High-intensity interval exercise is characterized by relatively brief, intermittent periods of muscle contraction, often performed with an ‘‘all-out’’ effort or at an intensity close to that which elicits peak oxygen uptake. Depending on the specific intensity, a single effort may last from a few seconds to up to several minutes, with multiple efforts separated by up to a few minutes of rest or low-intensity exercise for recovery. Although sometimes equated with strength or heavy resistance training, high-intensity interval exercise training (HIT) does not induce marked fibre hypertrophy (Ross and Leveritt 2001). Rather, there is a growing appreciation of the potential for HIT to timulate the skeletal muscle remodeling normally associated with traditional endurance training (Gibala and McGee 2008).
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Like strength or resistance training, interval exercise is characterized by brief intermittent bouts of relatively intense muscle contraction. However, interval exercise training induces phenotypic changes that resemble those elicited after traditional endurance training.