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This Article Full Text Free Full Text (PDF) Free Supplemental Video All Versions of this Article: 104/5/1320    most recent 01069.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Finni, T. Articles by Cheng, S. Search for Related Content PubMed PubMed Citation Articles by Finni, T. Articles by Cheng, S.

Mechanical behavior of the quadriceps femoris muscle tendon unit during low-load contractions

¹Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland; ²Department of Radiology, University of California at San Diego School of Medicine, San Diego, California; ³Nomir Oy, Tampere, Finland; and ⁴Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland

Submitted 8 October 2007 ; accepted in final form 10 March 2008

We examined the relationships between morphology and muscle-tendon dynamics of the quadriceps femoris muscle of 11 men using velocity-encoded phase-contrast magnetic resonance imaging (MRI). Thigh muscle electromyography and joint range of motion were first measured outside the MRI scanner during knee extension-flexion tasks that were performed at a rate of 40 times/min with elastic bands providing peak resistance of 5.2 kp (SD 0.4) to the extension. The same movement was repeated inside the MRI scanner bore where tissue velocities and muscle morphology were recorded. The average displacement in the proximal and distal halves of the rectus femoris and vastus intermedius aponeuroses was different (P = 0.049), reflecting shortening (1.6%), but the tensile strain along the length of the aponeuroses was uniform. The aponeurosis behavior varied among individuals, and these individual patterns were best explained by the differences in relative cross-sectional area of rectus femoris to vastus muscles (r = 0.71, P = 0.014). During dynamic contraction, considerable deformation of muscles in the axial plane caused an anatomic measure such as muscle thickness to change differently (decrease or increase) in different sites of measurement. For example, when analyzed from the axial images, the vastus lateralis thickness did not change (P = 0.946) in the frontal plane through femur but increased in a 45° oblique plane between the frontal and sagittal planes (P = 0.004). The present observations of the heterogeneity and individual behavior emphasize the fact that single-point measurements do not always reflect the overall behavior of muscle-tendon unit.

muscle thickness; architecture; strain; aponeurosis