Skeletal muscle tissue in movement and health: positives and negatives

Abstract

The history of muscle physiology is a wonderful lesson in 'the scientific method'; our functional hypotheses have been limited by our ability to decipher (observe) muscle structure. The simplistic understanding of how muscles work made a large leap with the remarkable insights of A. V. Hill, who related muscle force and power to shortening velocity and energy use. However, Hill's perspective was largely limited to isometric and isotonic contractions founded on isolated muscle properties that do not always reflect how muscles function in vivo. Robert Josephson incorporated lengthening contractions into a work loop analysis that shifted the focus to dynamic muscle function, varying force, length and work done both by and on muscle during a single muscle work cycle. It became apparent that muscle is both a force generator and a spring. Titin, the missing filament in the sliding filament model, is a muscle spring, which functions very differently in cardiac versus skeletal muscle; its possible role in these two muscle types is discussed relative to their contrasting function. The good news for those of us who choose to work on skeletal muscle is that muscle has been reluctant to reveal all of its secrets.

Why Do Knuckle‐Walking African Apes Knuckle‐Walk?

“…Specimens from the Hamann-Todd Osteological collection, Cleveland Museum of Natural History, Cleveland, OH. reviews by Lieber, 2002;Lorenz and Campello, 2012;Lindstedt, 2016;Roberts, 2016;Biewener, 2016).…”

“…The MTU is composed of active contractile (sarcomeres) and passive collagen‐rich elastic components (Hill, ) that, when recruited, exert tension. While muscle contraction is a metabolically expensive function that can be documented electromyographically, recruitment of the muscle's passive elastic elements (its epimysium), and its tendons, can both store and release energy in order to dampen impulse loading (Roberts et al, ; see reviews by Lieber, 2002; Lorenz and Campello, 2012; Lindstedt, ; Roberts, ; Biewener, ).…”

Electrical Impedance Monitoring of C2C12 Myoblast Differentiation on an Indium Tin Oxide Electrode

“…Skeletal muscle, the largest organ of the body, constitutes 40%–50% of the total body mass and plays an important role in movement, insulation of internal organs, and metabolism [1,2]. Impairment of muscle function can lead to many pathological changes including diabetes, obesity, and muscle wasting, as well as aging [3,4,5].…”

Back to the future! Revisiting the physiological cost of negative work as a team-based activity for exercise physiology students

“…Most notably, the smaller Brenda Bigland was able to use considerably less effort to resist and tire out the forward pedaling efforts of the larger Murdoch Ritchie. This groundbreaking study offered a new viewpoint on muscle energetics specifically during human whole body exercise, and the story of the two-bicycle singlechain "push-me, pull-you" setup has been passed on in the literature (4,11,24,27,36,37). Our laboratory activity not only educates students about muscle lengthening contractions, which are covered albeit briefly in exercise physiology textbooks, but also preserves the history of this original experiment.…”