Now before getting into the details, notice that I didn’t say HIIT would be easier, just that it would take less of your time. In fact, the HIIT approach to cardio exercise is very physically demanding and isn’t for everyone. If you have any cardiovascular problems or other health concerns that limit your ability to exercise at very intense levels, or if you are relatively new to aerobic exercise or not already in good shape, HIIT is not for you—at least for now. If you have any doubts or concerns about whether it might be safe for you, check in with your medical professional before trying HIIT.
What It Is and How It Works
HIIT is a specialized form of interval training that involves short intervals of maximum intensity
exercise separated by longer intervals of low to moderate intensity exercise. Because it involves briefly pushing yourself beyond the upper end of your aerobic exercise zone, it offers you several advantages that traditional steady-state exercise (where you keep your heart rate within your aerobic zone) can’t provide:
- HIIT trains and conditions both your anaerobic and aerobic energy systems. You train your anaerobic system with brief, all-out efforts, like when you have to push to make it up a hill or sprint the last few hundred yards of a distance race.
- HIIT increases the amount of calories you burn during your exercise session and afterward because it increases the length of time it takes your body to recover from each exercise session.
- HIIT causes metabolic adaptations that enable you to use more fat as fuel under a variety of conditions. This will improve your athletic endurance as well as your fat-burning potential.
- HIIT appears to limit muscle loss that can occur with weight loss, in comparison to traditional steady-state cardio exercise of longer duration.
- To get the benefits HIIT, you need to push yourself past the upper end of your aerobic zone and allow your body to replenish your anaerobic energy system during the recovery intervals.
General HIIT Guidelines
- HIIT is designed for people whose primary concerns are boosting overall cardiovascular fitness, endurance, and fat loss, without losing the muscle mass they already have.
- Before starting any HIIT program, you should be able to exercise for at least 20-30 minutes at 70-85% of your estimated maximum heart rate, without exhausting yourself or having problems.
- Because HIIT is physically demanding, it’s important to gradually build up your training program so that you don’t overdo it. (The sample training schedule below will safely introduce you to HIIT over a period of eight weeks.)
- Always warm up and cool down for at least five minutes before and after each HIIT session.
- Work as hard as you can during the high intensity intervals, until you feel the burning sensation in your muscles indicating that you have entered your anaerobic zone. Elite athletes can usually sustain maximum intensity exercise for three to five minutes before they have to slow down and recover, so don’t expect to work longer than that.
- Full recovery takes about four minutes for everyone, but you can shorten the recovery intervals if your high intensity intervals are also shorter and don’t completely exhaust your anaerobic energy system.
- If you experience any chest pain or breathing difficulties during your HIIT workout, cool down immediately. (Don't just stop or else blood can pool in your extremities and lightheadedness or faintness can occur.)
- If your heart rate does not drop back down to about 70% of your max during recovery intervals, you may need to shorten your work intervals and/or lengthen your recovery intervals.
- HIIT (including the sample program below) is not for beginner exercisers or people with cardiovascular problems or risk factors. If you have cardiovascular problems or risk factors should NOT attempt HIIT unless your doctor has specifically cleared you for this kind of exercise.
The key element of HIIT that makes it different from other forms of interval training is that the high intensity intervals involve maximum effort, not simply a higher heart rate. There are many different approaches to HIIT, each involving different numbers of high and low intensity intervals, different levels of intensity during the low intensity intervals, different lengths of time for each interval, and different numbers of training sessions per week. For example, a good starter workout is running as fast as you can for 1 minute and then walking for 2 minutes. Repeat that 3-minute interval five times for a 15-minute, fat-blasting workout! It sounds too simple to be effective, but science doesn't stretch the truth.
You don’t need to swap all of your aerobic exercise for HIIT to gain the benefits. A good balance, for example, might be two sessions of HIIT per week, along with 1-2 sessions of steady-state aerobic exercise. As usual, moderation is the key to long-term success, so challenge yourself—but don’t drive yourself into the ground. And most importantly, get ready to see major changes in your body and your fitness level!
