6.3.6 Investigating Muscle Fatigue

Key Causes of Muscle Fatigue

1. ATP Depletion:

• ATP is required for muscle contraction and relaxation. Prolonged activity reduces ATP levels.

2. Lactic Acid Accumulation:

• Anaerobic respiration during intense exercise produces lactic acid, which lowers the pH of muscle cells and inhibits enzyme activity.

3. Reduced Calcium Ion Availability:

• Calcium ions are essential for muscle contraction. Fatigue can reduce their release or uptake in muscle cells.

4. Neuromuscular Junction Fatigue:

• Prolonged activity may deplete neurotransmitters such as acetylcholine, affecting signal transmission.

Investigating Muscle Fatigue

1. Using a Handgrip Dynamometer:

• Measures the force of grip over time to assess muscle fatigue.
• Results show a decline in force as fatigue develops.

2. Procedure:

• Grip the dynamometer with maximum force for a set duration (e.g., 1 minute).
• Record the force exerted at regular intervals (e.g., every 10 seconds).
• Plot a graph of force against time to identify the point at which muscle fatigue occurs.

3. Using EMG (Electromyography):

• Monitors electrical activity in muscles during contraction.
• A decrease in signal amplitude over time indicates muscle fatigue.

Factors Affecting Muscle Fatigue

1. Exercise Intensity:

• Higher intensity causes faster ATP depletion and lactic acid build-up.

2. Duration of Activity:

• Longer durations deplete energy reserves and neurotransmitters.

3. Fitness Level:

• Fitter individuals typically experience slower onset of fatigue due to higher aerobic capacity and better removal of waste products.

4. Diet:

• Carbohydrate-rich diets improve energy availability.

5. Environmental Conditions:

• Heat and dehydration can accelerate fatigue.

Application

• Sport Science: Understanding fatigue can help athletes improve performance through tailored training and recovery strategies.
• Medical Research: Studying fatigue helps in managing muscle-related disorders, such as chronic fatigue syndrome and muscular dystrophy.