Monday, March 15, 2010

More efficient aerobic training by Jerry Brainum

Many bodybuilders avoid doing aerobics because they think it will cause them to lose muscle. There is some truth to this, since extended aerobic sessions lasting over an hour can increase cortisol levels. Cortisol is an adrenal stress hormone that induces catabolic or breakdown effects in muscle. On the other hand, aerobics is unsurpassed in promoting body fat losses, and in increasing muscular endurance. The question that arises then is how do you get the maximum benefits of aerobics without slipping into an overtraining or catabolic mode?
In recent years, it has become evident that one sure way around the aerobics dilemma is to do high intensity interval training (HIT). Several studies, mostly involving young college students, show that shorter, but more intense interval sessions provide similar benefits compared to the more conventional steady-state aerobics. Interval training involves alternate periods of high and low intensity within the same session. The higher intensity peaks are the key to what makes HIT so efficient. But one problem with this is that past studies used extremely high levels of exercise intensity, which many people, especially those who are out of shape, aren't capable of reaching.
A new study, however, shows that HIT doesn't have to be out of bounds for most people. The study involved seven men, average age, 21, who engaged in six training sessions over two weeks. Each session consisted on 8-12 bouts of riding a stationary bike at high intensity for only one minute, without another minute or so of rest. This level of exercise produced the equivalent of doing long, slow aerobics for 10 hours a week. Among the changes induced in the men during the study was an increase in oxidative enzymes needed to oxidize body fat, as well as increased muscle glycogen levels and levels of GLUT-4, a protein that transports glucose into muscle. This favors a more stable blood glucose level, and also offers preventive effects against the onset of diabetes. But the most interesting result of the study was a 56% increase in SIRT1. SIRT1 is thought to play a key role in promoting longevity. Many people spend oodles of money on high dose resveratrol supplements in the belief that resveratrol boosts SIRT1. In fact, recent studies show that resveratrol works by boosting another substance called AMPK, which is involved in fuel sensing in muscle. It may be that those spending a lot of cash on expensive resveratrol supplements may be better served if they got on a stationary bike and did some HIT.

Little, JP, et al. A practical model of low-volume high intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms.J Physiol 2010;588:1011-1022         

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