Aerobics classes became a fitness trend in the 1970s, and are still very popular. For decades, it was believed that exercising at a moderate-intensity continuous or steady state was the best way to burn calories and lose fat. Now we know that spending more time exercising isn’t always better. A short-duration type of exercise called high-intensity interval training (HIIT) has been found to be more effective for fat burning and muscle preservation.
HIIT is not a new form of exercise. Earlier versions with different names originated in the 1960s. What’s bringing it into the spotlight is the abundance of scientific studies supporting its benefits over traditional, lengthier cardio workouts. Is HIIT the best kind of exercise? Should you abandon aerobic exercise? Let’s take a look.
HIIT is a series of short spurts of high-intensity exercises and slower-paced active recovery. The aim of HIIT is to elevate your heartrate to 80-95 per cent of your maximum heart rate (MHR) for a short period followed by a moderate-intensity (50 per cent MHR) recovery period. You’ll know you’re working at a high intensity when you’re breathing hard and can’t speak. If you’re a numbers person, estimate your MHR by subtracting your age from 220. A 50-year-old’s MHR is roughly 170. Eighty to 95 per cent of that is 136 to 161 beats per minute.
There’s no precise protocol for a HITT workout. The high-intensity periods can be 20 to 30 seconds and the recovery periods can be up to 60 to 90 seconds or even longer. HIIT can include three to 10 rounds. The number of rounds and the length of active and recovery periods depend on your level of fitness. A beginner may choose to start with a 1:3 ratio, performing 20 seconds of high-intensity work and 60 seconds of recovery for three rounds. That’s a total of just four minutes, plus a five-minute warm-up and a five-minute cool-down period.
Because HIIT intervals are short, you can exercise at the upper end of your aerobic capacity, which would be impossible to maintain in an hour-long aerobics class or a marathon. A few minutes of HIIT is more effective for fat burning and lowering insulin resistance than steady-state exercise. Because HIIT is intense, your body uses more energy (calories) to repair itself in the 24-hour period afterwards, known as the after-burn. Therefore, your resting metabolism improves. HIIT can also improve your VO2 max, meaning it increases the amount of oxygen your body takes in while exercising. As your body adapts from multiple HIIT workouts over time, you’ll be in better shape for other activities as well.
Unlike steady-state aerobic exercise, you won’t lose muscle as a result of HIIT. When you run a marathon or perform other long, slower cardio exercise, your body enters a muscle-wasting catabolic state, using muscle for energy to keep going. HIIT workouts are anabolic – they maintain and can even help you gain muscle because they employ your fast-twitch muscle fibres in your thighs. Notice that marathoners tend to have less muscular legs than sprinters.
To get started, download a free HIIT timer app to your smartphone. When you’re exhausting yourself, you may not be able to focus on a watch or clock. Set the times and number of intervals on the HIIT timer and choose sound effects to prompt you. You can perform the timed intervals on a cardio machine such as a stationary bike, rowing machine or treadmill. You can also do HIIT by swimming, running outdoors or performing exercises such as burpees or jumping jacks that employ your large muscle groups.
Some fitness pros advocate giving up aerobic exercise in favour of HIIT. But, too much HIIT can stress the body and potentially put you into a chronic physiological fight-or-flight state, which is unhealthy. Doing the same kind of exercise week after week, whether it’s HIIT or aerobic exercise, can lead to repetitive use injuries or a plateau. Some experts believe that periodization is more effective; that is, a few weeks of HIIT then a few weeks of aerobics. Start with one HIIT workout per week and progress to no more than three to avoid over-training.
Always check with your medical doctor before starting a new exercise program. If you’re currently inactive, older or overweight, you may find HIIT unpleasant and too intense. Whatever your level of fitness, choose physical activities that you enjoy, that are safe and suitable for you, and that keep you challenged.