'This type of training is very demanding and requires a high level of motivation. However less frequent, higher intensity exercise can indeed lead to improvements in health and fitness.'

"Short bouts of very intense exercise improved muscle health and performance comparable to several weeks of traditional endurance training," says Martin Gibala, an associate professor in the department of kinesiology of McMaster University and leader of the provocative new study.

Performing repeated bouts of high-intensity sprint-type exercise resulted in profound changes in skeletal muscle and endurance capacity, similar to training that requires hours of exercise each week, the researchers report in the June edition of the Journal of Applied Physiology.

Endurance Capacity Increased

The study was conducted on 16 subjects: eight who performed a two-week sprint interval training program and eight who did no exercise training. The training program consisted of between four and seven 30-second bursts of "all out" cycling followed by four minutes of recovery three times a week for two weeks.

Endurance capacity in the sprint group increased on average from 26 minutes to 51 minutes, the researchers found, whereas the control group showed no change.

The muscles of the trained group also showed a significant increase in citrate synthase, an enzyme that is indicative of the tissue's ability to utilize oxygen.

High Level of Motivation

"Sprint training may offer an option for individuals who cite "lack of time" as a major impediment to fitness and conditioning," said Gibala.

"This type of training is very demanding and requires a high level of motivation," he noted. "However less frequent, higher intensity exercise can indeed lead to improvements in health and fitness."