Topics:
Animal Physiology, Animal Refresher
Immediate Energy Source for Muscle Contraction (First 4 Seconds)
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Question (English)
Immediate source of energy for muscle contraction (up to first 4 seconds) is:
- ATP ✓ Correct
- Glucose
- Glycogen
- Creatine phosphate (CP)
Explanation:
Correct Answer: ATP
ATP (Adenosine Triphosphate) is the immediate and direct energy source for muscle contraction. During the very first 1–4 seconds of exercise, the small amounts of ATP already stored in the muscle fiber are used directly.
Three Energy Systems for Muscle Contraction
| Energy System | Time Duration | Fuel | Example |
|---|---|---|---|
| ATP-CP system | 0–4 sec (ATP); 4–10 sec (ATP + CP) | Stored ATP, then Creatine Phosphate | 100m sprint, high jump |
| Lactic acid system (Anaerobic glycolysis) | 10–45 sec; 45 sec–2 min | Muscle glycogen | 200–400m race |
| Aerobic/Oxidative system | 2 min → several hours | Muscle glycogen + Fatty acids | Marathon, >3km race |
Note: After 4 seconds, creatine phosphate (CP) donates its phosphate to ADP to regenerate ATP (via creatine kinase). This is still anaerobic and very fast.
Why Other Options Are Wrong
- Glucose → Used in the lactic acid system (anaerobic glycolysis); requires more steps; not immediate.
- Glycogen → Storage form of glucose; takes longer to mobilize; used in intermediate and prolonged exercise.
- Creatine phosphate → Used in 4–10 seconds range to replenish ATP; not the immediate 0–4 second source.
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
