Too Much of a Good Thing: The Midlife HIIT Rules

By Maria Lally

HIIT, which stands for high-intensity interval training, has been a fitness favorite for a while now, given its premise that short bursts of intense exercise burn more fat and build more muscle than longer, steadier workouts, meaning more results in less time. However, while the benefits of HIIT are widely known, is there a tipping point?

Proving you really can have too much of a good thing, a new study led by Jinger Gottschall, associate professor of kinesiology at Penn State University, found that the benefits of the hugely popular HIIT workouts dwindle if you do them too often – and can even be harmful. According to Gottschall, “Individuals with a high volume of HIIT training were unable to reach their maximum heart rate regularly and complained of symptoms related to overtraining.” HIIT aficionados run the risk of extreme overload, delayed onset muscle soreness (DOMS), injury and heart problems, especially those who are new to working out, or over 40.

So with that in mind, here are the midlife HIIT rules:

Start slow

“In terms of cardio gains, weight and fat loss, and general gains in overall fitness and health, HIIT produces fantastic results for most people,” says personal trainer Matt Roberts. “However, if you’re new to working out, don’t do HIIT. Use a little interval training in your workouts, yes, do some weight training, yes, but don’t do true HIIT. Not until you’ve been exercising fairly regularly for at least a month. After this you can start doing HIIT once a week, and then after another month you can build up – if you wish – to doing it two or three times a week. It’s not a good method for beginners.”

Set limits

“Even if you’re reasonably fit and able to do HIIT without too many problems, three sessions a week is more than enough for most people, even very fit ones,” says Roberts. “Any more than that is probably too much.” This is in line with Professor Gottschall’s study, whose findings were presented at the American College of Sports Medicine’s annual conference, where she called for a weekly upper limit for HIIT fans.

Track your heart rate

Whether you use a Garmin, Fitbit or even the standard heart rate monitor on your phone, Roberts says the easiest way to tell if you’re overdoing it during a HIIT session is to invest in a fitness tracker. “These are a really good guide to whether you’re pushing things a little too far.”

As a rule, HIIT workouts push your heart rate above 85% of your maximum. “Raising your heart rate to 85% of the maximum is fine,” he advises, “but only provided your recovery heart rate comes down to 65-70%. The danger lies in not giving yourself sufficient recovery time between peaks of intensity to get your heart rate down again. An adequate rest period varies from person to person, depending on their overall health and fitness levels. There is no one-size-fits-all.”

Don’t push yourself (especially if you’re a man)

Roberts continues, “There’s such a thing as too much of a good thing, and this goes for HIIT as well. When a person exercises to exhaustion, whether through marathon training or extreme HIIT, it can impact their body’s ability to use testosterone. And since testosterone naturally declines with age, if you’re a man over 40 and you do HIIT too often you may affect your ability to regenerate testosterone levels.”

Another reason to stick to the thrice-weekly limit.

Keep it short

The whole point of HIIT is short but intense bursts of activity, so don’t be tempted to prolong things. “I was surprised by the obvious difference between doing 30 minutes [of HIIT] and doing more than 45 minutes,” says Professor Gottschall. “The difference in performance, stress-related feelings, and sleep quality was significant.” More than 40 minutes of high-intensity exercise can also increase your risk of injury.

Add yoga to your weekly workouts

People often come to yoga to gain flexibility, but the more beneficial aspect to athletes is that of mobility – an increased range of motion in joints and muscles – while maintaining strength and control in that full range. By adding yoga to your routine, you help break down patterns of tightness and tension that build up in your body during HIIT and reduce the likelihood of injury. It’s the perfect complement for improving overall fitness and well-being.