When you do strength training while not eating enough calories or protein, your body might build muscle in the areas you're working while actually shrinking muscle in the areas you're not. It's like your body is shifting resources from one place to another to cope with the stress and low fuel.

If you do targeted strength training for a few weeks, the muscles you work will grow bigger, but the muscles you don't use during those exercises might actually shrink a little bit. This happens because your body adapts specifically to the exact movements you're doing.

Even lifting light weights, as long as you push until you can't do another rep, can build muscle just as well as lifting heavy weights in people who already train regularly.

You can't really grow bigger muscles until you've done about 18 weightlifting sessions—your body needs time to adapt before it starts building real muscle.

You can build muscle by working one arm or leg at a time, even if your body doesn’t show higher levels of muscle-building hormones in your blood—so maybe it’s the physical stress on the muscle itself, not the hormones, that makes it grow.

People grow muscle at very different rates — but each person tends to grow their arms and legs similarly, no matter what weight they use. This means your genes and biology matter more than how heavy your weights are.