Purpose: The purpose of this study was to determine the effectiveness of brief intense interval training as exercise intervention for promoting health and to evaluate potential benefits about common interventions, that is, prolonged exercise and strength training.
Methods: Thirty-six untrained men were divided into groups that completed 12 wk of intense interval running (INT; total training time 40 min·wk−1), prolonged running (∼150 min·wk−1), and strength training (∼150 min·wk−1) or continued their habitual lifestyle without participation in physical training.
Results: The improvement in cardiorespiratory fitness was superior in the INT (14% ± 2% increase in V˙O2max) compared with the other two exercise interventions (7% ± 2% and 3% ± 2% increases). The blood glucose concentration 2 h after oral ingestion of 75 g of glucose was lowered to a similar extent after training in the INT (from 6.1 ± 0.6 to 5.1 ± 0.4 mM, P < 0.05) and the prolonged running group (from 5.6 ± 1.5 to 4.9 ± 1.1 mM, P < 0.05). In contrast, INT was less efficient than prolonged running for lowering the subjects' resting HR, fat percentage, and reducing the ratio between total and HDL plasma cholesterol. Furthermore, total bone mass and lean body mass remained unchanged in the INT group, whereas both these parameters were increased by the strength-training intervention.
Conclusions: INT for 12 wk is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, but in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training. Furthermore and in contrast to strength training, 12 wk of INT had no impact on muscle mass or indices of skeletal health.