In the last few years, the health and fitness industry has seen the emergence of a number of shorter, results-driven workout concepts for ‘time poor’ consumers. Women-only franchises Curves and Vivafit have offered a 30-minute, circuit-based workout for some time, but are now being joined by the likes of Fit n Fast in Australia, where Quickie workouts are available in activities such as cycling, boxing and circuits – and where the intensity is being ramped up to challenge a younger demographic.

From a fitness equipment supplier perspective, milon’s eccentric and concentric resistance equipment has been designed to maximise results via a circuit workout that takes around 30 minutes. Power Plate also recently demonstrated a 20-minute concept which combines its vibration training platform with its new powerBIKE with vibrating pedals. Classes are getting shorter.

An elite heritage
They’re also getting tougher. Because what this is all leading to is the emergence of HIT (high-intensity interval training). Or should we say re-emergence? After all, in essence HIT is a training method that’s been around for many years in the elite sports arena.

Interval training in its modern form dates back to the 1930s, when Woldemar Gerschler (Germany) and Gosta Holmer (Sweden) used it to enhance the performance of their national teams. And in Finland, Lauri Pikhala was creating interval training programmes for runner Paavo Nurmi back in 1910.

Holmer dubbed the approach fartlek – Swedish for ‘speed play’ – thanks to the use of ‘faster than race’ pace. Concentrating on simultaneous speed/endurance training, the training protocol puts stress on both aerobic and anaerobic energy systems due to the alternating pace and intensity of the exercise. It’s now used the world over to offer variation in an elite athlete’s preparation throughout the year. And now it’s coming to fitness centres and gyms in the form of HIT. So how do we define HIT?

Defining HIT
Len Kravitz and Lance Dalleck – researchers at the University of New Mexico, in the US – define interval training as “high-intensity, short duration training sessions performed at workloads above the lactate threshold, marked by an abrupt increase in blood lactate that forces the muscle to revert from aerobic to anaerobic metabolism”.

Clearly this is hard to measure within a gym environment. However, in a review paper undertaken in February by New Zealand’s AUT University (see the Literature Review panel), HIT is defined as either working at over 75 per cent of heart rate maximum (HR max) or 75 per cent of maximum oxygen uptake (VO2 max), followed by rest periods.

Intervals vary from 1:1 (work:rest) ratios, to 2:1 or other variations depending on fitness levels. The rest phase can either be complete rest or dropping back to a moderate intensity to enable recovery.

“However, 75 per cent HR max and 75 per cent VO2 max are very different intensities and not to be confused as being the same,” stresses Randy Huntington, global director of marketing, performance, education and research at fitness equipment specialist Keiser. So there are no clear-cut guidelines as yet, other than that the work phases should be ‘hard’ or ‘very hard’.

Huntington, meanwhile, categorises HIT as a form of circuit training. “In 1953, RE Morgan and GT Anderson at the University of Leeds [UK] created circuit training – of which interval training is a subset – with Manfred Scholich going on to write the bible on interval/circuit training in 1986,” he explains. “There are many ways to do circuits and Scholich has already labelled them quite well, setting a series of criteria: sets, repetitions, load, type of exercise, order of exercises, number of exercises, rest interval, work interval and density.

“It’s important that a common vocabulary be established within the fitness industry, otherwise we’ll end up with fancy marketing names for programmes that have actually existed for over 40 years – and in some cases, where the roots are over 100 years old.”

Benefits of HIT
But if precise terminology and parameters are still to be decided, there does seem to be broad agreement on the benefits of HIT.

“Research shows that HIT delivers results that surpass conventional, steady-state training,” says Bryce Hastings, technical consultant for group exercise company Les Mills International (see sb08/3 p100). “These include accelerated aerobic conditioning, getting you fitter faster; an improved anaerobic threshold, letting you go harder for longer; improved insulin resistance and growth hormone changes, with enhanced hormonal responses; and the generation of athletic, powerful muscle, giving you the tone you dream about.”

Huntington adds: “Interval training has the potential to burn more calories than conventional aerobic/strength training and is an effective means of improving strength/muscular endurance. In addition, it has always delivered faster results. However, all this is at the potential expense of injury and endocrine burnout. It takes a while to adapt to such workouts, and in most cases adherence is less time than the required time to adaptation. If we’re to bring it into the gym, we need to make it fun so people will continue to do it, thereby gaining a cumulative effect.”

There’s also an argument that a HIT circuit may not deliver optimum results. Huntington continues: “In the late 80s and early 90s, Keiser developed the XPress Circuit for time-conscious, non-elite members. This was done in the full knowledge that circuit training will always compromise the true effectiveness of the five S’s – strength, speed, skill, stamina, suppleness – when they’re not done as discreet parts of a programme. Does this make HIT or circuit training bad? Absolutely not. It just means that the best results you can get will be less than the best result you could achieve by focusing on any one of the five S’s individually.”

For non-elite athletes, however, the benefits will already be very compelling. Not only that, but the AUT University/Les Mills review paper highlights benefits for a far more diverse range of exercisers than might have been expected. Gym-based use of HIT could, it seems, have a broad appeal.