What happens when you miss a workout?

Question

Normally I get to the gym Mondays, Wednesdays and Fridays and try to lift a little bit more weight than I did the time before.

Today everything has gone wrong and I am not going to be able to make it to the gym.

Biologically speaking what is happening to me now?

Are my muscles shrinking rapidly and my skeleton imploding completely trashing any hopes I have of lifting again? Or is it fairly harmless and my muscles will stay the same and may even benefit from the extra rest?

How many times would I have to miss working out before it starting to seriously set my progress back?

Answer 1

NASA has done muscle atrophy testing by requiring bed rest in a water-bed like matress for up to six weeks to see the affects of low gravity and inactivity. A study followed up on the NASA (Neural factors account for strength decrements observed after short-term muscle unloading) tests by testing muscle fibers and blood work after 2 weeks of inactivity. The result was "The 14-day intervention failed to alter the size or fiber type distribution of muscle samples. However, resting plasma cortisol levels were significantly increased after muscle unloading, suggesting an endocrine environment favorable to muscle atrophy." There was some reduced muscle function, which they chalked up to neural degeneration, since muscle remained.

In other words, after two weeks of complete inactivity, you do not lose muscle, but your blood has markers that suggest muscle atrophy is on its way. However, there is neural degradation, so some strength is lost. After one day, or just a few, it appears more likely that recovery is happening without any loss.

Answer 2

I would say that you start to lose strength gains from missing a couple of weeks. This is from personal experience.

Having about 5 days off occasionally is good for me at least. It's good to give your body a complete rest occasionally. I often find that rest can benefit big compound exercises like squats and deadlifts.

Answer 3

The fact is that nothing remains constant in the body. After any training period your muscles will go through a recovery phase, followed by a supercompensation phase. If you train or seriously exert yourself again towards the end of the supercompensation phase, those phases will repeat. If you do nothing, muscle atrophy will begin. The rate will be slow even if completely bedridden, but it will occur nonetheless.

The big question then is how long is the supercompensation phase. And like all big questions, the answer is complicated. It depends on what type and intensity of training you've been going through, how long the macro cycle of training has been occuring, and how close to your body's potential you are currently performing at.

For practical purposes, most people can easily take a week off without suffering significant setbacks.