The signs and symptoms of overtraining differ between aerobic and anaerobic exercise. People who overtrain while engaged in endurance or aerobic activity often exhibit such symptoms as sleep difficulties, higher resting pulse levels upon arising, adverse mood changes, and lack of training enthusiasm. The signs of overtraining that occur with anaerobic, high-intensity exercise, exemplified by bodybuilding training, are more subtle. These can include lack of muscular progress, increased injury rates, loss of strength, and possibly even a loss of muscle size.
Past studies indicated that one way to monitor such overtraining effects involves measuring hormone levels. Since overtraining often induces a catabolic state, due to increased secretion of cortisol (an adrenal stress hormone), cortisol levels are expected to increase under overtraining conditions. Cortisol has an inverse relationship with other anabolic hormones, such as testosterone, growth hormone, and insulin. Thus, when cortisol levels are elevated, these anabolic hormone levels usually decline.
But recent studies that examined these hormonal effects of overtraining found that many of the expected hormonal changes thought to occur with overtraining just don’t happen--despite clear signs of overtraining. An example of this is a new study reported in the Journal of Applied Physiology 1998;85:2352-2359. This study monitored 2 groups of experienced weight-trained men. One group engaged in overtraining by training daily for 2 weeks using resistance equal to 100% of maximum for one repetition. The other group trained just once a week, using poundages equal to 50% of one-repetition maximum.
The overtraining group overtrained only their legs, which led to a significant decrease in leg strength after 2 weeks of such training. The overtraining was severe enough to lead to an inability to train with their normal weights for 8 weeks following the study. Interestingly, a muscle enzyme that often increases with muscle damage (creatine kinase) did not increase in the overtrained men, nor did they experience any extensive muscular soreness. Thus, these two usual indicators of overtraining and incomplete muscular recovery didn’t apply to this group.
While overtraining usually leads to a drop in total testosterone levels both during rest and after exercise, the men engaged in overtraining in this study showed no changes in pre-exercise levels of testosterone, and showed slightly increased levels after exercise. This increased level of testosterone was thought to be due to the increased secretion of epinephrine and norepinephrine exhibited by the overtraining group.
Overtraining often leads to a blunting of free or active testosterone levels, often due to a concomitant release of cortisol. But the overtrained men in this study showed no changes in free testosterone, which increased after training as it normally does (without overtraining). Free testosterone represents the 1% of testosterone in the body that isn’t bound to circulating proteins such as sex-hormone binding globulin (SHBG) or albumin. Only the free version can interact with cellular receptors and initiate anabolic responses in muscle.
Regarding cortisol, the overtraining group showed no pre-exercise changes in the hormone, but did show decreased secretion after exercise. The study authors suggest that the training sessions may have been too brief to elicit a full cortisol response. However, ACTH, a pituitary gland hormone that controls cortisol release from the adrenal gland cortex, also showed no changes in the overtrained group. Lowered cortisol levels are a common finding with experienced weight-training athletes. The theory is that the body gradually accommodates to the increased stress of exercise by modulating adrenal gland activity.
Likewise, the usual testosterone to cortisol ratio, often changed in favor of cortisol in overtrained endurance athletes, didn’t occur in this overtrained weight-training group. The study authors note that this makes the testosterone to cortisol ratio a poor indicator of training recovery for high intensity weight-training.
Several articles have stated that overtraining blunts growth hormone release. But it didn’t have any effect on GH secretion or release in this study. This differs from reports of a recent study (Medicine and Science in Sports and Exercise 1998;30:407-414) that did find a decreased GH release during high intensity overtraining in endurance athletes. Obviously, weight-training somehow affects the release of GH in an manner different from that of aerobic training, even when both are done under high intensity conditions.
Since the usual markers of overtraining don’t appear to exist in people engaged in high intensity resistance overtraining, the study authors suggest that other areas be monitored to prevent overtraining onset. These include measuring sympathetic hormone response (epinephrine and norepinephrine) and changes in neuromuscular activity, i.e., loss of muscle size and strength.
One notable flaw of this study, however, was the relatively short duration of the workouts used to produce the overtraining effect. Even the study authors admit that this low volume of exercise may not be enough to make inroads into the hormonal responses that occur with more extensive overtraining. Also, what happens when a person uses a high intensity weight-training program combined with aerobic exercise every day? This is a common practice with competitive bodybuilders, who do the aerobics for purposes of body composition changes (fat loss).
How does diet and nutrition enter into this overtraining picture? Will using supplements touted to increase testosterone or control cortisol help to alleviate overtraining and increase muscular recovery? These are all valid questions that are open to future research.
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
