High-intensity interval training (HIIT) has become popular with athletes and amateurs and has clear visible benefits.

But sports scientists have always struggled to understand how a short amount of activity can produce similar effects as endurance training.

Now, researchers at the Karonlinska Institute in Sweden have found that even small levels of intensive exercise boost the production of mitochondria – the cell's batteries – which enhance muscle endurance.

Volunteers who cycled for 30 seconds as fast as possible, six times, triggered the effect, suggesting just a few minutes is all it takes for results to begin to show. Tissue samples of their muscles showed benefits.

"Our study shows that three minutes of high-intensity exercise breaks down calcium channels in the muscle cells," says Professor Hakan Westerblad, principal investigator at Karolinska Institutet's Department of Physiology and Pharmacology.

"This causes a lasting change in how the cells handle calcium, and is an excellent signal for adaptation, such as the formation of new mitochondria."

Mitochondria are like the cell's power plants, and changes that stimulate the formation of new mitochondria increase muscle endurance.

However the researchers also found that anti-oxidants like vitamin E and C can stop the effect.

"Our study shows that antioxidants remove the effect on the calcium channels, which might explain why they can weaken muscular response to training," added Professor Westerblad.

The study was published in the journal PNAS.

The Telegraph, London