EFFECTS OF TRAINING ON POTASSIUM, CALCIUM AND HYDROGEN-ION REGULATIONIN SKELETAL-MUSCLE AND BLOOD DURING EXERCISE

Ionic regulation is critical to muscle excitation. contraction and met abolism, and thus for muscle function during exercise. This review foc uses on the effects of training upon K+, Ca2+ and Hf ion regulation in muscle and K+ regulation in blood during exercise. Training enhances K+ regulation in muscle and blood and reduces muscular fatiguability. Endurance, sprint and strength training in humans induce an increased muscle Na+, K+ pump concentration, usually associated with a reduced r ise in plasma [K+] during exercise. Although impaired muscle Ca2+ regu lation plays a vital role in fatigue, little is known about possible t raining effects. In rat fast-twitch muscle. overload-induced hypertrop hy and endurance training were associated with reduced sarcoplasmic re ticulum Ca2+ uptake. consistent with fast-to-slow fibre transition. In human muscle. endurance and strength training had no effect on muscle Ca(2+)ATPase concentration. Whilst muscle Ca2+ uptake, release and Ca (2+)ATPase activity were depressed by fatigue. no differences were fou nd between strength athletes and untrained individuals. Muscle H+ accu mulation may contribute to fatigue during intense exercise and is also modified by sprint training. Sprint training may increase muscle Lac( -) and work output with exhaustive exercise, but the rise in muscle [H +] is unchanged or attenuated. indicating a reduced rise in muscle [H] relative to work performed. Muscle buffering capacity can be dissoci ated from this improved H+ regulatory capacity after training. Thus. t raining enhances muscle and blood K+ and muscle H+ regulation during e xercise. consistent with improved muscular performance and reduced fat iguability: however. little is known about training effects on muscle Ca2+ regulation during contraction.