How Little Interval Training (HIIT) Do You Need for Most of the Benefit?

Overwhelming evidence supports an association between higher cardiorespiratory fitness, measured by VO2max, and lower rates of chronic disease and premature death.

Numerous studies have demonstrated that high-intensity interval training (HIIT) is more time-efficient than longer periods of moderate-intensity exercise for improving VO2max.

HIIT involves alternating short periods of intense activity, such as running or cycling hard, with periods of easier activity or rest. Moderate-intensity continuous training (MICT), by comparison, involves sustained exercise at a lower intensity, often comparable to Zone 2 training.

But how much time do you actually need to spend exercising to get most of the benefit of HIIT?

A new meta-analysis combined the results of 69 randomized studies involving 2,387 participants.

Both HIIT and MICT improved VO2max, but the most interesting finding was how little time was required. The researchers found that HIIT sessions lasting just 11 minutes achieved approximately 80% of the maximum predicted improvement in VO2max. Longer sessions produced diminishing returns, with relatively little additional improvement beyond about 23 minutes.

By comparison, moderate-intensity continuous training required almost five times the commitment per session (approximately 52 minutes).

That means HIIT can provide substantial improvements in cardiovascular fitness in about one-fifth the exercise time. And those 11 minutes include recovery periods between the intense efforts, although not warm-up or cool-down. Depending on the interval protocol, that could mean only about 5 minutes of actual high-intensity exercise.

For those with limited exercise time, the message is clear: short HIIT sessions are an exceptionally efficient way to improve cardiovascular fitness.

But longer, moderate-intensity exercise remains valuable. Both HIIT and MICT improved cardiometabolic risk factors, and longer aerobic sessions provide additional endurance benefits in a training program that brief intervals cannot fully replace.