There are some very smart, knowledgable people in the fitness industry that will tell you that you should only work out for forty five minutes to an hour or you’ll go catabolic. Meaning your body will start to attack lean muscle tissue for energy. The reasoning behind this is due to the fact that cortisol – your body’s stress hormone – spikes around this time period.
Let’s think about this logically. The hormones in your body do crazy things all day long. Sure, working out for prolonged periods of time will spike your cortisol levels. So will stressing over a big assignment at work. Or pounding that energy drink you need to make it through your day. Cortisol, growth hormone, insulin, testosterone; all these hormones will vary quite a bit over the course of an average day. So what does this mean for muscle growth/fat loss?
Because of what people have heard or think they know about steroid use, there seems to be an over-emphasis on hormone levels as they relate to fitness. What people don’t understand is that professional bodybuilders are ingesting massive amounts of these hormones in order to get the desired effects. Your natural hormone levels varying over the course of one day is not going to be even remotely comparable to taking something synthetic. So no, a spike in cortisol levels – or any natural hormone, for that matter – is not going to have an acute effect.
That said, training for hours at a time can be detrimental to progress. The reason for this, though, is the amount of calorie expenditure it takes to sustain a training program like this. If you’re trying to put on weight, it will be extremely difficult to keep up with your food intake. If you’re trying to lose weight, you may slow your metabolism and lose muscle by putting yourself in too severe of a deficit. You need to find a training length that gives you the results you want without reaching a point of diminishing returns.
Again, the key here is going to be your nutrition. At the end of the day, have you eaten all your calories, proteins, fats, carbohydrates? If so, you’re going to make progress, period. When I first started training I would train for a minimum of two hours a day. Was this necessary to see results at this stage? Definitely not. It was overkill. But my nutrition was on point so I continued to grow.
Again, and I can’t stress this enough, people need to stop thinking about muscle growth in terms of a single day. Your body doesn’t work that fast. What you’re trying to do takes time and consistency. You need to stick to a good nutrition plan for weeks to see any noticeable difference in your body. Do that, and a little bit of cortisol is not going to hurt you.