High intensity interval training 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. It can be used effectively in all three disciplines of triathlon training – swimming, cycling, and running.
To get the benefits from 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.
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.
The purpose of HIIT is to increase the amount of time you spend exercising at very high intensities.
Let’s take an example: your best 5K race time is 27:30 (5:30min/km). If you could improve your ability to hold a pace that was faster by 15 seconds per kilometre, you’d need to run at 5:15min/km pace, which would require a 25% increase of pace.
The HIIT approach is designed to work you at that higher intensity in short bursts, with short recovery periods to increase the effectiveness of your training. Improving the quality of your sessions means you need to be increasing the time spent above lactate threshold. Training at intensities above 90% VO2max is one of the most potent routes to fitness. Controlled interval sets allows you to enter your 'red-line' training zone productively.
But you must work as hard as you can during the high intensity intervals, until you feel the burning sensation in your muscles, and the I-am-going-to-vomit feeling in your chest, that indicates 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. You may need to experiment with this a bit. Just keep in mind that if you are trying to improve your lactate threshold then try to keep recovery intervals short.
A simple and effective method to get started with HIIT is to match the recovery time to the effort time and then try to shorten the recovery. Every second counts, so use a stopwatch or better still HRM/computer to monitor every rep. If your need longer recovery than your effort times, you need to reduce your pace in the efforts a little. Alternatively, you could do less repetitions and work towards building up more reps over time.
High-intensity training can be tricky to manage. Follows these 3 tips to ensure your HIIT is beneficial:
- Don’t make all workouts HIIT
- Do plan your HIIT sessions deliberately. These do not need to be very long sessions, so are ideal for before work
- HIIT also needs appropriate recovery. The next session the following day needs to be a recovery session such as a swim, endurance ride, or a rest day. Use common sense
- Do everything you can to ensure good form so get a bike fit, use a coach, etc