Matching Resistance Profiles to Human Strength Curves: Ascending vs Descending

Ever noticed that a squat feels impossible in the hole and almost easy near lockout? That gap is the idea behind resistance profiles and strength curves. Your strength changes with joint angle, but a barbell weighs the same all the way up, so some parts of the rep end up hard and others end up soft.

This article is a cluster of our exercise selection and biomechanics guide. Here we cover the three common curve shapes, how mismatch shows up, and what cables, bands, cams and body position can do about it. Where the evidence is thin, I will say so.

What are resistance profiles and strength curves?

Two terms, easy to mix up.

• Strength curve: how much force you can produce at each joint angle. It comes from muscle length (force changes as a muscle stretches or shortens) and from lever arms (joint angles change the moment arm). Our moment arms and joint torque article covers that side.
• Resistance profile: how much torque the exercise demands at each angle. Free weights have a constant load but a changing demand. Cables, bands and cams change the demand in other ways.

A good match means the exercise challenges the muscle across the range you care about. A poor match means one short stretch of the rep is the hard part and the rest is a free ride.

One caution up front. The shapes below are simplified. Real curves vary by joint, by person, by limb length and by how you set up. Treat them as a starting point to test, not a law.

Ascending vs descending vs bell-shaped curves

Ascending. You are weakest at the start and strongest near lockout. Squats, leg press and pressing movements are the classic examples. The bottom of a squat is where the lever arms work against the hips and knees, so that is where most failed reps stall, usually a little above the very bottom.

There is some measured support here, with a caveat. In 18 men doing maximal isometric leg presses, knee torque showed an ascending-descending pattern across knee angles from 30 to 100 degrees of flexion, with an optimum shifted toward extension compared with single-joint literature (Hahn et al., 2011). That was isometric, in one machine, and in men only, so it does not describe your squat exactly. It does show that leg strength is not flat across angles, and that single-joint and multi-joint tasks behave differently.

Descending. You can produce the most force when the muscle is long and less as it shortens. Pulldowns and rows are often described this way, but it depends on the joint and the person, so I would hold that label loosely.

Bell-shaped. Force peaks in the middle and drops at both ends. Elbow flexion (curls) is the usual example, with strength highest somewhere in the middle of the range.

Why a mismatch makes sets less efficient

Take a standing barbell curl. Gravity pulls straight down, so the torque on your elbow is biggest when the forearm is horizontal and falls toward zero at the bottom and the top.

Your strength is also bell-shaped, but the two shapes do not overlap perfectly. The practical result is that the set is limited by one portion of the range and the rest is lightly loaded. You do not “waste energy” in any dramatic way. You just get less useful tension in the easy zones.

The most common mistake here is blaming yourself when the real issue is the setup. A curl that feels dead at the top is not a lack of effort, it is the load direction.

Do variable resistance tools work better?

Variable resistance means changing the load through the rep, usually with bands, chains or cam machines. The evidence is genuinely mixed.

• A 2022 meta-analysis of 17 studies and 491 healthy adults (aged 18-37) found no significant difference in maximal strength or muscle power, upper or lower body, between variable and traditional training. For lower-body strength, traditional training did better when sets had more reps (Andersen et al., 2022).
• A 2022 meta-analysis of 14 studies found variable resistance gave greater maximal-strength gains overall (ES = 0.80). In trained people the benefit appeared at loads of 80% of 1RM or more, while untrained people benefited at loads below 80% (Lin et al., 2022).

Why might they disagree? Different study pools, different definitions of variable resistance, small trials and different outcome tests. A cautious reading: variable resistance can help some people at some loads, but it is not a clear upgrade. It is a tool, not a requirement.

Bands specifically look similar to weights for strength. A meta-analysis of eight studies found no difference between elastic and conventional resistance for upper or lower limb strength (Lopes et al., 2019). Note these were strength outcomes, so this says little about muscle size.

How to match the profile: cables, bands, cams and body position

Free weights: change the angle, not the weight. The load is constant but the torque is not. Tilting the bench, leaning the torso or changing your grip moves the hard point. Our free weights vs cables vs machines article compares these options in more detail.

Cables: keep tension where gravity quits. A cable keeps pulling when a dumbbell would no longer resist, such as the bottom of a lateral raise or the top of a curl, depending on pulley height. Pulley height and line of pull decide where it feels hardest, which is the whole topic of cable setup and pulley angles. For fibre-direction logic, see line of pull and muscle fibre alignment.

Bands and chains: add load near lockout. As a band stretches or a chain leaves the floor, resistance rises, which suits ascending lifts like squat and press. A heavy band at home is a budget-friendly way to do this.

Machine cams: shape built in. Cam-based machines try to shape resistance for you. Fit depends on the design and on your body, so we cover how to test it in selectorized machine cam profiles. I do not go deep here to avoid overlap.

Where in the range should the hard part be?

Here the strength curve and muscle growth research meet, and the findings are interesting but not final.

A systematic review of six studies found full range of motion beneficial for lower-body hypertrophy compared with partial range, while upper-limb evidence was limited and conflicting (Schoenfeld and Grgic, 2020).

A more recent trial in 30 resistance-trained people trained each arm with either lengthened partial reps or full range for 8 weeks. Muscle thickness and lat pulldown strength-endurance improved similarly, and the authors concluded that emphasizing the stretched position is likely wise for muscle size (Wolf et al., 2025). That is upper body only, and eight weeks is short.

The best-known example with cables: in a 12-week trial of 21 adults, cable elbow extensions in the overhead position (long head of the triceps stretched) produced about 1.4-fold greater whole triceps growth than the neutral position (+19.9% vs +13.9%), even though lighter loads were used (Maeo et al., 2023). It is one muscle in one study, but it fits the idea that the stretched part of the range matters.

Applying this to common lifts

Squat and leg press (ascending). The bottom is the hard part. Use full range if your mobility allows, control the descent, and consider bands or a pause.

Leg curl. Seat position changes hip angle and the stretch on the hamstrings, so test it rather than assume.

Curls (bell-shaped). Try preacher or cable curls if the top of your barbell curl goes slack. Incline dumbbell curls bias the stretched position.

Rows and pulldowns. The stretched position is at the start. Let the shoulder blade move, keep control at the bottom, and add a short squeeze at the top.

You can fold these ideas into a program using our free leg day plan, or browse the push, pull and legs plans.

Common mistakes with strength curves

1. Chasing a perfect match. No equipment matches every person. Aim for “good enough” and use the rest of the program for coverage.
2. Ignoring the dead zone. If the top of every curl and lateral raise is slack, that muscle gets less useful tension per rep.
3. Shortening the range to lift heavier. Ego partials in the strong zone can reduce stretch, which the research above suggests matters for lower body growth.
4. Buying gear before testing a setup change. Pulley height, bench angle and seat position are free.
5. Over-reading studies. Many trials are short, use young adults, and measure strength, not muscle size.

The bottom line

Resistance profiles and strength curves are a useful lens, not a magic formula. Strength changes with angle, torque demands change with lever arms, and equipment can reshape the mix. Evidence for bands, chains and cams beating plain training is mixed. Evidence for full range of motion in the lower body, and for training the stretched position in muscles like the triceps, looks more promising, but it comes from small, short studies.

Test where each exercise feels hard, adjust the angle or cable until your target muscle is loaded through the range, and keep progressing. If you have pain at a specific joint angle, that is a reason to see a physiotherapist or doctor, not to push through it.