Abstract
The main function of skeletal muscles is to generate force. The force developed by myofiber contraction is transmitted to the tendon. There are two pathways of force transmission from myofibers to tendons: longitudinal transmission that depends on tension elicited via the myotendinous junction and lateral transmission that depends on shear elicited via the interface between the myofiber surface and surrounding connective tissue. Experiments using animal muscle and mathematical models indicated that lateral transmission is the dominant pathway in muscle force transmission. Studies using rat muscle showed that the efficiency of lateral force transmission declines with age. Here, the lateral transmission of force was measured using the extensor digitorum longus muscle from young and old mice. Dependence on longitudinal transmission increased in the old muscle, and there was a trend for lower efficiency of lateral force transmission in the old muscle compared to the young muscle. There was a noticeable increase in the connective tissue volume in the old muscle; however, there was no significant change in the expression of dystrophin, a critical molecule for the link between the myofiber cytoskeleton and extracellular matrix. This study demonstrates the measurement of lateral force transmission in mouse muscles and that alteration in force transmission property may underlie age-related muscle weakness.
Highlights
IntroductionThe primary function of skeletal muscles is to generate force by contraction
Lateral force transmission can be examined by measuring the maximum tetanic force in each step during a series of tenotomy and myotomy of the extensor digitorum longus (EDL) muscle [4]
The lateral force transmission of the mouse EDL muscle was measured by applying a series of tenotomy and myotomy steps, a technique used in rat muscles [4]
Summary
The primary function of skeletal muscles is to generate force by contraction. Force is originally produced by actin–myosin crossbridge cycling within myofibers. The force exerted by the myofiber is transmitted to the tendon to pull the bone. Force generation and transmission are essential properties of skeletal muscles and are required for exercise, physical activity, and postural maintenance. Two pathways are involved in force transmission from myofibers to tendons [1]. A widely accepted pathway is that force developed in myofibers is transmitted directly to the tendon by tension elicited via the myotendinous junction (MTJ). This pathway is termed longitudinal force transmission
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