It may seem too good to be true, but short bursts of high-intensity exercise really may have more health benefits than longer, but less intense training sessions.
What is HIIT?
Put simply, it uses timed periods of very intense exercise interspersed with a less intense recovery period. It's most often performed in the form of cardiovascular exercise – running, cycling, circuit-style burpees (squat
thrusts) – but it can be appropriate for resistance work using body weight, or free weights. Very often classes and coaches will combine the two in HIIT circuit sessions.
If you want to get technical, HIIT is defined as several bouts of high-intensity exercise carried out at between 85 to 95 per cent of maximum heart rate and/or VO2MAX (peak oxygen uptake) – lasting between one to four minutes – interspersed with intervals of rest or active recovery. i
How to do a HIIT session
The total time for a session is typically less than 30 minutes, ii with short intervals of between 15 and 60 seconds, and longer intervals of between one and four minutes.
A two-to-one ratio of work to recovery periods is a popular protocol, where you spend double the amount of time at high intensity to your low intensity recovery periods. So, for example, if you were doing HIIT by running, you
might sprint for 40 seconds and recover for 20 seconds for a set number of intervals. Working at 85 to 95 per cent of max heart rate is hard work. You won't be able to talk and will feel you can only keep going for short periods.
Health benefits of HIIT training
• It's a fat burner: In 1994 Canadian researchers found iii that whilst those who exercise moderately burn twice as many calories as those who follow a HIIT programme, the higher intensity group burnt more subcutaneous fat. Other studies have found it burns more abdominal fat. iv
• It's good for the heart: Just like easier, more time consuming continuous moderate exercise (CME), such as a long walk, HIIT benefits your heart health. A 2012 report that reviewed studies looking at the impact of HIIT on those with coronary artery disease (CAD) and heart failure (HF) undergoing cardiac rehabilitation, revealed HIIT appeared safe and better tolerated by these patients than CME. v
• Helps control blood pressure: Researchers have found HITT may be better for blood pressure than moderate exercise, as it can influence many factors linked to high blood pressure, including stiffness of the arteries – one of the contributory factors to better aerobic fitness. vi
• Other benefits: HITT boosts aerobic and anaerobic fitness vii and improves insulin sensitivity. viii
Where can you do HIIT?
A combination of great research to back up the health and fat-burning claims, and demands from time-poor clients, means that HIIT has become a feature on most health club timetables. It forms the basis of workouts such as TABATA,ix a Japanese take on HIIT, and LES MILS GRIT™ classes, x as well as inspiring the rise of Cross Fit – a circuit style workout. xi
HITT is also a core element of many group boot-camp training classes carried out in parks and fitness studios across the country.
Fuel for HIIT
High-intensity training will tap into your energy reserves, so if you're regularly pushing yourself to the limits, it's worth focussing on nutrition and ensuring you're eating plenty of good quality protein, wholegrains and fresh fruit and vegetables – as well as staying hydrated all day long.
Supplements for energy and recovery
If you're going to do a hard HIIT circuit session, consider taking a caffeine-based supplement before you start. Co-enzyme Q10 supplements and ginseng may also give you an energy boost.
Don't forget to pay attention to recovery – rest and recovery are all-important when it comes to sustaining energy and boosting performance and there are a number of supplements that can help including magnesium, (HMB) and cherry extract.