Muscle and Tendon Relations in Humans
To clarify the mechanisms of power enhancement during counter-movement exercise, in vivo muscle fibre behavior during plantar flexion exercise was estimated by real time ultrasonography. Six healthy male subjects were requested to perform ankle plantar flexion exercise with counter-movement (CM, plantar flexion preceded by dorsiflexion) and without counter-movement (noCM, plantar flexion only) on a specially designed dynamometer. In CM, in the dorsiflexion phase, muscle fascicle length was initially lengthened, following which its length remained unchanged while the whole muscle-tendon unit was still lengthened, and decreased in the plantar flexion phase. In noCM, fascicle length decreased throughout the movement and it was longer at the onset of movement than in CM. During dorsiflexion phase in CM, muscle fascicles were not actively lengthened, but contracted isometrically at near optimum length of fibre; thus the increase in muscle-tendon unit length was taken up by elongation of the tendinous tissues. These results demonstrate that power enhancement during CM is due to higher force production by isometric contraction at optimal fibre length.
KeywordsJoint Angle Isometric Contraction Plantar Flexion Ankle Angle Fascicle Length
Unable to display preview. Download preview PDF.
- Fukunaga, T., Ichinose, Y., Ito, M., Kawakami, Y. and Fukashiro, S., 1997, Determination of fascicle length and pennation in a contracting human muscle in vivoJournal Applied Physiology82, 354–358.Google Scholar
- Hoffer, J. A., Acputi, A. A., Pose, I. E., and Griffiths, R. I., 1989, Roles of muscle activity and load on the relationship between muscle spindle length and whole muscle length in the freely walking cat, in:Progress in Brain ResearchAllum, J. H. J. and Hulliger, M., eds., pp. 80, 75–85.Google Scholar
- Huijing, P. A., 1992, Elastic potential of muscle, in:Strength and Power in SportKomi, P.V., ed., pp. 151–168.Google Scholar
- Kawakami, Y., Kumagai, K., Huijing, P. A., Hijikata, T. and Fukuriaga, T., 2000, The length-force characteristics of human gastrocnemius and soleus muscles in vivo, in:Skeletal Muscle MechanicsHerzog, W., ed., pp. 327–341.Google Scholar
- Komi, P. V., 1991, Stretch shortening cycle, in:Strength and Power in SportKomi, P. V., ed., pp. 169–179.Google Scholar