Machine Preacher Curl: How to Do It, Muscles Worked, and Setup

The machine preacher curl is a seated bicep isolation exercise. An angled pad pins your upper arm in front of your body and a lever arm fixes the path of the curl, so the only job left is flexing the elbow. In our military fitness programs, it is accessory work, not a main lift. It builds elbow-flexor strength that supports pulling, carrying, and holding onto loads for long periods.

That locked path makes this the most controllable curl in the gym, which is why it is worth doing correctly. This guide covers the muscles it works and which biceps head it favors, how to set up and run each rep, how the machine compares with dumbbell and barbell versions, the mistakes we see most, and how to program it.

What Muscles Does the Machine Preacher Curl Work?

The machine preacher curl works the biceps brachii, brachialis, and brachioradialis, while the forearm flexors hold the handles isometrically. The pad holds the upper arm still, which removes shoulder swing and torso momentum, so the elbow flexors move the load on their own.

Each muscle has a specific job in the movement:

• Biceps brachii: flexes the elbow and supinates the forearm (turns the palm up), so an underhand grip loads it fully.

• Brachialis: a pure elbow flexor under the biceps that works at every grip angle. It contributes much of the thickness of the upper arm.

• Brachioradialis: the forearm muscle that takes on more work when the grip is neutral (palms facing each other).

• Forearm flexors: grip the handles throughout the set without changing length.

This is why the preacher curl carries over to tactical work. Rope climbs, casualty drags, and long carries all depend on elbow flexors and grip holding up under fatigue.

Which head of the biceps does the machine preacher curl work?

Both heads of the biceps work on every rep. The preacher position flexes the shoulder, which shortens the long head (it crosses the shoulder joint) and leaves the short head in a stronger working position. The result is a modest short-head bias, not isolation.

Modest is the accurate word. You cannot switch one head off. EMG research on curl variations shows that shoulder position changes where in the range the biceps fires hardest, more than it changes which head does the work (Oliveira et al., 2009; Marcolin et al., 2018). If you want more long-head emphasis, pair the preacher curl with a curl done with the arm behind the body, like an incline dumbbell curl.

How to Do a Machine Preacher Curl

To do a machine preacher curl, set the seat so your armpits sit snug against the top of the pad, line your elbows up with the machine’s pivot, and curl the handles without lifting your upper arms. Lower under control for two to three seconds and stop just short of locking out.

How to set up the preacher curl machine

1. Adjust the seat height until your armpits rest against the top edge of the pad and your upper arms lie flat along it. Too low and your shoulders shrug up. Too high and you fold over the pad.

2. Line your elbows up with the pivot point, usually marked by a dot or axis cap on the lever arm. If the elbow sits in front of or behind the pivot, the resistance curve is off and the handles drift on the way up.

3. Take an underhand grip about shoulder width apart. Use the neutral handles if the machine has them and you want more brachioradialis work.

4. Select a load you can lower slowly on every rep of the set.

How to perform each rep

1. Start with your arms nearly straight, keeping a slight bend so the biceps stay under tension.

2. Curl by bending the elbow only. Your upper arms stay glued to the pad.

3. Squeeze at the top and pause for a beat.

4. Lower for two to three seconds. The eccentric phase is where much of the training effect lives (Roig et al., 2009).

5. Reach the bottom under control and start the next rep without bouncing.

The seated preacher curl machine has one big advantage over free weights here: setup does the stabilizing for you, so all of your attention goes to the curl itself.

Machine preacher curl form cues

• Armpits on the pad.

• Elbows on the pivot.

• Wrists straight, not curled in.

• Lower it slower than you lift it.

Machine vs. Dumbbell vs. Barbell Preacher Curl

The machine preacher curl is best for strict, repeatable isolation. The dumbbell version is best for correcting side-to-side imbalances, and the barbell or EZ bar version lets you load the heaviest. None is objectively better. Each solves a different problem, so choose by what you need from the set.

• Machine: fixed path, resistance shaped by a cam, fast load changes, and minimal setup skill. The trade-off is that a fixed path may not fit every arm length, and many models move both handles together.

• Dumbbell: unilateral, so the weaker arm cannot hide, and the wrist rotates freely. Tension fades near the top as the forearm approaches vertical. The dumbbell preacher curl is the free-weight counterpart to this movement and the natural next variation to learn.

• Barbell or EZ bar: bilateral and the heaviest of the three. The angled EZ bar grip is more comfortable on the wrists for many lifters than a straight bar.

Machine versus free weight is less important than most lifters think. A 2023 review found free-weight and machine training produced similar muscle growth (Haugen et al., 2023). Pick the tool you can train hard and consistently with.

Bicep curl machine vs. preacher curl machine

Many gyms label the same selectorized arm curl machine both ways. The defining feature of a preacher curl machine is the angled pad that holds the shoulder flexed in front of the body. Other “bicep curl machines” set the arm more upright or use a cable, which changes where in the range the movement is hardest.

Is the Machine Preacher Curl Good? The Constant-Tension Advantage

The machine preacher curl is a good bicep exercise because its cam or lever design spreads resistance across the full range instead of loading only the middle. That keeps the biceps working at the bottom, where the muscle is long, and near the top, where free weights unload.

The physics explain why. With a dumbbell on a preacher pad, gravity pulls straight down, so the load is hardest when your forearm is horizontal and drops toward zero as your forearm approaches vertical. A machine uses a cam or lever to change the effective resistance through the range, so the top of the curl still demands work (Schoenfeld, 2021).

The bottom of the range matters most. Training the elbow flexors through a full range of motion on a preacher curl produced greater strength and muscle thickness than partial-range training (Pinto et al., 2012), and preacher curl training focused on the lengthened, lower part of the range outperformed training at the top (Pedrosa et al., 2023). Broader reviews point the same direction (Schoenfeld and Grgic, 2020; Pallarés et al., 2021).

For a tactical athlete, the other benefit is cost. The movement carries almost no spinal load, takes little skill, and causes little fatigue, so it fits after heavy work without stealing recovery from the lifts that matter more.

Preacher curl machine average weight

There is no meaningful average weight. Manufacturers use different cam profiles and lever ratios, so 60 pounds on one stack can feel like 40 on another. Track your own numbers on the same machine and progress them over time.

Common Machine Preacher Curl Mistakes

Most machine preacher curl mistakes come from going too heavy, which shortens the range, adds momentum, and shifts work away from the biceps. Each one has a simple fix.

• Cutting the bottom off the rep. You skip the lengthened position that drives the most growth. Fix: lighten the load and reach near-full extension on every rep.

• Bouncing out of the bottom. Dropping fast into a straight arm loads the distal biceps tendon at its most vulnerable point. Sudden heavy eccentric loading is the classic mechanism for distal biceps tendon tears (AAOS, OrthoInfo). Fix: pause for a beat at the bottom.

• Seat set wrong. Shoulders shrug or the elbows drift off the pivot. Fix: armpits snug, elbows on the pivot, every time.

• Lifting the hips or shoulders. That is the body cheating the load up. Fix: pick a weight you can lower in two to three seconds on every rep.

• Curling the wrists. The forearms take over and the biceps lose tension. Fix: keep a straight wrist from start to finish.

How to Program the Machine Preacher Curl

Program the machine preacher curl as an accessory: 2 to 4 sets of 8 to 15 reps, one to two days per week, after your main lifts. Stop most sets one to three reps short of failure, and add reps across sets before you add load.

The numbers rest on solid evidence. Muscle growth responds to weekly volume (Schoenfeld et al., 2017a), training a muscle at least twice per week tends to beat once (Schoenfeld et al., 2016), and a wide range of loads builds muscle when sets are taken close to failure (Schoenfeld et al., 2017b; ACSM, 2009). Moderate reps suit this movement because the machine path makes clean high-effort sets easy and the elbows tolerate them well.

Keep it in perspective. Arms are not the priority in functional strength for military performance. Hinges, squats, pulls, presses, carries, and loaded movement carry the job, and the Army’s own fitness doctrine builds around them (Department of the Army, FM 7-22). The preacher curl belongs at the end of a strength workout for athletes, after the work that drives performance is done.

If you are deciding which overall plan to run, our guide to choosing a strength & endurance program walks through what to look for, from balancing lifting with running to how accessory work fits in.

Machine Preacher Curl Alternatives

The best machine preacher curl alternatives are the dumbbell preacher curl, the EZ-bar preacher curl, the cable preacher curl, and the spider curl. All four keep the upper arm in front of the body and the shoulder out of the movement.

Cable bicep exercises are the closest match to the machine’s constant tension, because the cable pulls along its own line rather than straight down. A cable preacher curl, or a low-pulley curl with the elbows held still, keeps load on the biceps near the top where dumbbells fade.

Preacher curl without a machine

No machine or preacher bench? Lie chest-down on an incline bench and curl dumbbells with your arms hanging straight (a spider curl). You can also kneel behind an adjustable bench with the backrest raised and drape one arm over it for a single-arm preacher-style curl.

Does Planet Fitness have a preacher curl machine?

Equipment varies by location. Many Planet Fitness clubs carry a selectorized arm curl machine built on a preacher-style pad, but not every club has one. Check the club’s equipment list in the app or call ahead. If it is missing, the cable and dumbbell alternatives above cover the same work.

FAQ: Frequently Asked Questions

What muscles does the machine preacher curl work?

The machine preacher curl works the biceps brachii, brachialis, and brachioradialis, with the forearm flexors holding the grip. Both biceps heads work, with a modest bias toward the short head because the pad flexes the shoulder. The fixed upper-arm position removes momentum, so the elbow flexors do nearly all of the work.

How do you set up and do a machine preacher curl?

Set the seat so your armpits sit snug on the top of the pad, line your elbows up with the pivot, and grip underhand. Curl without lifting your upper arms, squeeze at the top, then lower for two to three seconds. Stop just short of lockout and start the next rep without bouncing.

Machine vs. dumbbell preacher curl: which is better?

Neither is better overall. The machine gives a fixed path and more even tension through the range, which suits strict, repeatable sets. The dumbbell version trains each arm alone and exposes imbalances, but tension fades near the top. Research shows machines and free weights build similar muscle, so use whichever fits your goal.

Is the machine preacher curl good for beginners?

Yes. The machine preacher curl is one of the best bicep exercises for beginners because the pad and lever arm control the path. That leaves only seat height and elbow alignment to learn. Beginners can focus on full range and a controlled lowering phase without balancing a free weight.

How much weight should you use?

Use a weight you can lower in two to three seconds for 8 to 15 clean reps, stopping one to three reps short of failure. Stack numbers are not comparable between brands because cam designs differ, so log your load on the same machine and add weight once you hit the top of your rep range on every set.

How do you program preacher curls?

Program preacher curls as accessory work: 2 to 4 sets of 8 to 15 reps, once or twice per week, after your main lifts. Add reps until you reach the top of the range across all sets, then increase the load. For tactical athletes, preacher curls support pulling and grip but never replace compound strength work.

The machine preacher curl earns its place because it removes every variable but the curl: a fixed path, steady tension, and a pad that keeps momentum out of the set. Get the seat and elbow alignment right, own the bottom of the range, and treat it as the accessory it is.

Knowing the movement is the easy part. Building it into a week that also covers your strength, running, and rucking is where most athletes stall. Start a CF ONE plan and get your accessory work programmed around the lifts and standards that matter for your job.

References:

American College of Sports Medicine. Progression models in resistance training for healthy adults. Medicine & Science in Sports & Exercise. 2009;41(3):687-708.

American Academy of Orthopaedic Surgeons. Biceps Tendon Tear at the Elbow. OrthoInfo.

Department of the Army. FM 7-22, Holistic Health and Fitness. October 2020.

Haugen ME, Vårvik FT, Larsen S, Haugen AS, van den Tillaar R, Bjørnsen T. Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance: a systematic review and meta-analysis. BMC Sports Science, Medicine and Rehabilitation. 2023;15:103.

Marcolin G, Panizzolo FA, Petrone N, et al. Differences in electromyographic activity of biceps brachii and brachioradialis while performing three variants of curl. PeerJ. 2018;6:e5165.

Oliveira LF, Matta TT, Alves DS, Garcia MAC, Vieira TMM. Effect of the shoulder position on the biceps brachii EMG in different dumbbell curls. Journal of Sports Science and Medicine. 2009;8(1):24-29.

OpenStax. Anatomy and Physiology 2e. Section 11.5: Muscles of the Pectoral Girdle and Upper Limbs. Rice University; 2022.

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Pedrosa GF, Simões MG, Figueiredo MOC, et al. Training in the initial range of motion promotes greater muscle adaptations than at final in the arm flexors: a randomized controlled trial. International Journal of Environmental Research and Public Health. 2023;20(3).

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Schoenfeld BJ, Ogborn D, Krieger JW. Dose-response relationship between weekly resistance training volume and increases in muscle mass: a systematic review and meta-analysis. Journal of Sports Sciences. 2017;35(11):1073-1082. (Cited in text as 2017a.)

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Disclaimer: This content is for educational purposes only and is not medical advice. Consult a qualified healthcare provider before starting a new training program, especially if you have an elbow, shoulder, or wrist injury. Individual results vary, and no specific performance or physique outcome is guaranteed.