Higher mitochondrial fatty acid oxidation following intermittent versus continuous endurance exercise training

It has been well documented that skeletal muscle fatty acid oxidation can b e elevated by continuous endurance exercise training. However, it remains q uestionable whether similar adaptations can be induced with intermittent in terval exercise training. This study was undertaken to directly compare the rates of fatty acid oxidation in isolated subsarcolemmal (SS) and intermyo fibrillar (IMF) mitochondria following these different exercise training re gimes. Mitochondria were isolated from the gastrocnemius-plantaris muscles of male Sprague-Dawley rats following exercise training 6 days per week for 12 weeks. Exercise training consisted of either continuous, submaximal, en durance treadmill running (n = 10) or intermittent, high intensity, interva l running (n = 10). Both modes of training enhanced the oxidation of palmit yl-carnitine-malate in both mitochondrial populations (p < 0.05). However, the increase associated with the intermittent, high intensity exercise trai ning was significantly greater than that achieved with the continuous exerc ise training (p < 0.05). Also, the increases associated with the IMF mitoch ondria were greater than the SS mitochondria (p < 0.05). These data suggest that high intensity, intermittent interval exercise training is more effec tive for stimulation of fatty acid oxidation than continuous submaximal exe rcise training and that this adaptation occurs preferentially within IMF mi tochondria.