EPOC / "Afterburn" (Accurate Account)

Excess post-exercise oxygen consumption (EPOC) is the elevated oxygen uptake — and therefore elevated energy expenditure — that persists after exercise ends, as the body restores itself toward resting conditions: replenishing phosphocreatine (see Replenishing the ATP-PC Source (Alactacid Half-Life Curve)), clearing metabolites, restoring oxygen stores, and handling elevated temperature and hormones. It is the modern, accurate framing of the older "oxygen debt" idea, and it is driven by the Oxygen (Aerobic) Energy System.

The honest magnitude. EPOC is real but small relative to the workout itself:

• It is typically on the order of ~6–15% of the calories burned during the session (often cited around ~7%). So a 500 kcal workout might add roughly ~35 kcal afterward.
• Across studies, total EPOC after interval or resistance sessions commonly lands in the range of ~50–200 kcal, and many studies find far less (one HIIT study showing a 14% metabolic-rate rise translated to only ~32 kcal).
• After a typical 30–45 min moderate session, the elevated metabolism over the following ~45 min might add only ~15–20 kcal — comparable to a few minutes of walking.

The myth to avoid. Marketing claims that "the afterburn burns more than the workout" or that EPOC makes intense workouts a metabolic free lunch are false; the absolute EPOC simply isn't large. Higher-intensity work (HIIT/SIT; see HIIT (High-Intensity Interval Training), SIT (Sprint Interval Training)) does produce somewhat more EPOC than easy steady-state, but the difference is measured in tens of calories, not hundreds. For body composition, what dominates is total energy balance — calories in vs. calories out across the whole day (see Exercise and Caloric Expenditure (Total Work) and Caloric Balance (Energy Balance)) — not the afterburn.

• EPOC = elevated post-exercise oxygen uptake/energy expenditure restoring the body to rest.
• Magnitude ~6–15% of session calories (≈7% typical): a 500 kcal workout adds ~35 kcal.
• Total EPOC commonly ~50–200 kcal after intervals/resistance; often much less.
• Higher intensity → somewhat more EPOC, but the difference is tens of calories, not hundreds.
• Total daily energy balance, not the afterburn, governs body composition.