You breathe the hardest not when you’re lifting, but right after you finish a set and are resting—your body is catching up on oxygen debt built up during the effort.

Scientific Claim

In healthy, resistance-trained men, oxygen uptake during resistance exercise increases progressively across consecutive sets, with the highest values occurring during rest intervals rather than during active lifting, suggesting metabolic stress accumulates between sets.

Original Statement

“The O2 increased throughout the successive sets in all exercise protocols, which was mainly detected during the RIs (p < 0.001). The peak O2 associated with a given set always occurred in the first few seconds of the subsequent RI.”

From study:The effect of Between-Set Rest Intervals on the Oxygen Uptake During and After Resistance Exercise Sessions Performed with Large- and Small-Muscle Mass

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The study directly measured VO2 at set and RI intervals with statistical validation (p < 0.001), supporting definitive descriptive language about the pattern of oxygen uptake.

Evidence from Studies

Supporting (0)

No supporting evidence found

Contradicting (1)

The effect of Between-Set Rest Intervals on the Oxygen Uptake During and After Resistance Exercise Sessions Performed with Large- and Small-Muscle Mass

Randomized Controlled Trial

Human

2011 Nov

The study found that people breathe harder during the actual lifting, not during the breaks between sets — so the claim that oxygen use is highest during rest is wrong.

Source Study

The effect of Between-Set Rest Intervals on the Oxygen Uptake During and After Resistance Exercise Sessions Performed with Large- and Small-Muscle Mass

Score: 46

DOI: 10.1519/JSC.0b013e318212e415

Similar Assertions

You can make your workout feel harder and your muscles burn more by resting less between sets—but you can still lift the same total weight without getting weaker.

80%

Right after leg presses with only 1-minute breaks, your body gasps for air more intensely in the first minute than if you took 3-minute breaks—but this doesn’t happen with chest flys.

77%

To know how many calories you burn during a weightlifting session, you have to measure your breathing for at least 90 minutes after you finish—most of the burn happens after you’re done lifting.

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How long you rest between sets doesn’t usually change how long your body keeps burning calories after a workout—unless you do chest flys with long breaks, then it stops sooner.

73%

Whether you rest 1 minute or 2 minutes between sets, or train at real high altitude or with a mask, you can still lift the same total amount of weight without losing strength.

72%