Rear deltsMachineBeginner

Rear Delt Machine: The Ultimate Guide

By Bryan Alger, Co-Founder of Gravitus

ยท Updated Sep 30, 2026

The rear delt machine, or reverse pec deck, is a seated fly done facing the pad. With the handles at shoulder height and a slight elbow bend, sweep your arms back until they line up with your body. It trains the rear delts, with the middle traps and rhomboids helping. Most lifters do 3 sets of 10 to 15 reps.

Sets x reps 3 x 10-15
Median 10-rep weight 10045 lbkg men 4520 lbkg women
Muscles Rear delts, mid traps, rhomboids
Setup Handles at shoulder height
Rear Delt Machine start and squeeze positions
  1. 1Start. Chest on the pad, seat set so your arms are level with your shoulders. Hold the handles in front of you with a slight bend in your elbows.
  2. 2Squeeze. Sweep your arms out and back until they line up with your body, pause for a second, then let them come forward under control.
Watch 3 video demonstrations
Video 1 of 3

Find more video demonstrations in the Gravitus app

Technique

How to use the rear delt machine

  1. Set the seat so the handles sit at shoulder height. With your chest on the pad and your arms reaching forward, your arms should be level with the floor.
  2. On a combined pec deck, move the arms to their front position with the start lever, so the handles begin close together in front of your chest.
  3. Sit facing the pad with your chest against it and your feet flat. Take the handles with a slight bend in your elbows and keep that bend for the whole set.
  4. Sweep your arms out and back in a wide arc until they line up with your body. Pause for a second.
  5. Let the handles come forward over 2 to 3 seconds, until you feel a stretch across the back of your shoulders, without letting the plates touch.
Setup

Grip, arm height and elbow bend

Thumbs upVertical handlesDrew slightly more rear delt activity than palms down on a reverse fly machine. The rotator cuff works harder too.
Palms downHorizontal handlesThe grip Life Fitness shows for its rear deltoid setting. A band study found it drew the most rear delt activity, so either grip works.
Arm heightLevel with your shouldersThis changes more than grip. Arms that travel higher than your shoulders bring the traps in, so set the seat to keep them level.
Elbow bendSlight and fixedMore bend shortens the lever, so the same pin feels lighter. Bending and straightening mid-rep turns the fly into a row.

Grip makes a small difference, and the studies disagree on its direction. On a reverse fly machine, trained men drew 90% of their maximum rear delt activity with a thumbs-up grip and 87% with palms down, a small but significant gap, and the infraspinatus worked harder with thumbs up (Schoenfeld 2013). In a band pull-apart study, palms down drew the most rear delt activity, and grip did not change middle trap activity (Fukunaga 2022). The path of your arms mattered more there: level and upward pulls both drew about 30% more middle trap activity than a downward pull, while the rear delts did not change significantly (Fukunaga 2022). On the machine, the seat sets that path. Use the grip your machine has or the one that feels better, and spend your attention on seat height.

Range of motion

How far back to go

Stop when your arms line up with your body. That is where each rep ended in the reverse fly machine study (Schoenfeld 2013).

The rear delts move your upper arm. The middle traps and rhomboids move your shoulder blades. Past the line of your body, more and more of the movement comes from pinching your shoulder blades together, so that last part of the rep is mostly upper back work. Both are useful; decide which one you are training.

At the front of the rep, let the handles come forward until you feel a stretch across the back of your shoulders, while your chest stays on the pad.

Rear delts or upper back?

For rear delts, keep your arms level, let your shoulder blades stay wide and stop with your arms in line with your body. For the upper back, finish by pinching your shoulder blades together and hold for a second.

Gravitus data

How much weight should you use on the rear delt machine?

On Gravitus, the median man lifts 100 lb (45 kg) for 10 reps on the rear delt machine, and the median woman 45 lb (20 kg).

Men, typical 100 lb for 10 reps
Most lift
75 to 130 lb
Top 10% lift
160 lb or more
Starting out
under 75 lb
Women, typical 45 lb for 10 reps
Most lift
35 to 60 lb
Top 10% lift
75 lb or more
Starting out
under 35 lb
Men, typical 45 kg for 10 reps
Most lift
35 to 60 kg
Top 10% lift
72.5 kg or more
Starting out
under 35 kg
Women, typical 20 kg for 10 reps
Most lift
16 to 27.5 kg
Top 10% lift
35 kg or more
Starting out
under 16 kg
PercentileMenWomen
25th100 / 75 lb45 / 35 lb
Median135 / 100 lb60 / 45 lb
75th175 / 130 lb80 / 60 lb
90th215 / 160 lb105 / 75 lb
 One-rep max / 10-rep weight, rounded to 5 lb (2.5 under 40). From 13,439 men and 2,912 women who log the rear delt machine on Gravitus, computed Oct 4, 2026 (Brzycki). Methodology
PercentileMenWomen
25th45 / 35 kg20 / 16 kg
Median60 / 45 kg27.5 / 20 kg
75th77.5 / 60 kg37.5 / 27.5 kg
90th97.5 / 72.5 kg47.5 / 35 kg
 One-rep max / 10-rep weight, rounded to 2.5 kg (1 under 20). From 13,439 men and 2,912 women who log the rear delt machine on Gravitus, computed Oct 4, 2026 (Brzycki). Methodology
Rear delt machine numbers do not compare between gyms. Each brand gears its stack through different cams and arm lengths, so the same pin can feel much heavier on one machine than on another. On most machines the pin is the load for both arms together. Compare yourself to your own log on the same machine, grip and start setting.
Anatomy

Rear delt machine muscles worked

Rear delts (posterior deltoid)Pull the upper arm out and back. Trained men drew about 90% of their maximum rear delt activity on a reverse fly machine (Schoenfeld 2013).
Primary
Middle and lower trapsPull the shoulder blades together and down. Moving the arm back with the thumb turned up drew the highest middle trap activity of 10 exercises (Ekstrom 2003).
Secondary
RhomboidsWork with the middle traps, most at the end of the rep when your shoulder blades pinch together.
Secondary
Infraspinatus and teres minorTurn the arm out and steady the shoulder. A thumbs-up grip drew more infraspinatus activity than palms down (Schoenfeld 2013).
Secondary
Side delts, coreThe side delts help hold your arms at shoulder height. Your core keeps your chest on the pad.
Stabilizer
Research

What the research says about the rear delt machine

  • "Palms down isolates the rear delts, and thumbs up shifts the work to the traps." Neither study backs this. On the machine, thumbs up drew slightly more rear delt activity (Schoenfeld 2013). With a band, palms down did, and grip did not change middle trap activity at all (Fukunaga 2022).
  • "Squeeze your shoulder blades together to hit the rear delts." The rear delts move the arm, not the shoulder blades. A hard squeeze at the end trains the middle traps and rhomboids, which is useful, but it is upper back work.
  • "The rear delts need the stretch loaded." Over 10 weeks of reverse fly machine training, the rear delts grew with the machine set hardest near the stretch or hardest near the squeeze, with no difference between the two (Jones 2025, a preprint not yet peer reviewed).
  • "The rear delts are slow-twitch, so they need high reps." No study we found shows this. Sets taken close to failure build muscle across a wide range of reps (Schoenfeld 2021), and the 10-week study used 8 to 12 (Jones 2025).
Compare

Rear delt machine vs cable reverse fly vs dumbbell rear delt fly

Rear delt machineCable reverse flyDumbbell rear delt fly
Hardest pointSet by the machineSet by pulley height and stanceAt the top, nothing at the bottom
Balance neededNone, chest on a padSome, standingMost, bent over
AnglesOne fixed pathHigh, mid or low pulleyHow far you bend over
Best forTaking sets to failure safelyChoosing the angle, one arm at a timeTraining without a machine
Verdict

No study has compared the three for growth. The machine is the easiest to set up the same way every week, and 10 weeks of reverse fly machine training grew the rear delts in new lifters (Jones 2025). Use the cable or dumbbell version when the machine is taken.

Programming

Rear delt machine sets, reps and progression

3Sets
10-15Reps
0-2Reps left

Stop each set 0 to 2 reps short of failure. Sets taken close to failure build muscle across a wide range of reps (Schoenfeld 2021), so 10 to 15 is a range, not a rule. In the 10-week study, 4 to 5 sets of 8 to 12 reps to failure, twice a week, grew the rear delts (Jones 2025).

Do the rear delt machine near the end of a pull or shoulder day, or first if your rear delts lag.

Add reps before weight. Stack jumps are big for a small muscle. When every set reaches 15 with the same seat and start setting, move up one plate and drop back to 10.

Form

Common mistakes

Variations

Rear delt machine variations

Single-arm rear delt machineOne side at a time, which evens out a weak side. The 10-week study trained each arm this way (Jones 2025).
Cable Reverse FlyTwo pulleys instead of a pad, so you choose the angle.
Bent-over dumbbell rear delt flyBent over with dumbbells. Hardest at the top, nothing at the bottom.
Chest-supported dumbbell rear delt flyChest on an incline bench, so your lower back rests.
Face PullA rope to your face on a high pulley, elbows high. Adds more outward rotation.
Pec DeckThe same machine facing the other way. Trains the chest.
FAQ

Questions people ask

What does the rear delt machine work?

The rear delts, with the middle traps, rhomboids and rotator cuff helping. The side delts hold your arms up and your core keeps you on the pad.

Is rear delt machine push or pull?

Pull. You pull your arms out and back, and the rear delts and upper back do the work, so it fits on pull day or shoulder day.

Does rear delt fly work traps?

Yes, the middle and lower traps. Moving the arm back with the thumb up drew the highest middle trap activity of 10 exercises (Ekstrom 2003). A seat set too low, or pinching your shoulder blades at the end, gives the traps more work.

What is the best grip for the rear delt fly machine?

Either. On the machine, thumbs up drew slightly more rear delt activity (Schoenfeld 2013); with a band, palms down did (Fukunaga 2022). Seat height changes more than grip.

How do you adjust the rear delt machine?

Set the seat so the handles sit at shoulder height and your arms are level with the floor. On a pec deck, move the arms to their front position so the handles start together in front of your chest.

Is rear delt shoulder or back?

Shoulder. The rear delt is the back part of the deltoid. The rear delt machine trains it together with the upper back, so it fits on either day.

How much weight should I use on the rear delt machine?

For 10 reps, the median on Gravitus is 100 lb (45 kg) for men and 45 lb (20 kg) for women. The strongest quarter lifts 130 lb (60 kg) and 60 lb (27.5 kg) or more.

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References
  1. Schoenfeld et al. 2013. J Strength Cond Res 27(10):2644-2649.
  2. Fukunaga et al. 2022. Int J Sports Phys Ther 17(3):400-408.
  3. Ekstrom, Donatelli and Soderberg 2003. J Orthop Sports Phys Ther 33(5):247-258.
  4. Jones et al. 2025. SportRxiv preprint, not peer reviewed.
  5. Schoenfeld et al. 2021. Sports 9(2):32.
  6. Life Fitness. Insignia Series owner's manual, Pectoral Fly / Rear Deltoid.