How muscles resupply ATP
ATP powers contraction, but stored ATP lasts only seconds. The body resynthesizes it via three overlapping systems: phosphagen, anaerobic glycolysis, and aerobic metabolism.
Phosphagen
- fastest
- no oxygen
- dominates ~0–10 s
- high power, low capacity
Anaerobic glycolysis
- no oxygen
- dominates ~10 s–2 min
- produces lactate (not “waste”)
Aerobic
- uses oxygen
- dominates beyond minutes
- slower, huge capacity
What shifts the balance
Which system and fuel dominate depends on intensity, duration, training status, and substrate availability (glycogen, nutrition, recovery).
Quick guide (duration → dominant)
- 0–10 s → phosphagen
- 10 s–2 min → anaerobic glycolysis
- >2–3 min → aerobic (rule of thumb)
BALANS in practice
Different systems, one goal: keep ATP production matching the task.