GE 345: Week 4

Fun Muscle Facts

    Physiology/Kinesiology

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| Potential | Skeletal Muscle | Myofibrils, NM Interaction | Contraction | Fun Facts | |

Muscle Fatigue

• Contractile & metabolic processes unable to continue supplying same work output.
• Muscle fatigue almost directly proportionate to muscle glygogen depletion.
• Occasional diminished nerve signal transmission following prolonged muscular activity.

Muscle Soreness

• Microtears in muscle fibers.
• Lactic acid is used up almost immediately after activity ceases enough for oxygen to be used again, so is not present in delayed onset soreness.

Adaptation

Cell constituents are constantly being repaired and replaced. The contractile proteins in a muscle fiber can be completely replaced in as little as 2 weeks. Muscle adapts to repeated contractions over time by altering length, strenth, vascular supply, etc.

• Overload, or regularly stressing muscles in a progressive manner, causes hypertrophy: muscle mass increase due to increase in number of myofibrils in the muscle fiber. Mitochondria also grow and multiply to create more energy.
• Disuse can result in detraining, or atrophy: muscle mass decreases due to decay of contractile proteins and therefore a decrease in the number of myofibrils.

| Potential | Skeletal Muscle | Myofibrils, NM Interaction | Contraction | Fun Facts | |