So I found a fascinating article the other day, only I can’t remember where I found it and why I downloaded it. It’s by Michael Rennie and it’s called “Body maintenance and repair: how food and exercise keep the musculoskeletal system in good shape.” Ooh, here’s a link. I figured it would be dense in biochemical lingo and biostatistical mumbo-jumbo, and of course, it is. But it’s an amazing review of everything we know (or what we knew in 2005) about the downstream signalling of diet and exercise and it’s effect on muscle mass. Here’s a summary:
Point One: Muscle Is A Dynamic System
Muscle is constantly building up and breaking down. All day, every day. The paper likens it to a bank account with frequent withdrawals and deposits, which is true. It’s also similar to bone metabolism, an interplay between building and breaking/down repairing that ultimately creates fresher, stronger, more structurally sound bone, as long as you give it the right stimuli. And it turns out that those two mechanisms are somewhat independent of each other, so to build muscle optimally while keeping breakdown to a minimum, you should do the following things:
Point Two: Protein is King
Only one thing stimulates actual muscle growth: protein. Protein that you eat gets broken down into amino acids, and when blood amino acid levels hit a certain concentration, it turns out signaling that makes muscle take up those circulating amino acids and add it to the existing structure. More specifically, one amino acid (leucine) stimulates the pathway. It takes a certain threshold level (you can’t build muscle eating 5g of protein every hour, compared to 40g 3 times a day), but once you hit that level, there’s a linear relationship between protein intake and muscle growth. The plateau occurs way beyond normal human intake levels.
It doesn’t seem to matter how often you eat your protein and how much you eat at one time… with a catch. The catch is that protein synthesis occurs in 30 minute blocks, and then it just shuts off. The paper doesn’t say for how long. So if you can down 100g in 10 minutes, more power to you. But if it’s taking you an hour to eat a 3-lb steak, some of it might be going to waste.
Point Three: Keep Your Muscle by Eating
Just like there is one major stimulus to building muscle, there is only one major stimulus to preventing muscle breakdown: insulin. The more frequently you have insulin on board, the less muscle you break down. Not to say that you should stuff yourself with sugary snacks all the time, because that makes your muscles *resistant* to muscle-building effects of protein. All it takes is a normal basal level to prevent breakdown. That is, don’t fast for too long. If you fast frequently enough and don’t do anything to stimulate *building* muscle, you’ll lose it all. Occasional fasting mixed with stimuli that build muscle might be helpful. Just ask Martin Berkhan.
Point Four: Lifting Makes It Better
What happens when you work out (and by work out, I mean “lift heavy”)? You start to break down muscle, for one. Exercise causes muscle tears and damage that need to be fixed. However, the same exercise can turn on those muscle building pathways and supercharge them. If you eat 50g protein after a lift, it’ll do a hell of a lot more for your muscle than if you just eat it at rest. But at the same time, you need to stop the muscle catabolism that comes from exercise. And the ideal way to do this is a maximally insulin-stimulating meal (ideally protein and carbs, little-to-no-fat) right after working out.
The paper also suggested that working out with *any* weight higher than 65% of your 1-rep max will stimulate muscle growth equally. Sets of five, a la the Mark Rippetoe program, work in the 80-85% range, but the paper suggests you could build size (size, mind you, not necessarily strength) with sets of 12-15 to failure. Exercise with lighter weights and/or jogging/walking does none of this. Surprise, surprise.
What should you do, based on this information? Pretty much what you expect. Eat about 1g protein per pound of lean body mass. Lift heavy things, more often if you want to get strong, less often if you want to maintain or build a bit of muscle. Don’t spike insulin levels, unless you’ve just finished a workout, in which case, by gawd, spike the hell out of it (with glucose and starch; muscle doesn’t take up fructose to replenish glycogen, it goes to the liver instead.) You *could* just have protein after a lift, or fast for a couple hours. This may stimulate some extra fat loss, but you’re sacrificing a bit of muscle mass and a lot of performance. Worked great for Richard Nikoley of Free the Animal when he was focused on fat loss. Also works for Mark Sisson, since he’s not as keen on getting progressively stronger as he is on staying lean. So that’s that.
Next time: my awesome new sleep app.