Changes in sarcomere lengths of the human vastus lateralis muscle with knee flexion measured using in vivo microendoscopy

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• 作者：Xuefeng Chen^a ; Gabriel N. Sanchez^a ; ^b ; Mark J. Schnitzer^c ; ^d ; ^e ; Scott L. Delp^a ; ^b ; ^{delp@stanford.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Muscle ; Sarcomere ; Strength ; Knee ; Microendoscopy
• 刊名：Journal of Biomechanics
• 出版年：2016
• 出版时间：6 September 2016
• 年：2016
• 卷：49
• 期：13
• 页码：2989-2994
• 全文大小：1152 K

文摘

Sarcomeres are the basic contractile units of muscle, and their lengths influence muscle force-generating capacity. Despite their importance, in vivo sarcomere lengths remain unknown for many human muscles. Second harmonic generation (SHG) microendoscopy is a minimally invasive technique for imaging sarcomeres in vivo and measuring their lengths. In this study, we used SHG microendoscopy to visualize sarcomeres of the human vastus lateralis, a large knee extensor muscle important for mobility, to examine how sarcomere lengths change with knee flexion and thus affect the muscle׳s force-generating capacity. We acquired in vivo sarcomere images of several muscle fibers of the resting vastus lateralis in six healthy individuals. Mean sarcomere lengths increased (p=0.031) from 2.84±0.16 μm at 50° of knee flexion to 3.17±0.13 μm at 110° of knee flexion. The standard deviation of sarcomere lengths among different fibers within a muscle was 0.21±0.09 μm. Our results suggest that the sarcomeres of the resting vastus lateralis at 50° of knee flexion are near optimal length. At a knee flexion angle of 110° the resting sarcomeres of vastus lateralis are longer than optimal length. These results show a smaller sarcomere length change and greater conservation of force-generating capacity with knee flexion than estimated in previous studies.