check your daily calorie intake shop my training programs What happens to your body when you stop lifting weights? This is a common question a lot of folks are asking right now as the global pandemic has most people training in some limited capacity Key Points: Research shows that we tend to lose muscle very quickly with complete bed rest – mostly due to suppressed muscle protein synthesis. Doing any kind of physical activity will maintain muscle much better than doing nothing. You can prevent muscle loss through training (even minimal bodyweight workouts) and diet (eating at maintenance calories and consuming sufficient protein). Even if you lose size, muscle memory will rebuild lost mass quickly. Key Terms: Detraining: When you stop training and lose gains Training Volume: How much total work you’re doing in the gym. Usually approximated as the number of tough sets. I want to start with a real-life example of muscle loss. Matt H is a pro natural bodybuilder and client of world-renowned physique coach, Cliff Wilson. After being hospitalized with Crohn’s flare-up, Matt was forced to take a significant break from training. He went from 200 lbs on the left, all the way down to 166 lbs on the right, at about the same body fat. This means he lost just about 35 pounds of pure muscle! Breaking Down the Cause of Muscle Loss Before we dig into those questions, it’s important to first understand that muscle loss is a complex process – an ongoing tug of war between muscle protein synthesis and muscle protein breakdown, where gradually, the muscle protein breakdown side starts to win. [Hey, quick interruption here. One thing I’m struggling with this blog is knowing how much detail to include compared to my YouTube videos. I know that I definitely want more detail — but how much is too much, you know? I guess I’ll just have to wait to get some feedback from you all on that. Anyway, if you’re in the mood for some mechanism and theory, just keep reading. If you’re only here for the applied info, scroll down to “How Long Does It Take To Lose Muscle?”] We can think of skeletal muscle as a big brick wall: muscle protein synthesis is the process of adding bricks to the wall, while muscle protein breakdown is the process of removing them. These two processes are always occurring, and regularly swap turns taking the lead as we alternate between a fed and a fasted state. When we’re in a fed state, we tend to be adding bricks to the wall (assuming we ate enough protein in that meal) and we tend to be removing bricks from the wall when we’re in a fasted state (~8 hours after the last meal was consumed).1 What really matters for muscle gain and muscle loss in the long term balance between these two opposing processes. This balance, which we’ll call net protein balance, determines whether we gain, lose, or maintain muscle mass. If muscle protein synthesis is greater than muscle protein breakdown for a sustained period of time, more bricks are added than removed, and the wall gets bigger. We call this, positive net protein balance. On the other hand, if muscle protein synthesis is less than muscle protein breakdown for a sustained period of time, more bricks are removed than added, and consequently, the wall gets smaller. We call this negative net protein balance. While we know that muscle protein breakdown must exceed muscle protein synthesis for us to lose muscle, there are actually several different ways this can occur: 1) muscle protein synthesis can decrease, 2) muscle protein breakdown can increase, or 3) some combination of these two processes can occur simultaneously. Because feeding itself impacts protein metabolism, in order to figure out which of these three scenarios occurs when we stop lifting, we need to consider the impact of detraining on protein metabolism in both the fed state and the fasted state.  Let’s start with the fasted state. Gibson et al. (1987) was the first study to examine the effects of muscle disuse on muscle protein balance in the fasted state in humans.2 They had six men place one of their legs in a long-leg plaster cast and after five weeks, measured muscle protein synthesis and breakdown following a 12 hour overnight fast. They found that muscle protein synthesis had decreased by ~26% when compared to the non-immobilized leg, while muscle protein breakdown had remained unchanged. [Hey, another quick interruption. I hope you’re enjoying the blog so far. I’m enjoying writing it! I just wanted to say that I’m happy you decided to go the “mechanism and theory” route and didn’t just jump to the applied stuff. If you’re actually reading this, I’d love it if you sent me a DM on Instagram saying “purple monkey dishwasher” so I know people are actually reading this part. Thanks!] Since then, these same basic findings have been replicated many times in studies of prolonged muscle disuse (>10 days).3-6 What these studies find is that muscle protein breakdown will sometimes increase in the first two weeks, but then quickly return to baseline (i.e. to pre-disuse levels). Muscle protein synthesis, on the other hand, decreases in the early stages of disuse (somewhere in the first ~10 days) and then remains depressed.3 This implies that when we stop lifting, the majority of muscle loss in the fasted state is coming from “less bricks being added to the wall” rather than “more bricks being removed from the wall.” Of course, detraining could impact the wall differently, once we eat food. So let’s take a quick look at what the science says about muscle disuse in the fed state. Glover et al. (2008) was the first study to examine the effects of muscle disuse on muscle protein balance in a fed state.6 They had twelve young, healthy participants wear a knee brace for 14 days in order to immobilize one of their legs. After this period of time, they infused amino acids using IV at both high and low doses and measured the muscle protein synthetic response in both the immobilized