Energy Source During Strenuous Exercise up to 10 Seconds

During strenuous exercise up to 10 seconds, the energy comes from:

Correct Answer: Creatine Phosphate (CP)

During strenuous exercise lasting up to 10 seconds (after the initial 4-second ATP phase), energy is supplied by Creatine Phosphate (CP) via the ATP-CP (phosphagen) system. Creatine kinase rapidly transfers the phosphate group from CP to ADP to regenerate ATP.

Reaction:

Creatine-PO₄ + ADP → ATP + Creatine (catalyzed by Creatine kinase)

ATP-CP System Features

• Anaerobic (no oxygen required).
• Fastest energy replenishment system.
• Very limited capacity — exhausted within 10 seconds.
• Used for explosive, high-intensity activities (sprints, jumps, throws).

Why Other Options Are Wrong

• Fat → Used in prolonged aerobic exercise (>2 minutes); too slow for intense short-burst activity.
• Glucose → Part of glycolytic (lactic acid) system; takes longer to produce ATP than CP system.
• Protein → Last resort fuel used only during prolonged starvation; not used in short exercise bursts.