Yes, we know it's good for us but trying to squeeze in an hour at the gym in between a 40-hour work week, family commitments, and a social life can feel near-on impossible. That's where high-intensity interval training (or HIIT) comes in.
HIIT workouts have become increasingly popular in recent years. If you've never heard the term before, it involves a series of short bursts of very intensive exercise designed to get your heart racing broken up by brief periods of rest. With HIIT, exercisers can achieve the same health benefits you can expect from more traditional exercises – in half the time.
Now, researchers have studied the mitochondrial responses of gym-goers and discovered that just 2 minutes (yes, you read that right – 2 minutes) of HIIT can produce similar responses as a solid half an hour of moderate-intensity aerobic exercise (think: cycling, basketball, and brisk walking). Their results have been published in the American Journal of Physiology.
The researchers recruited eight young adult volunteers to take part in three exercise sessions of different intensities, calculating exactly how much energy they expended in each session and measuring any mitochondrial changes that took place during the workout. To do this, they compared a muscle biopsy taken from the volunteer's thigh before the workout, immediately after the workout, and three hours post workout.
The moderate intensity workout involved 30 minutes of continuous cycling at 50 percent peak effort. The high-intensity interval workout was five 4-minute cycling sessions at 75 percent peak effort with a 1-minute rest in between each burst. And the most vigorous training, sprint cycling, involved four 30-second cycling sessions at 100 percent peak effort and a 4.5 minute resting period in between each go. To avoid "contaminating" the results, the exercise sessions were spread out over a period of weeks with seven days or more of rest in between each workout.
Analyzing the results, the researchers noticed that levels of hydrogen peroxide (JH2O2.) changed post-exercise – reading lower immediately post-exercise and elevated three hours later. The opposite occurred for high-resolution mitochondrial respirometry (JO2), which read higher immediately post-exercise and had decreased three hours later. Too much reactive oxygen species can harm cells but in the levels detected after the workouts, it may promote cell responses that help rather than hinder metabolic function the study authors say.
What's more, there did not seem to be a significant difference in mitochondrial response between each of the three workouts, suggesting a 2-minute workout at an extremely high intensity can yield the same results as half-an-hour of endurance. Good news for busy bees.
"This suggests that exercise may be prescribed according to individual preferences while still generating similar signals known to confer beneficial metabolic adaptions," the study authors write. "These findings have important implications for improving our understanding of how exercise can be used to enhance metabolic health in the general population."
But if you want your exercise to boost your brain power, you might want to stick to running.