I made this post on another forum, and it’s one of those things I tend to write off-the-cuff that tends to summarize things fairly well, so I thought I’d share. The context was a discussion about ‘overtraining’ and stress/fatigue in general.
The long and short of it is simple. Your brain (specifically the hypothalamus and pituitary gland) regulates the overall status of your body based on several feedback signals – many are released during exercise (both at the “muscle” level and at the “central” level in the brain), but “life” stuff like work, lack of sleep, poor diet, etc, can all contribute to that overall “stress” signal.
In the short term this isn’t a problem; however, the fatigue response takes time to dissipate, depending on how “much” of a stress you were exposed to. In workout terms this can be excessive volume, intensity, or both.
A workout or two by itself is very rarely enough to cause any major disruption, unless it’s one hell of a workout. However stress is cumulative; if you don’t recover between workouts, it will build up from session to session. When that happens, the hypothalamus responds accordingly – mainly by throwing the HPA(drenal) axis out of whack. This is where the symptoms of reduced SNS activity start to show up – disrupted sleep, lack of motivation, elevated resting HR, all of that. It’s a case of chronically elevated stress hormones where the body has been briefly overwhelmed by the accumulated stresses. This is also very strongly associated with inflammation; in fact, one of the strongest signals of this stress-response condition is the variety of pro-inflammatory compounds that are released during exercise. In many ways it’s not unlike being sick – signals mediated from the brain and body alter your body’s condition and your behavior.
In the short term, we call this overreaching. You can get into this condition with just a few weeks of excessive training/under-recovery. The good news is that it tends to reverse itself fairly quickly once rest + diet is provided.
However if you keep this up for weeks and months on end, you get to the real overtraining syndrome (OTS) which is the one you have to really worry about. The good news is that few people that aren’t really hardcore endurance athletes will ever reach this state – and that’s a good thing, because it can require somewhat dramatic measures to recover from. Lifting weights 4-5 times a week and doing a few (cumulative) hours of cardio each week isn’t going to cut it.
Simply put, the stress of a workout creates a “fatigue” effect (what I just described). Too much fatigue accumulates and you get the hormonal disruption and inflammation of overreaching. Overreach for too long and you get overtrained.
Now, all that said, finding symptoms of “stress response” is not at all uncommon in females that diet to extremes. Why? Because lack of calories (and esp. carbs) combined with large amounts of exercise exacerbates this entire condition. Guess what most women dieters in general, to say nothing of those that want to step on stage, end up doing? Hours of cardio and 800 calories of lettuce and protein shakes. You may not be truly overtrained, but your body is basically in a state of chronic inflammation and elevated stress hormones. This can affect everything from muscle retention (overreaching/overtraining creates nearly pathological levels of protein loss from muscles) to fat loss.
This is where the whole “metabolic damage” thing comes into the equation. You haven’t actually damaged your metabolism; that’s not possible short of thyroid damage or screwing up something in the brain’s regulatory systems. What you have done is chronically knock the regulatory hormonal loops out of whack. As much as I hate the concept of “adrenal fatigue”, I do think that overreaching and a chronic stress response in general explain a lot of the symptomology. Too much exercise, not enough rest, not enough food, and not long enough recovery time allowed once the symptoms set in. If you’ve truly dug into your body’s reserves to a large degree, you may well need more than a 1-2 week quick-fix. You may have to wrap your head around a new way of doing things entirely.
In effect, that’s a long-winded way of saying “you have to take the good with the bad when you exercise, and short of resting more/eating more, there’s not much to be done about it”. Even the generally suggested restoration methods don’t do that much to help the process along (and a lot of evidence suggests that kind of thing may counterproductive in many ways to begin with).