It’s a secret that pro athletes and elite sports people have long had up their sleeves: High-Intensity Interval Training (HIIT) gets results. Now, an increasing number of everyday fitness enthusiasts are looking to use HIIT to getting super fit, super fast. To satisfy this demand, savvy fitness facilities all around the globe are adding HIIT workouts to their offerings, and reaping the rewards.
HIIT-based workouts are hard work, but they’re over quickly. A typical HIIT workout is just 30 minutes, featuring short bursts of high-intensity activity interspersed with recovery periods. Studies have shown that this interval training is an ideal way to increase fitness, build muscle and help lose fat. How? By pushing the line between aerobic and anaerobic energy use. Your anaerobic energy threshold is the point at which your body reaches its maximum oxygen intake (VO2 Max.)
VO2 Max is your maximum level of aerobic fitness and seady-state training ticks along at a comfortable rate just below it. The interval periods of HIIT push you closer to it, which has two effects. First, it triggers the “after burn,” where your body continues to burn oxygen, and therefore calories, hours after exercise. Second, it increases your VO2 Max. In other words, once you hit your anaerobic threshold, the body then relies on energy other than oxygen to keep going, giving you only about three minutes at that intensity. Every time that happens, your body adapts by enabling you to use oxygen at higher intensities. As your VO2 Max goes up, you can then work out at that intensity aerobically, continuing to burn oxygen. You can work out harder, for longer.
A 2006 study divided middle distance runners into three groups training at different intensities and found that the group undergoing a HIIT workout had a stronger after burn, which lasted up to nine hours post-training.
In addition, HIIT engages more muscle fiber in each workout: steady-state training works predominantly slow-twitch muscle fiber, creating the lean “marathon runner” look. But a lot of our muscle is made up of fast-twitch fiber, which operates anaerobically. HIIT is a great way of reaching these fibers. Think of a sprinter: Usain Bolt hits VO2 Max off the blocks. The difference between steady-state training and HIIT could be illustrated by thinking about different physiques — a lean marathoner versus a muscular sprinter.
It might seem counter-intuitive that HIIT workouts lead to greater fat loss than steady-state training, as it’s commonly accepted that more fat is burned during moderate-intensity exercise, but fat loss through HIIT is aided by the after burn and hormonal responses. For instance, higher levels of human growth hormone — which promotes fat burning — are present due to higher intensity work for your large muscle groups.
Recent research by Dr. Jinger Gottschall and Pennsylvania State University highlights how HIIT can get you fitter, faster while you spend no extra time working out. This research tested 84 fit adult exercisers split into two groups. Both groups engaged in five hours of quality, professionally-designed exercise per week.
The point of difference was that one group substituted an hour of cardio for two 30 minute HIIT sessions. After six weeks, all participants recorded increases in cardiovascular fitness and strength while decreasing triglycerides, decreasing body fat and reducing waist circumference.
Those who did the HIIT workouts enjoyed these benefits at more than twice the rate across all measures. The fact that HIIT workouts are quicker and offer better results than other forms of exercise can only fuel the attractiveness of the HIIT trend. The workouts are hard, they’re not for everybody and they’re not for every day. But given their increasing popularity, adding a HIIT offering is something that every club should consider.
Les Mills is the world’s largest provider of group fitness and team training programs, including the popular LES MILLS GRIT™, a series of high-intensity interval training workouts. For more information, visit www.lesmills.com.
