Muscle force

Figure 3. Top panel Whole muscle force (x) and single fiber PCr (a, a) and ATP ( , ) concentrations at rest and after 10 and 20 sec of intermittent electrical stimulation at 50 Hz. Open symbols denote type I fibers closed symbols denote type II fibers. Bottom panel Glycogenolytic rates in type I and II fibers during the 20 sec stimulation period. The open bar denotes type I fibers the closed bar denotes type II fibers.

Lieber, R.L. Friden, J. (1993). Muscle damage is not a function of muscle force but active strain. J. Appl. Physiol. 74,520-526. 

Bershitsky, S. Y., Tsaturyan, A. K., Bershitskaya, O. N., Mashanov, G. I., Brown, P., Bums, R., and Ferenczi, M. A. (1997). Muscle force is generated by myosin heads stereo-specifically attached to actin. Nature 388, 186-190. 

Tamopolsky M, Cupido C. Caffeine potentiates low frequency skeletal muscle force in habitual and nonhabitual caffeine consumers. J Appl Physiol 2000 89 1719-1724. 

Muscle force can be elicited by nerve stimulation to test both muscle function and the integrity of the nerve-muscle connection or by direct muscle stimulation to evaluate only muscle contractile independent of the synapse. The latter measure reflects the total force that the muscle is able to generate, if it is significandy... 

Thiermann, H., Worek, F., Szinicz, L., Eyer, P. (2005). Effects of oximes on muscle force and acetylcholinesterase activity in isolated mouse hemidiaphragm exposed to Paraoxon. Toxicology 214 190-7. 

Christiansen SP, Becker BA, laizzo PA, et al. Extraocular muscle force generation after Ricin-mAb35 injection implications for strabismus treatment. JAAPOS 2003 7 1-6. 

Mehta D, Wu MF, Gunst SJ (1996) Role of contractile protein activation in the length-dependent modulation of tracheal smooth muscle force. Am J Physiol 270 C24352 Meiss RA (1992) Limits to shortening in smooth muscle tissues. J Muscle Res Cell Motil 13 190198... 

Tonic seizures occur mostly In children and are characterized by Increased tone In extensor muscles, resulting in falling to the ground. Although brief, the duration of contractions Is somewhat longer than In myoclonic seizures. Vocalization may occur as a result of contraction of thoracic muscles, forcing air past the larynx. Brief periods of apnea and postictal tiredness may be associated. 

Description of muscle contraction has essentially evolved into two separate approaches — lumped whole muscle models and specialized crossbridge models of the sarcomere. The former seek to interpret muscle s complex mechanical properties with a single set of model elements. Muscle experiments measure muscle force and length subjected to isometric (fixed length) conditions, isotonic (fixed load) conditions, and transient analysis where either length or load is rapidly changed. 

Muscle force generation is believed to arise from the formation of crossbridge bonds between thick and thin myofilaments within the basic building block of muscle, the sarcomere. These structures, in the nanometer to micrometer range, must be viewed by electron microscopy or x-ray diffraction, limiting study to fixed, dead material. Consequently, muscle contraction at the sarcomere level must be described by models that integrate metabolic and structural information. 

This model was subjected to a wide range of loading conditions. A single set of model parameters is sufficient to describe the main features of isometric, isotonic, and quick release and stretch experiments. The model is sensitive to mechanical disturbances, consistent with experimental evidence from muscle force curves [34], aequorin measurements of free calcium ion [35], and high-speed x-ray diffraction studies [36]. The model is also consistent with sarcomere length feedback studies [29] where reduced internal motion delays relaxation. 

Muscle force transients arising from rapid (but small) changes in muscle length during otherwise isometric contractions may be described by expanding the model as the ventricle model was expanded to incorporate the ejection effect ... 

Huxley, A.F. and Simmons, R.M. 1973. Mechanical transients and the origin of muscle force. Cold Spring Harbor Symp. Quant. Biol. >7-. 669-680. 

The major requirements for successful locomotion are (1) production of a locomotor rhythm to ensure support to the body against gravity (2) production of muscle forces that will result with the friction force required for propelling it to the intended direction (3) dynamic equilibrium of the moving body and (4) adaptation of these movements to meet the environmental demands and the tasks selected by the individual. 

Karduna A.R., Williams G.R., Williams J.I. et al. 1996. Kinematics of the glenohumeral joint influences of muscle forces, ligamentous constraints, and articular geometry. /. Orthop. Res. 14 986. 

Neptune, R.R., Zajac, F.E., and Kautz, S.A., Muscle force redistributes segmental power for body progression during walking, Gait Posture, 19,194,2004. 

Schoenberg, M., Geometrical factors influencing muscle force development 1. The effect of filament spacing upon axial forces, Biophys. J., 30,51 7,1980. 

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