Where 3x10 and 5x5 came from: a short history of gym numbers

Almost every training plan ever handed to a beginner says 3x10 somewhere on it. Almost every strength programme says 5x5. Those two numbers have been circulating in gyms for about seventy years, and hardly anyone can say where they came from.

Before the numbers, there was only "add a bit more"

The oldest strength training story is the one about Milo of Croton carrying a calf every day until the calf became a bull. It is a legend, not a record, but it captures the only principle the ancients had: the load has to go up. Greek athletes did use halteres, stone or metal weights with a handle, yet nothing tells us how many sets they did.

The reason is simple. Until the late 19th century there was no standard barbell with removable plates, so there was nothing precise to count. The strongmen of that era performed in front of an audience and lifted once, for effect, not ten times in a row.

3x10 was invented in a hospital

Three sets of ten did not come out of bodybuilding. It traces back to military rehabilitation after the Second World War and to the physician Thomas DeLorme, who was looking for a faster way to rebuild leg strength in wounded soldiers.

The original protocol went like this: find the heaviest weight a person can lift exactly 10 times, then perform three sets of 10 — the first with half that weight, the second with three quarters, the third with the full amount. The first two sets are effectively a warm-up built into the plan.

It caught on because it was safe and measurable. Nobody had to test a true one-rep maximum to set the load, which mattered enormously in a hospital ward, and it is still the sensible route today — there is a whole method for estimating your 1RM from working sets instead of grinding out a max. When the scheme escaped into commercial gyms, only the skeleton survived: three sets, ten reps, same weight throughout.

5x5 came from heavy lifting

Five sets of five belongs to a different family. In the 1950s it is associated with the British physique competitor Reg Park, who built both size and strength on relatively few reps with heavy weights. In the 1970s the American strength coach Bill Starr pushed it into team sports, where the job was writing one workable plan for fifty athletes at once.

Five reps is a compromise. It is heavy enough to genuinely build strength, and short enough that technique does not fall apart in the last rep of a set. That is why 5x5 is nearly always written for the big barbell lifts — squat, press, deadlift, row — and why it pays to settle which squat variation you are running before you start piling on weight.

Why ten and five, rather than nine and six

The first reason is dull: we have ten fingers and we count in tens. Round numbers are easier to remember, easier to write down and easier to track. The same habit that produced the names of our muscles and lifts produced round set counts — whatever is easy to say is what sticks.

The second reason is equipment. An Olympic bar is 20 kg, the smallest commonly available plates are 1.25 kg, so the smallest symmetrical jump is 2.5 kg and the next practical one is 5 kg. When everything in the room is measured in fives, programmes get written in fives too.

The third reason is workload. 3x10 gives you 30 reps, 5x5 gives you 25 — close on reps, nowhere near on load. Squatting 3x10 with 60 kg is 1,800 kg of total work; 5x5 with 85 kg is 2,125 kg, and every single rep is far harder. One scheme leaves you pumped, the other teaches your body to be strong.

What we actually know about these numbers

The short answer: neither is magic. Research mostly points to the same three things for muscle growth — the total number of hard sets per muscle group across the week, how close to failure you train, and whether the weight climbs over months. A wide rep range, roughly 5 to 30, produces similar growth as long as the sets are genuinely difficult.

For maximum strength the evidence is strongest for heavier loads and lower reps, because lifting heavy is a skill as much as a muscle property. That is the one place 5x5 has a clear edge.

What is not settled: the exact weekly set count beyond which extra work stops paying, how much that varies between people, and where the ceiling on muscle growth actually sits. Anyone claiming one precise number for everyone is claiming too much.

Putting it to work

If you are new, 5x5 on two or three big lifts plus 3x10 on the accessories covers almost everything you need. Three sessions a week is enough.

Progress in small steps: 2.5 kg on upper body lifts, 5 kg on squats and deadlifts, and only after every set was clean. When you stall two weeks running, drop the weight by roughly 10% and climb back up. That is not failure, it is how the cycle is supposed to work.

And the scheme is a frame, not a law. 4x8 is not worse than 3x10 just because it is less round.

When to see a doctor

Get checked if you have sharp pain at one specific point in a movement, pain that lingers for more than a few weeks, numbness or pins and needles down an arm or leg, a swollen joint, or chest pain, dizziness or breathlessness on exertion. The same applies if you have high blood pressure or heart disease, or you are coming back from surgery — that conversation comes before the choice of scheme.

The short version

• 3x10 comes from post-war military rehabilitation, where the three sets were steps: half the load, three quarters, then full.
• 5x5 comes from heavy lifting in the 1950s and 1970s, where five reps balanced a heavy bar against clean technique.
• The numbers are round because we count in tens and because the kit gives us 2.5 kg and 5 kg jumps off a 20 kg bar.
• For growth, a wide rep range works similarly; hard set volume, proximity to failure and progression over months decide the outcome.
• For strength, the evidence favours heavier loads and lower reps, which is where 5x5 beats 3x10.