Keeping fit or becoming fitter by regular exercise is important if you want to stay healthy. The usual advice is to perform at least 150 min of exercise a week, but could shorter, more intense workouts be just as good or even better? This is an important question, as for most people lack of time is a real issue.
Competitive athletes of all levels use interval training, -together with continuous workouts-, as it improves their fitness more and quicker than continuous endurance exercise. It is also less time consuming. Interval training sessions consists of bursts of intense exercise (e.g. 3 to 5 min at 85 to 90% of your maximal heart rate) followed by short periods of easy exercise.
Low volume, high intensity interval training or HIIT takes the idea of saving time a step further. It consists of 3 or 4 bursts of 30 sec “all out” exercise at your absolute maximum, with about 4 min of easy exercise after each burst. This session is typically repeated 3 times a week. Even though each HIIT session is preceded by a thorough warming-up and followed by a cooling down, it would typically take only about 3 x 25 to 30 min = 75 to 90 min a week, and it could therefore be a solution for sedentary people who are short of time.
However, there is a problem: going all out for 30 sec is much harder than you imagine. In labs, volunteers usually require plenty of encouragement and most of them feel nauseous or light headed. Moreover, it is likely to put you at a higher risk of injuries, and it is not sure yet if it is safe for people with health problems. Scientists have therefore wondered if a longer exercise burst at a slightly lower intensity would be easier to manage.
Low volume HIIT sessions are usually performed in labs, using specialised material. It is therefore not clear yet if these sessions could also be done without equipment, e.g. by running in your local park.
Helen Lunt and her colleagues have investigated just that, and published their results in January 2014.
49 previously sedentary volunteers were divided in 3 groups. One group, called “walk”, performed 30 minutes of continuous endurance exercise by walking. Another group, “ait” undertook an interval training session by jogging or running for 4 minutes at 85- 95% of their maximal heart rate followed by 3 minutes of easy walking. They repeated this 4 times per session. The last group, “mvit”, ran all-out for 30 sec up a slope at maximal volitional intensity, followed by a 4 min of easy walking. They started off by doing this exercise burst 3 times, and tried to increase the number of repetitions per session. All the participants warmed up before their workout and cooled down afterwards, and performed 3 workouts a week. All the sessions were hold at a public park and supervised by the researchers. The aim was to keep going for 12 week and to compare the VO2max of the participants before and after this period. VO2max is a measure of your aerobic fitness, and higher values are indeed linked to better health and longevity, even in overweight or obese people.
Unfortunately, 1 participant of the walk group, 3 of the ait and 4 of the mvit group had to drop out because of injuries related to the exercise.
At the end of the 12 weeks, the ait group had improved their VO2max more than the walk and mvit groups. The walk group had experienced the least adverse effects, as only one the participants had to stop.
The researchers concluded that interval training can help you to improve your fitness without spending as much time as you would if you performed continuous endurance training, but it comes at a price: your risk of being injured is greater. The results of the mvit group were disappointing, but this might be due to the fact that so many of them dropped out. Moreover, the time gained was not that important: in practice the walk group ended up by working out for 116 min week, the ait group 74 min and the mvit 46 min.
Could interval training help me if I’m sedentary?
Interval training can indeed improve your fitness quicker than continuous training, but it comes at a price: it is much harder work. Moreover, it might not be safe for people with health problems, and you should therefore first check with your doctor to see if it is ok for you. As it is hard work, it is better to do it under supervision by a fitness professional, who can make sure that you work out at the right level and who will encourage you.
Is low volume HIIT useful even if I’m used to training?
Most athletes are reluctant to change a training schedule that works, and there are therefore not many studies evaluating low volume HIIT. Moreover, as they do many different sessions, it is difficult to find out if improvements are due to the low volume HIIT or to another part of their training schedule.
If you are a competitive athlete, you are probably used to interval training. A proper low volume HIIT session however, is very hard, and might be too hard to do without continuous verbal encouragement from your coach. As always, everybody is different, and you have to find out what is best for you.
Disclaimer: this article is for general information only, and does not replace professional advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.
A P Bacon, R E Carter, E A Ogle et al. VO2max trainability and high intensity interval training in humans: a meta-analysis. PlosOne. 2013; doi 10.1371/journal pone.0073182
M J Gibala, J P Little , M J MacDonald et al. Physiological adaptations to low-volume, high-intensity interval training in health and disease. J Physiol. 2012; 590(Pt5): 1077-1084.
H Lunt, N Draper, H C Marshall et all. High intensity interval training in a real world setting: a randomized controlled feasibility study in overweight inactive adults, measuring change in maximal oxygen uptake. PLoSOne. 2014; 9(1): e83256.