- Recent research in the journal Medicine & Science in Sports & Exercise found that high-intensity exercise (HIIE) was more effective for improving aerobic fitness and cardiovascular health, and moderate-intensity continuous training (MICT) was better for long-term blood sugar control.
- This study adds to recent evidence that one exercise intensity is not superior to another, and there are good reasons to do both for overall health benefits.
High-intensity interval exercise (HIIE) has been the darling of the fitness world for the better part of the past decade because these quick, hard intervals can help you get fit fast. But a recent meta-analysis published in Medicine & Science in Sports & Exercise is a good reminder that for long-term metabolic health benefits, you need moderate-intensity endurance training, too.
As a refresher, a tall stack of studies shows that high-intensity exercise, such as high-intensity interval training (near-maximum efforts) and sprint-interval training (“all out” efforts)—brief bursts of hard exercise followed by a short period of rest—is a time-efficient way to boost your aerobic and anaerobic fitness, making you stronger and faster on a run.
HIIE also has myriad health benefits, such as improving insulin sensitivity, improving brain function, lowering your risk of cancer, and burning fat while helping you maintain lean muscle mass.
But there’s a catch. The health benefits of high-intensity training can be transient. Research shows that some of the favourable effects, such as improved blood sugar control, can drop back to previous levels 24 hours after exercise. And you’re only supposed to do a HIIT or SIT session two to three days a week—too much intensity increases inflammation in the body, which is bad for performance and health. You may be able to find the same content in another format, or you may be able to find more information, at their web site.
So what’s the best approach for long-term health improvement as well as fitness gains right now? A team of German researchers decided to pore through the current literature to examine the specific cardiovascular and metabolic benefits of both.
The scientists analyzed the results of 55 studies that examined the effects of HIIE and moderate-intensity continuous training (MICT) on seven different health outcomes:
- Aerobic fitness (measured by your VO2 max)
- Cardiovascular health (measured by endothelial function, or how well blood vessels respond to exercise demands)
- Body composition
- Blood pressure
- Blood lipids
- Inflammation
- Insulin and glucose (blood sugar) metabolism.
The meta-analysis found HIIE was more effective for improving both aerobic fitness and cardiovascular health. For long-term blood sugar control, however, moderate, steady-state exercise was superior.
Everything else was pretty much a draw, though there appeared to be some benefits unique to different age groups. For instance, HIIE had benefits for people ages 30 to 50 for reducing diastolic blood pressure and for those who already had elevated blood pressure. And SIT appeared to be particularly effective for lowering LDL cholesterol levels.
It’s also important to note that, though it appears that HIIE may have some advantages for fitness, these studies alone aren’t enough to draw that conclusion, says exercise training researcher Jamie Burr, Ph.D., associate professor at University of Guelph, HHNS, Ontario.
“It is important to note that the average study duration was only 9 +/- 5 weeks,” Burr says. “It begs the question as to whether HIIT is actually superior overall, or just superior at stimulating change quickly.”
The take-home message that is emerging from this analysis—as well as from a recent study, which also reported unique benefits from both types of exercise—is that there’s no one “best” way to workout. Making room for both high-intensity and steady-state endurance activity not only makes you a more well-rounded athlete but also provides a greater spectrum of health benefits.
