Muscle Fatigue
...’t any oxygen available in the cells for aerobic respiration. This buildup of lactic acid, as a product of this anaerobic respiration, reaches a point where the muscles has a reduced ability to contract, until eventually exhaustion sets in and contraction of the muscle will stop. This is muscle fatigue. Similarly, in the case of the automobile when the waste products (exhaust) cannot be removed and is built up inside the engine, the automobile will stop (stall). The ability to move parts of the body in opposite directions require that muscles be attached to the skeleton in antagonistic pairs, each muscle working against the other. In humans, contraction of the biceps muscle raises (flexes) the forearm. Contraction of the triceps muscle lowers (extends) the forearm. Every time...