contact, weight support and toe kick. These peak heights were apparently larger than the girth level in the perpendicular standing posture. Three girth increases in running appeared in the process of ankle dorsiflexion. During walking, girth increases on weight support and toe kick were seen in the same phase. The TS through the stance phase is considered to always contract into a shortening state less than the muscle length in the perpendicular standing posture. These muscle activities are probably imposed to resist the muscle stretching. Therefore, it was suggested that the TS contracts eccentrically, with no lengthening contraction.
Nagami
K
K
Department of Physiology, Tokai University School of Medicine, Kanagawa, Japan.
Fujise
T
T
Uchiyama
S
S
D000328:Adult; D001132:Arm; D004576:Electromyography; D005080:Exercise Test; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000502:physiology*; D012420:Running; D016138:Walking