HIIT stands for high intensity interval training. This means very brief periods of really hard ‘all-out’ effort, followed by a rest or easy work period. The work-out should last from between 4 – 15 minutes, but no longer than 30minutes, and work to rest ratio will normally range from 1: 0.5 to 1:50. Because you are working at high intensities you are specifically working your fast twitch muscle fibres. These fast twitch muscle fibres are the muscles you recruit mainly for short, fast speed work, and having the rest periods in between these short bursts are essential for your muscle cells to recover their energy source. HIIT training however does not induce an increase in muscle size as with maximal effort weight training.
So what are the benefits of HIIT?
HIIT is more effective than the usual continuous medium-low intensity cardio training. HIIT burns more calories, plus you have greater calorie burning effects after exercise. This makes HIIT more effective for weight-loss and improving body composition, speeding up your metabolism throughout the day.
Research has found that more than 50% of people would prefer to do HIIT after engaging in this type of exercise compared to continuous moderate-low intensity training. Basically people get more of a high out HIIT post session, so are more likely to stick to doing this type of training.
Evidence from studies has shown the bodies adaptions to large volume endurance training, can be brought about a lot quicker with a surprisingly smaller volume of HIIT. Explained more simply this means your body can get fitter, quicker by spending much less time exercising each week, by means of HIIT. Experiments in labs, using previously sedentary individuals (those that don’t take part in regular exercise) showed improvements in endurance fitness after only 6 HIIT sessions, of 2-3 minutes of work over a 2 week period.
HIIT training is also used by athletes who are already of a high fitness level to further their fitness, generally by increasing stroke volume of their heart (the amount of blood you heart can pump in one heart beat). HIIT also reduces risk of cardiovascular disease, and has been shown to be a safe from of exercise for those already with cardiovascular disease.
High intensity interval training doesn’t just have to be in the form of running, it can be cycling, swimming, rowing, burpees, weight- based exercises (even tyre flipping!), or a combination, as long as it involves ‘all-out’ effort. An example would be 30 seconds of ‘all-out’ cycling followed by a 1 minute slow pace cycle, or Tabata method on the rowing machine i.e. 20 seconds of hard work followed by a 10 second rest, repeated 8 times.
As you saw above, the work to rest ratio can vary greatly, and the ratio you use will depend on your sport or whether you are doing HIIT for general fitness. Those taking part in sports involving very short, rapid periods of maximal strength, such as powerlifting, would want to interval train at a work to rest ratio of 1:50-1:35. Those taking part in sports which involve varied intensities, with minimal rest, such as football, should be training in the ratio of 1:4-1:0.5. For general fitness, you could vary the ratio from 1:5-1:1.
It is thought that there is a minimum amount of sessions you need to be doing in order to see rapid changes. A good start and something which can be easily slotted into you routine is 1-3 minutes per training session of high intensity work, 3 times a week.
I hope you have found this an interesting subject, HIIT seems to be taking the fitness industry by storm and clearly rightly so! Any questions, or if you are interested in personal training to get you on the correct tracks, let me know. I will get back to you as soon as I can!