With many people wanting to be healthy and physically fit, gyms around America are adopting a physical fitness program that according to experts is effective -- Interval training.

Interval Training is a kind of exercise in which a person alternates from an intense activity to a lighter one, repeating a number of times. HIIT sessions include extreme activities that increase heart rate in a short period of time and alternating with less extreme exercises to cool down. Many who are involved in the said training noted its effectiveness especially beneficial for the muscles and the heart. Experts agreed with their claims.

A study was conducted by Hakan Westerblad, physiology and pharmacology professor from the Karolinska Institute and his colleagues to prove this declaration. Muscle samples were collected from volunteers after alternately pedaling a stationary bike for 30 seconds at high intensity and cooling down for three minutes six times. Results explained how high intensity training works for the muscles.

Extreme exercises can stretch and break down channels in the muscle cells that control calcium. Cell signaling requires calcium. The intense demands provoked by the exercise cause the cell to adapt its energy production and turn to be more effective. Westerbled stated, "What we found was a breakdown of these channels that was totally unexpected. We have never seen anything similar. We saw a large production of free radicals, and these free radicals were specifically hitting the calcium channels.

Normal training also increases the amount of free radicals, but not by as much as interval training." Westerbled added, "The change in the channels triggered by the free radicals is the muscle cells' way of detecting and coping with the extreme duress caused by the high intensity exercise. During any physical training, the cell senses, 'I have a problem here. So to be better safe than sorry, they adapt so the next time they experience the intense exercise, the problem is lessened."

However, the effect of HIIT may vary for different athletes. The muscles of athletes who are immune to extreme work out do not react as much as how the recreational athletes' bodies respond to intense training. With the results of the study, those who are not long workouts devotee, may find interval training effective as a form of work out that can stretch and tone their muscles.