Our philosophy page tells you what we believe: the minimum effective dose, applied with precision. This page shows you why it's true. Strength curves, moment arms, and the point where more training stops paying you back.
Concept one
Take a curl. With the arm extended you're weak. Around mid-range you're strongest. Near the top you weaken again. Plot the force a muscle can produce at each point of the range and you get a strength curve — and every muscle in every movement has its own shape.
Now consider what's resisting you. A dumbbell is pulled straight down by gravity with constant force. A machine with a round pulley delivers constant resistance too. Neither has any way to respond to your strength curve.
With constant resistance, the weakest point in the range decides the whole load. Pick anything heavier and you fail there. So the muscle is meaningfully challenged for a sliver of the movement and coasting through the rest — the shaded area is stimulus you paid for in fatigue and didn't collect.
A cam is a non-circular pulley. Because its radius changes as it rotates, the resistance it delivers changes through the range — and if the profile is engineered correctly, it changes to match the strength curve of the muscle it trains. Heavy where you're strong, lighter where you're weak.
That's the blue line. Same relative difficulty at every joint angle, so the set ends when the muscle is fatigued rather than when one position gave out.
Stated precisely, because the overclaim is common: you can reach muscular failure on a barbell. Of course you can. The question is where you fail.
With a mismatched resistance curve you fail at the sticking point while the rest of the range never saw a challenging load. You stopped because one joint angle gave out — not because the muscle was done.
Concept two
A moment arm is the perpendicular distance between the line of force and the joint it's rotating around. Multiply force by that distance and you get torque — the actual rotational demand on the muscle.
This is why a 20 lb dumbbell held close to your body feels light and the same 20 lb held at arm's length feels brutal. The weight didn't change. The moment arm did.
Every machine on a gym floor makes a decision about your moment arms — where the pivot sits, where the pads are, how the linkage is built. A well-designed machine puts the demand on the muscle. A poorly designed one puts it on the joint. That's the difference we're paying for on our floor.
Concept three
Adaptation doesn't scale forever with volume. It climbs steeply at first, flattens, and then declines — because past a point the extra work adds fatigue without adding stimulus.
The last 20% of the result costs roughly double the work — and that extra work is paid for out of your recovery, your joints and your week. Past the peak it isn't even a trade: you're adding fatigue and subtracting adaptation.
Concept four
This is the one that decides how a session gets written. Within a session, the useful stimulus from each additional set falls off quickly — the first hard set does most of the work. Fatigue behaves differently. It accumulates, and it accelerates.
Every set after the gap starts narrowing is buying less adaptation at a higher cost — and the cost is charged to the rest of your week. To your next session, your sleep, your joints, and to how well you recover on a deficit.
Now put the two ideas together.
Equipment that matches its resistance curve to your strength curve loads the muscle across the whole range — so each set delivers more stimulus for the same fatigue.
Which shifts the entire dose–response curve left. The minimum effective dose gets smaller. Better engineering doesn't just make training nicer. It means you need less of it.
Where this comes from
None of the above is a Hammer Fitness invention. It comes out of the biomechanics tradition that Tom Purvis has spent decades formalising through the Resistance Training Specialist programme — the most rigorous movement education available to a coach, and one that comparatively few trainers complete.
The core idea Purvis teaches is that an exercise is not a name, it's a set of mechanical conditions. A "chest press" isn't one thing. Change the pivot, the pad position, the grip or the path and you've changed which tissue is loaded, how much, and where in the range — regardless of what the exercise is called.
Amer Kamra, founder and head coach of Hammer Fitness, completed a Masters in Resistance Training under Purvis. It's why our machine selection reads as obsessive and our set counts read as low — those two facts are the same fact.
Choosing a machine whose resistance curve matches the muscle means a set produces more stimulus. Fewer sets are then needed for the same result.
Seat height, pad placement and joint alignment change moment arms — and therefore what the exercise actually trains. Same machine, different exercise.
We coach the muscular contraction, not the appearance of the lift. Making a light weight feel heavy is the objective; moving the heaviest weight is not.
In practice
This is what "less is more" means in mechanical terms, and it's why the equipment on our floor was assembled the way it was — one machine at a time, chosen for engineering rather than bought as a package.
Questions
The pattern of force a muscle can produce across a range of motion. In most movements you're weakest at one end, strongest somewhere in the middle, and weaker again at the other end. Each muscle in each movement has its own shape.
The resistance curve is how much the equipment pushes back at each point of the range. A free weight or a round pulley delivers roughly constant resistance, so the weakest point in your range dictates the load for the whole set. Match the resistance curve to the strength curve — which is what a properly profiled cam does — and the muscle is challenged throughout instead of at one angle.
The perpendicular distance between the line of force and the joint it rotates around. Torque equals force times moment arm, so lengthening the moment arm increases the demand on the muscle without changing the weight. It's why the same dumbbell feels light close to your body and brutal at arm's length.
The least amount of training that produces the adaptation you're after. It matters because the dose–response curve flattens: roughly the last fifth of the available result costs about double the work, and past the peak additional volume adds fatigue while subtracting adaptation.
Not less than the effective dose, no. The claim is narrower and more useful: past the productive range, extra volume costs recovery without buying adaptation. Better equipment and better set-up raise the stimulus per set, which lowers the number of sets needed — so you train less for the same or better result.
The founder of the Resistance Training Specialist programme and one of the most influential figures in applied resistance-training biomechanics. His central teaching is that an exercise is a set of mechanical conditions rather than a name — change the pivot, position or path and you've changed the exercise regardless of what it's called.
The principles apply to any tool — set-up, position and moment arms can be managed with free weights and cables too. Well-engineered machines just make it far easier to load a muscle correctly through a full range, which is why we invested in them rather than filling a floor with whatever was cheapest.
Free — no commitment
Book a consultation and we'll show you the difference on the floor — the same movement, set up two ways, so you can feel what a matched resistance curve actually does.
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