How muscles get stronger

A muscle doesn't grow because you're sore, sweaty or tired. It grows because it was asked to produce real tension, often enough, and then fed and rested.

Tension is the signal

Same Ian, same squat, three loads. Only one of them tells the muscle it needs to get stronger.

The last reps are the ones that count

A muscle is a team of fibres. On easy reps only a few show up. As it gets hard, the big strong ones get called in, and those are the ones that grow.

The stretch alarm

Every muscle has sensors inside it called muscle spindles. They watch how far the muscle is stretched, and how fast. Stretch it fast and the muscle tightens by itself, before you can think.

White zigzag: the stretch sensorWhite dots: "I'm being stretched"Green dots: "Tighten up"

This is why easing into a stretch works better than forcing it, and part of why a quick bounce is stronger than a jump from a dead stop.

What grows a muscle, and what doesn't

The list on the left is boring on purpose.

DoesSets where the last couple of reps are slow and hard. Enough of those each week. A little more over time: a rep, a few pounds. Protein. Sleep. Months of it.
Ian: "Nobody wants to hear 'months'. It's months."

Doesn'tBeing sore. Sweating a lot. The burn. "Confusing" the muscle. A new program every week. Feeling destroyed.
Ian: "Sore means you did something new. It doesn't mean you did something useful."

The kid version

For explaining it at the kitchen table.

Your muscle is a team of tiny helpers. For an easy job, only a few helpers show up. For a hard job, everybody has to come. When everybody had to work hard, your body says, "We need a bigger team," and builds more while you sleep. So the hard reps are how you tell your body to hire help. And your muscles also have a safety alarm: stretch one too fast and it tightens up on its own to protect you.

This week

Pick one.

Find "hard enough"On one exercise, pick a weight where reps eight to ten are slow. If ten felt like one, it was too light.

Write it downWeight and reps. Next week, beat it by one rep or a few pounds. That's the whole system.

Ease into stretchesSlow in, breathe, hold. If you bounce into it, the alarm goes off and the muscle fights you.