IT is the fitness trend that has taken over gyms as the image-obsessed seek out better, faster ways to shed unwanted body fat, but now its benefits are being called into question as injuries are on the rise. High Intensity Interval Training (HIIT) has been the buzzword over the past few years and involves exercising intensely for multiple short bursts with small rest breaks in between.

But a recent study by the University of Bath found that low-intensity exercise can be just as effective as HIIT for weight loss. They asked people of a similar age to exercise five times a week at different intensities – with half the group working out intensely and the other half, moderately. After a three-week period, both groups had lost the same amount of weight.

Sunday Herald fitness columnist, sports physiotherapist Jonny Kilpatrick is one of the fitness experts who is calling for caution when it comes to exercising in this furious stop-start way. He reports a rise in the number of injuries he sees in his clinic related to the HIIT trend, with people being encouraged to push themselves to their limits and incurring injuries.

Kilpatrick says: “While there is no doubt that HIIT can rapidly increase fitness and provide health benefits associated with exercise, there are also a number of pitfalls to training exclusively like this. HIIT-type session exercises are often performed quickly in order to set a time or score, which requires pushing into fatigue using weights or load that can often be disproportionately high for your current strength levels and abilities. This can cause soft tissues and joints to become overloaded and injured.”

He warns that training to this intensity five or six days a week is unsustainable, unproductive and can lead to injury.

Dr Niels Vollaard, lecturer in exercise physiology at the University of Stirling also sounds a note of warning about overdoing HIIT.

“The research on HIIT has been based on cycling, combining easy peddling and sprints. Because the motion is cyclical and low impact, it’s a safe way to exercise,” he says. “If you take up HIIT by doing circuit classes that include running and lifting weights and you are not very fit, you might well end up injured. Running can lead to injury because of all that pounding, and resistance training is good for muscle building, but not great for cardiovascular fitness. Any exercise that stresses the joints, ligaments and tendons, can lead to injury, particularly if you are overweight. Muscles can repair themselves easily but not much blood goes to ligaments and tendons and these repair much more slowly.”

Dr Vollaard advises that HIIT, while good for improving overall fitness, is not a particularly effective way to lose weight and that an hour-long walk and eating less is an easier way to shed the pounds. But, he stresses that becoming fitter is more important to health than losing weight and proposes a new way of attaining fitness. He is researching the effectiveness of doing 10 minutes of low intensity cycling interspersed with two 20-second sprints three times a week on a special stationary bike called a High Octane Ride, which can go up to much higher speeds than static gym bikes or road bikes.

“The research is not complete but we are getting encouraging results. I would like to see these bikes at workplaces and in shopping malls and doctors’ surgeries. People can hop on and off them and don’t need to shower afterwards or wear special gym gear. It’s a very time-efficient way to exercise and would fit easily into busy lives and offer the same health benefits as going to HIIT or long, low-intensity exercise sessions.

“Whatever exercise you do, it’s important to vary it and include elements of cardiovascular, resistance training along with balance and core strengthening. If you are unfit or overweight, build up gradually. Being fit protects against lifestyle illnesses such as heart disease, strokes and diabetes, particularly as we age.”