Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.

Isometric, isotonic, and isokinetic exercises refer to the different techniques for activating and strengthening muscles. Isometric exercises, like planks, involve activating muscles with no movement.

Introduction It has been shown that caffeine promotes vigilance, attention, mood and arousal 5. The potential mechanisms of caffeine’s action include its role as an adenosine receptor antagonist that ...

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