Digital resistance vs weights: what really changes

"That can't be like iron." It's the most repeated line in our demos, usually from someone who's been training for years. And they're partly right: digital resistance isn't like iron. It's different in pure physics, and that difference has real consequences — most in its favour, some against. Let's explain them without the marketing.

What digital resistance is, exactly

In the Power S Pro, the load doesn't come from plates: it's generated by two 750 W servomotors that tension the cables with the force the screen tells them to — up to 120 kg total (60 per arm), adjustable in 0.5 kg steps and with each arm controlled independently.

That the load is software has a consequence iron can't imitate: it can change during the rep. That's where the 5 training modes come from — standard, elastic (more load the further you stretch, like a band), concentric (all the load on the pull), eccentric (more load on the way down) and burnout.

The physics: inertia, or why 60 digital kg feel harder

When you move a 60 kg barbell, you don't fight 60 constant kilos. Accelerating it at the start of the range gives it inertia, and that inertia "gifts" you part of the final stretch — anyone who's done a cheat curl knows exactly what we mean.

The motor gifts nothing. It holds the programmed tension across the whole range, at any speed: no initial jerk to ride the momentum, no rest at the top. Hence the category's unwritten rule: the same number in digital feels harder than in iron. If you come from benching 80 kg, don't start at 80.

Practical consequences:

More mechanical tension per kilo — and tension under control is the main driver of hypertrophy. You work as hard or harder with lower numbers.
Less peak joint stress: no jerks to overcome inertia, no rebound shocks. It's why this kind of load works so well in rehab and for the over-50s.
The eccentric phase finally works: with iron, lowering the weight is free unless you brake it yourself with discipline; the eccentric mode loads you more precisely there, where the stimulus is greatest (and where with iron you'd need a partner to lift the bar back up).

What iron still does better

Honesty required:

Absolute maximal loads. If you compete in powerlifting or your deadlift is clearly above the machine's 120 kg, iron is still your maximal-strength tool.
The barbell sporting movement. The Olympic snatch or clean, the back squat with the bar on your back: patterns a cable only partly replicates.
The ritual. The clang of the plates, the chalk, the room. It doesn't show up in any study and it decides more purchases than it seems. No irony: if that's what makes you train, it's worth gold.

For everything else — which is 95% of what most people do at the gym: presses, rows, pulldowns, cable squats, curls, raises — digital resistance isn't an acceptable substitute for iron; it's a version with more control.

The extra iron will never have: it watches you

The motors don't just generate load, they measure it. The machine records force and speed on every rep, and the Booster Mode acts as a spotter: when it detects fatigue getting the better of you, it reduces the load automatically so you finish the rep safely. Training alone at home, to failure, with no one to lift the bar off you: that problem is solved by design.

With iron, that same safety is called "a trusted partner" or "not really pushing." With software, it comes as standard.

The practical conclusion

Don't ask "do 120 digital kg equal 120 of iron?" — ask "what does my training need?" If it's progressive tension, joint control, a real eccentric phase and safety to train alone, digital resistance wins on home turf. If it's maximal strength with an Olympic barbell, keep the iron too; they're not mutually exclusive.

The theory you get by reading; the feel, you don't. Book a demo, ask for eccentric mode on your usual exercise and draw your conclusions with the cables in your hands.