Source notes

A short, all-out effort does not rely on just one energy system. Drawing on 102 studies of maximal exercise in adults, researchers modeled energy supplied through aerobic pathways, which use oxygen, and anaerobic pathways, which do not directly use it. For a single 60-second maximal effort, the model estimated 42% aerobic and 58% anaerobic contribution. Total contributions were roughly equal for efforts lasting 75–80 seconds. These are estimates across studies, mainly involving younger, trained men running or cycling, rather than precise measurements of what happens in every person's workout.

Both systems contribute from the start. The estimated crossover does not mark a switch that turns oxygen use on. The percentages add up energy supplied over the entire effort, rather than describing only its final second. Duration helps explain the changing balance, but measurement methods and exercise conditions also matter. An effort can be predominantly anaerobic without making its aerobic contribution negligible.

How Does This Show Up in Real Life?

Consider a hard effort lasting about a minute. Calling it anaerobic may be convenient, but the label can hide a substantial contribution from oxygen-supported energy production. The useful question becomes what demands the event places on the body, rather than which single system it belongs to. The authors suggest that understanding this mixture can inform how sporting demands are interpreted. However, a set of repeated intervals with recovery breaks is not the same situation as the single maximal bouts analyzed here. Nor is an ordinary minute of walking equivalent to a minute performed all out. The estimates therefore cannot be pasted onto a whole workout or turned into a recommended split of training time. Energy contribution during an event is not proof of the best training plan for it.

Most studies were small and heavily weighted toward male participants and running or cycling. Anaerobic contribution depends on indirect estimates without a universally accepted measurement standard. The literature search ended in January 2020, despite publication in 2026. These limits make the broad pattern more dependable than an exact percentage for women, older adults, other exercise modes, or an individual athlete.

Why We Cite It

For Alpekin's exercise tools, the paper adds a separate measurement safeguard: recorded power, work, or performance time should not automatically be labeled an energy-system capacity. It supports naming outputs according to what was actually measured. That distinction matters when a clear-looking dashboard could otherwise imply more physiological precision than its data provide.

Use this work to make exercise categories less rigid, not to assign a laboratory percentage to yourself. It helps explain event demands and the limits of familiar labels. Deciding how to train still requires evidence about training outcomes, not just an estimate of energy supplied during one effort.