Ca 2+ accumulation and cell damage in skeletal muscle during low frequency stimulation

Abstract

Electrical stimulation has been shown to produce a marked increase in Ca2+ influx and Ca2+ content in rat skeletal muscle. Long-term low-frequency stimulation (1 Hz, 240 min) increased 45Ca uptake by 30% and 154% in soleus and extensor digitorum longus muscles, respectively. Studies using Ca2+-fluorescent dyes have shown that intracellular concentrations of free Ca2+ are increased up to threefold during long-term low-frequency stimulation, suggesting that muscle cells have difficulties in handling the Ca2+ taken up during stimulation. Furthermore, long-term low-frequency stimulation induces leakage of the intracellular enzyme lactate dehydrogenase from the muscles. This leakage may reflect degradation of membrane proteins by the Ca2+-activated neutral protease calpain. This, in turn, leads to further influx of Ca2+ and further acceleration of protein breakdown. Membrane leakages are likely to result in sensations of pain in the damaged muscle. It is suggested that Ca2+ plays a central role in the development of muscle fibre injury during prolonged muscle activity of workers using a computer mouse.

In vivo imaging of intracellular Ca2+ after muscle contractions and direct Ca2+ injection in rat skeletal muscle in diabetes

“…In fact, previous studies indicate that [Ca 2ϩ ] i accumulation may not occur following shorter bouts of isometric tetanic contractions (7). On the other hand, longerlasting bouts of fatiguing muscle contractions do elicit muscle [Ca 2ϩ ] i accumulation (11,27,28,47 greater and occurred after fewer bouts of contractions compared with that in CONT. However, it is unlikely that these responses are directly responsible for the DIA tension deficits.…”

Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks

“…Static contractions of proximal musculature, often combined with dynamic contractions of the distal musculature, are known to form a high risk with respect to UEMSDs (Bernard 1997, Sluiter et al 2000. Physiological lines of evidence suggest that sustained contractions of arm and neck muscles even at relatively low intensities may explain this association (Gissel 2000, Ha¨gg 2000, Sjøgaard et al 2000.…”

Mechanisms of exercise-induced muscle damage and fatigue: Intracellular calcium accumulation

“…Thus, whereas less prolonged, moderate-intensity ISO contractions may produce no detectable increase in resting [Ca 2+ ] i in single muscle fibers 22) , severe chronic ISO stimulation induces gradual [Ca 2+ ] i accumulation, and may be associated with muscle fatigue 1,23) . Differing from smooth muscle and cardiomyocytes, the influx of extracellular Ca 2+ , across the sarcolemma, does not contribute significantly to excitation-contraction coupling in skeletal muscle, at least not during acute activation.…”

“…In non-fatigued and non-damaged muscle fibers, as the muscle relaxes following contraction, [Ca 2+ ] i decreases immediately. However, repeated contractions induce muscle fatigue (often assessed as the reduction of tetanic force), muscle fiber damage, and prolonged elevation of [Ca 2+ ] i after contraction(s) 1,2) . Here, as illustrated in Fig.…”