Skeletal muscle isometric

The compliance in series with the active force. Force exerted by the activated elements must be transmitted or borne by whatever structural elements are in series with them. In skeletal muscle there is clearly a tendon in series but not so with smooth muscle. In smooth muscle, the total length of contractile apparatus is broken up into individual cells with intercalating extracellular connective structures. In addition, the portions of the crossbridges in series with the pulling site must also be stretched before force can rise to isometric levels. Taken together, the... 

Ramsey, R.W. Street, S.F. (1940). The isometric length-tension diagram of isolated skeletal muscle fibers of the frog. J. Cell. Comp. Physiol. 15, 11-34,... 

There is probably no biological phenomenon that has excited more interest among biochemists than the movement caused by the contractile fibers of muscles. Unlike the motion of bacterial flagella, the movement of muscle is directly dependent on the hydrolysis of ATP as its source of energy. Several types of muscle exist within our bodies. Striated (striped) skeletal muscles act under voluntary control. Closely related are the involuntary striated heart muscles, while smooth involuntary muscles constitute a third type. Further distinctions are made between fast-twitch and slow-twitch fibers. Fast-twitch fibers have short isometric contraction times, high maximal velocities for shortening, and high rates of ATP hydrolysis. 

Adhikari BB, Wang K. 2001. S100A1 modulates skeletal muscle contraction by desensitizing calcium activation of isometric tension, stiffness and ATPase. FEBS Lett 497(2, 3) 95-98. 

Fish JS, McKee NH, Kuzon WM, Jr., Plyley MJ. The effect of hypothermia on changes in isometric contractile function in skeletal muscle after tourniquet ischemia. J Hand Surg Am 1993 18 210-7. 

Kraft, T., Mattei, T., Radocaj, A., Piep, B., Nocula, C., Furch, M., and Brenner, B. (2002). Structural features of crossbridges in isometrically contracting skeletal muscle. Biophys.J. 82, 2536-2547. 

Moderate aerobic exercise to improve cardiovascular conditioning is beneficial to maintain a slower heart rate, improve cardiac reserve, and maintain skeletal muscle function. Isometric exercise should be avoided. ... 

Caldesmon has been shown to reduce isometric tension in chemically skinned smooth or skeletal muscle fibers, thus clearly suggesting that it can influence contractility (Szpacenko et al., 1985 Pfitzer et al.. 

Smooth muscle fibers generate as much isometric force per cross-sectional area as skeletal muscle fibers with only 20% as much myosin (Murphy et al., 1974). There have been various possible explanations for this, including different mechanical properties of the myosin itself. Experiments with the in vitro motility assay provide insight into this possibility. 

Smooth and skeletal muscle myosins have important functional differences with respect to their motor activities and their regulation. The differences in motor properties are evident in the behavior of smooth and skeletal muscle myosins in an in vitro motifity assay. Purified smooth muscle myosin propels actin filaments at one tenth the velocity of skeletal muscle myosin and produces an average of 3-4 times more force per unit time period than skeletal muscle myosin, as measured by a micro-needle assay (Warshaw et al 1990, Van Buren et al 1994). These differences in the functional properties of smooth and skeletal muscle myosins at the molecular level parallel differences in the functional properties of smooth and skeletal muscle tissues. Smooth muscle tissues produce the same isometric force per cross-sectional area as skeletal muscle, but contain only one fifth as much myosin (Murphy et al 1974). In addition, the maximal shortening velocities of smooth muscle tissues are 1-2 orders of magnitude slower than those of skeletal muscles (Murphy et al 1997). 

The structure of the contractile unit is fundamental to the interpretation of the relationship between muscle length and isometric tension in skeletal muscle. Each sarcomere unit contains bipolar thick filaments with a central bare zone surrounded by pairs of actin filaments of opposite polarity. The actin filaments are anchored at Z-bands that are aligned in parallel. The length-tension behavior of skeletal muscle has been interpreted in terms of changes in the overlap between the thick eind thin filaments as... 

R. W. Ramsey and S. F. Street, The Isometric Length-Tension Diagram of Isolated Skeletal Muscle Fibers of the Frog, J. Cell Comp, Physiol 15, 11-34 (1940). 

Henriksson J, Katz A, Sahlin K. (1986) Redox state changes in human skeletal muscle after isometric contraction. J Physiol 380(1) 441-451... 

Ginz HF, laizzo PA, Girard T, et al. Decreased isometric skeletal muscle force in critically ill patients. Swiss Med Wkly 2005 135 555-561. 

Constantin-Teodosiu, D, Cederblad, G., and Hultman, E, PDC activity and acetyl group accumulation in skeletal muscle during isometric contraction. J. Appl. Physiol.,... 

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