HIIT vs long workouts: Which is better for metabolic health?

• Walking in short bursts or climbing stairs can burn 20% to 60% more energy than sustained activity for the same distance, a new study has found.
• Researchers at the University of Milan, in Italy, enrolled 10 participants with an average age of 27 who were subjected to 10- to 240-second bursts of treadmill walking or stair-climber rounds.
• Experts caution that the findings cannot be broadly applied due to the small number of participants and their relatively young, healthy status.

Walking for short bursts or climbing stairs can burn 20% to 60% more energy than sustained activity for the same distance, a new study published in the Proceedings of the Royal Society B has found.

Researchers at the University of Milan, in Italy, wanted to understand how walking’s metabolic cost was affected by the duration of the activity.

To this end, they recruited 10 participants with an average age of 27, who were agreed to undertake 10- to 240-second bursts of treadmill walking or stair-climber rounds.

Using an oxygen mask to measure oxygen uptake and metabolic cost, they determined that the shorter bouts of activity had greater metabolic cost, with 30-second bouts consuming 20% to 60% more oxygen than steady bouts of activity.

The researchers concluded that by starting and stopping activity, the participants were able to expend more energy due to the metabolic processes that the body encounters while ramping up to strenuous bursts versus the sustained energy use of longer bouts.

In their view, people looking to maximize their exercise returns might consider implementing shorter bursts of activity rather than a longer sustained effort.

Ryan Glatt, CPT, NBC-HWC, a senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in Santa Monica, CA, who was not involved in the study, told Medical News Today that the study’s claim of higher energy expenditure hinges on what he referred to as “specific circumstances.”

“While shorter bursts might burn more calories, the actual benefit may vary depending on individual metabolism and exercise habits,” Glatt said, adding that the implications for similar short-burst activity like high-intensity interval training (HIIT) are also unclear.

”The study implies HIIT could burn more calories due to frequent stopping and starting, but it’s not conclusive. While HIIT can be effective, the benefit over traditional workouts might not be as significant for everyone,” he cautioned.

Christopher A. Schneble, MD, an assistant professor of orthopaedic surgery at the Yale School of Medicine, who was also not involved in the study, told MNT that the study’s conclusions cannot be applied broadly to any general form of workout because of the emphasis on shorter activity times.

“We have to keep in mind that this study only looked at very short exercise durations, those between 10 seconds and 4 minutes. We can’t necessarily apply this concept to longer durations. The authors more or less hint at there being a potential phase of energy inefficiency with increased oxygen intake very early into a workout. Their results suggest that on average, we are disproportionately using more oxygen within the first 30 seconds of exercise, however most of this phenomenon corrects back to a steady state within the first few minutes.”

– Christopher A. Schneble, MD

“The authors’ findings apply more to situations of starting exercise, like going for intermittent short walks, than they do for sustained exercise,“ Schneble explained.

“The increased energy expenditure and oxygen intake during the initial 30s of working out is interesting, but don’t think it makes sense to prioritize your workouts around this phenomenon given it is so short lived, and you may find yourself waiting spending more time recovery periods than actually exercising,” he advised.

Given the relatively young average age of the participants — of which there were only 10 — the study’s findings may not apply broadly to a general population, Schneble said.

“I don’t know that we can conclude very much from this article about the role age plays in influencing the results. We also have to consider how these results might vary based on physical fitness, which can have a substantial impact on maximum oxygen consumption, [which is the] amount of oxygen we can make available for maximum intensity,” he pointed out.

“What I found particularly interesting was that regardless of the activity, there was an initial over intake of oxygen more often in excess of the eventual intake required down downstream. To some degree, this could be our bodies doing their best to put us in a situation to be ‘overprepared’ for bursts of physical activity, but a lot more research is needed to get down to the bottom of this and understand what drives this finding,” said Schneble.

Glatt also emphasized the lack of diversity in the study’s ability to infer larger trends among broad populations.

“The study doesn’t explore age-related differences, so it’s unclear if younger people, with higher energy levels, gain less from short bursts than older adults. More research is needed to verify any age-based outcomes,” he told us.

“With only 10 participants, the findings are far from definitive. The small sample size limits the study’s reliability and broader applicability. More data is needed to draw solid conclusions,” Glatt pointed out.