I was recently asked "is it harder to build muscle when you're older". The answer: Yes. Impossible? Of course not. As people age there are lots of things that happen in the body that makes everything a little bit harder and here is the breakdown. Unfortunately, as you age your muscles start to atrophy (shrink) and lose the ability to hypertrophy (get bigger) and the cause of this is not too well understood as far as researchers are concerned. What they do know, is that around 50 your strength begins to decrease by a certain percentage each year and this is inevitable, even if you've been lifting weights most of your life. The main reason muscles begin to atrophy is protein degradation; the proteins in your body are just not rebuilding and repairing muscle tissue as fast as they once were. As people age, they also have a harder time fighting the common cold or may come down with more serious ailments that cause them to be bed ridden for any amount of time and that will also greatly affect the ability to build muscle. Now for those of you who aren't yet out of your prime, it's never too late to start so don't feel like it will all be for wasted effort. Will you look like a VS model? No, because not only are they on crazy diets and air brushed, they are younger and looking like that is their career. Will you have more energy and feel better? Absolutely.
Now, everyone knows muscle burns more fat at rest, so even if you can't see the muscles you have, they are there, and they are doing something and you should work to build them, but at a safe and moderate pace. Also, never take cardio for granted! The heart is a muscle and working that even just a little can do wonders for anyone's health, young or old.
1. Nerves slow down.Your nerve endings and fibers start to fire more slowly as you begin to age. This means it might take you a second longer to think about how to do something because the neural pathway is no longer active. Muscle does have memory, but it's not immediate! A bicep curl or squat might not be second nature, even after a few weeks of exercising you might not have perfect form but exercising works those nerves and the brain, as well as the muscles.
2. Collagen levels decrease. Collagen is what keeps things looking smooth and tight. This is why anti-wrinkle creams have collagen in them. Collagen is found in the skin, and once lost there is only so much you can do to restore it. Start taking care of your skin NOW... avoid sunburns, use moisturizer, keep your muscles toned. Excess fat stretches the skin, and as you age your skin has less elasticity to bounce back after weight loss.
3. Muscle proteins decrease. The body just doesn't put as much work into building the muscle as much as simply repairing it. Still, repairing the small tears you create from strength training will help to hypertrophy the muscles a bit.
The bottom line is, building muscles takes a large commitment and aging is inevitable. But if you have realistic goals, there is no reason to not start, just know it might take a little more "sweat, blood and tears" motivation to get the results you want. Every body has a genetic "set point"; a weight and size it prefers to be. Of course the set point can be modified through diet and exercise, but usually where you hit your plateau is a good indicator.
My biggest suggestion; learn to love your body for what it can do, has done, and will do rather than hate it for what it cannot. Being healthy is always the ultimate goal, and health comes in all shapes and sizes.