For seniors seeking health boost, high-intensity workouts may ‘HIIT’ the spot

High-intensity interval training appears more effective at preserving lean muscle mass while reducing body fat in older adults compared to moderate-intensity exercise, according to recent research.

The six-month study out of the University of the Sunshine Coast and the University of Queensland tracked more than 120 healthy Australian seniors as they completed three weekly exercise sessions at varying intensities. Participants averaged 72 years old with body mass indexes around 26, considered normal for adults over 65.

“We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle,” said Dr. Grace Rose, the study’s lead author and an exercise physiologist at UniSC, in a press release.

The distinction matters because body composition plays a significant role in chronic disease development as people age. While moderate-intensity training successfully reduced fat mass, it also led to small declines in lean muscle tissue. High-intensity training avoided this tradeoff.

Both high and moderate intensities were associated with reductions in visceral fat, the type that accumulates around internal organs. However, only the high-intensity approach maintained muscle mass throughout the intervention period.

“High intensity training in this study involved repeated short bursts, or intervals, of very hard exercise – where breathing is heavy and conversation is difficult – alternated with easier recovery periods,” said Associate Professor Mia Schaumberg, a co-author and UniSC physiology researcher. “HIIT likely works better because it puts more stress on the muscles, giving the body a stronger signal to keep muscle tissue rather than lose it.”

The study, published in the journal Maturitas, involved collaborators from UniSC’s Healthy Ageing Research Cluster and the University of Queensland. Participants were randomized into three groups: high-intensity interval training, moderate-intensity continuous training, or low-intensity exercise serving as an active control.

Each group attended supervised 45-minute sessions three times weekly for six months. Researchers used dual-energy X-ray absorptiometry scans to measure body composition at baseline, three months, and six months.

Researchers cautioned that while statistically significant, the changes in body composition were small and did not reach clinically meaningful thresholds for most participants on average.

The findings add to growing evidence that exercise intensity matters for body composition outcomes in older populations. Previous research has shown mixed results, often focusing on younger adults or people with existing health conditions.

Researchers acknowledged the study’s limitations, including closer-than-expected heart rate ranges between intensity groups and the inability to examine sex-specific responses due to sample size constraints. They suggested future studies combine high-intensity aerobic training with progressive resistance training to optimize muscle preservation in aging adults.

The work was funded entirely by the Stafford Fox Medical Research Foundation.