Training is only the initial stimulus for your body to undergo physical change. You build muscle, burn fat, and alter your physical appearance via all of the metabolic, hormonal, and physiological processes that take place in between training sessions. If you train too frequently and short circuit the recovery process, you will not see visual improvements no matter how hard you train.
Inadequate recovery equals no adaptive response. This equals no muscle growth, no metabolic boost, no burning off body fat, and no change in physical appearance. In the worst-case scenario, it can actually make you more prone to storing body fat, due to chronically elevated levels of the hormone cortisol. You might as well just sit at home eating (insert your favorite junk food), and watching (insert your favorite junk TV show). At least that is a fun way to get fat; trust me I've done it.
Here are just a few of the physiological processes that happen in the recovery phase from a weight training session Satellite cells are activated when muscle fibers receive trauma or damage. Satellite cells fuse to existing muscle fibers and help to repair/regenerate the damage by increasing the size and number of contractile proteins (called actin & myosin) within those fibers. The body restores cell fluids, electrolytes, and minerals lost during training. The body must refill muscle glycogen stores as glycogen is the primary fuel used during high intensity training. Contrary to supplement marketing, this doesn't just happen with a single high-carb post-workout shake. It takes multiple balanced meals to adequately restore glycogen levels. The immune system responds with a sequence of actions leading to inflammation. This inflammation is what causes muscle soreness. The purpose of this inflammation is to contain the damage within the muscle cells, increase blood flow and nutrient delivery to the damaged area, repair the damage, and clean up the injured area of waste products. Antioxidants scavenge free radicals and repair oxidative stress caused by the increased rate of oxygen consumption during the training session. Growth factors (such as IGF-1) regulate insulin metabolism and stimulate protein synthesis. Testosterone, cortisol, and growth hormone levels rise, fall, and return to baseline levels in their own respective patterns (assuming you are training naturally without performance enhancing drugs). All of the above processes can take up to 48 hours under normal circumstances but can be delayed by many factors including poor dietary decisions, lack of sleep, and high stress levels just to name a few. On a side note, all of the above actions require energy (calories). This is why we say that strength training boosts the metabolism (the rate at which your body burns calories on a daily basis) and is so crucial to the body composition change process.
Here is the take home message: Recovery is a complex process, and the advanced trainee trying to maximize their results must balance intense training with recovery. Of course if you train like a wimp, you can train every day, because you have nothing to recover from. I'm really just speaking to the athletes who make a sincere effort to bust their butts in the gym in order to change their bodies.
Overtraining Syndrome The frequency recommendations at the beginning of this article were set for a reason. They were not just blindly pulled out of a hat. And remember, these recommendations are for people training primarily for physique development. I understand that participation in competitive sports may require more frequent and longer training sessions to maximize sport performance and/or adhere to competitive schedules. But that's also why competitive sports have off-seasons.
What happens if you train more often than you can recover from? There is an actual technical term for the physiological state that results from training too long or too frequently on a regular basis: Overtraining Syndrome. According to the NSCA Overtraining Syndrome is "Excessive frequency, volume, or intensity of training that results in extreme fatigue, illness, or injury which is often due to a lack of sufficient rest, recovery, and perhaps nutrient intake."
And what are some of the effects of this overtraining syndrome? Here you go Emotional and mood disturbances including increased irritability, anxiety, and even depression-like symptoms. Sleep disturbances. Altered immune system functioning including increased rates and duration of illnesses and infections. Decreased desire to train and decreased joy from training—that is if you even like training to begin with. Altered hormonal patterns including a reduction in anabolic, muscle building/fat burning hormones (testosterone, growth hormone, IGF-1) and an increase in catabolic, muscle destroying/fat storing hormones (cortisol).
This last one is the worst side effect for those concerned with body composition change. Physique development is way more complicated than just the simple calories in vs. calories out theory. It really comes down to properly managing and manipulating natural hormone levels and metabolic rate through diet and exercise. Do this the right way and getting into shape is a smooth process. Do it the wrong way, and dropping body fat will be impossible no matter how many calories you cut or how much you exercise.
Negative hormonal alterations (such as reduced testosterone/growth hormone and increased cortisol production) are the primary reason why many who overtrain struggle with fat around their midsection DESPITE their high levels of exercise. Abdominal-specific body fat often has a lot to do with abnormally high cortisol levels. These people tend to be fine everywhere else on their bodies, but tend to hold a lot of flab around the midsection.
I see this most often with endurance athletes. Research has shown that this group of athletes has the most compromised hormonal profiles—meaning lower than normal amounts of testosterone and higher than normal amounts of cortisol. People who engage in frequent and excessive amounts of aerobic activity are shooting themselves in the foot in terms of physique development. They may be improving performance (as in the ability to run farther or at a faster pace) but they are not optimizing hormones, metabolism, and thus, physique development results.
But it’s important to note that overtraining can happen in any form of exercise, including strength training. So don't think because you stay away from the treadmills and sling the weights around that you are immune to the overtraining syndrome. Every athlete needs to balance training with recovery.