Rear-delt fly (reverse fly)
Rear-delt flyes, on the reverse-fly machine or bent over with dumbbells, load the back of the shoulder more than rows do, but the evidence is limited to activation and modelling studies: we found no trial measuring rear-delt growth from them. On the machine, a neutral grip raised rear-delt activity over a palms-down grip.
What the science says
- A neutral grip raises rear-delt activity Moderate evidence
Schoenfeld et al. (2013) had 19 trained men do reverse-fly machine sets to failure: the neutral (palms-facing) grip produced more rear-delt and infraspinatus activity than the palms-down grip. Activation is not growth.
- More rear-delt force than rows (model) Limited evidence
Zhu et al. (2025) estimated, in a musculoskeletal model of 10 men, that the bent-over dumbbell lateral raise produced rear-delt forces similar to the face pull (about 58 N) and higher than the bent-over row (about 48 N). It is a computer estimate.
- Arms out at about shoulder height work the rear delts hardest Moderate evidence
Reinold et al. (2004) found that raising the arms out to the side at about 100° while lying face down, with full external rotation, produced the highest rear-delt activity (88% of maximum) of seven shoulder exercises in 10 healthy people.
How to do it
Muscles trained: posterior deltoid, infraspinatus, lateral deltoid
- On the machine, use the neutral (palms-facing) handles and set them at shoulder height
- With dumbbells, hinge until the torso is near horizontal and keep the back flat
- Lead with the elbows out to the side, keeping a slight bend
- Stop when the arms are in line with the body
- Lower slowly without swinging
How to apply it
Use light to moderate loads and higher reps, after your rows or presses.
Who should be careful
Low risk with light loads. The bent-over dumbbell version loads the lower back; use the machine or a chest-supported bench if that is a problem. Shoulder pain that persists is a reason to see a physician or physical therapist.
Frequently asked questions
Do rear-delt flyes grow the rear delts?
Very likely, but it has not been measured. The evidence is activation and modelling studies, which is why the grade is limited.
Which grip should I use on the reverse-fly machine?
Neutral, palms facing each other. Schoenfeld et al. found it produced more rear-delt and infraspinatus activity than a palms-down grip.
Are rows enough for the rear delts?
They load them less: Zhu et al.'s model estimated about 48 N of rear-delt force in the bent-over row versus about 58 N in the bent-over raise. Adding a few sets of rear-delt flyes or face pulls targets them more directly.
Scientific references
- Effect of hand position on EMG activity of the posterior shoulder musculature during a horizontal abduction exercise
- Biomechanical evaluation of posterior deltoid exercises and kinematic trajectory modeling
- Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises
More exercises
- Back squat Strong evidence
The barbell back squat reliably builds the quadriceps, glutes and adductors and is one of the best-studied lower-body exercises in training research.
- Front squat Moderate evidence
The front squat holds the bar on the front of the shoulders, which keeps the torso more upright and loads the knees less than the back squat while recruiting the thigh muscles about as much.
- Bulgarian split squat Moderate evidence
The Bulgarian (rear-foot-elevated) split squat trains one leg at a time and builds the quads and glutes with far less load on the bar than a back squat.
- Leg press Strong evidence
The leg press builds the quadriceps about as well as free-weight squats and also grows the glutes and adductor magnus, with no balance or spinal-loading limit.
- Hack squat (machine) Moderate evidence
The machine hack squat lets you squat deep on a fixed track with your back supported, which makes it easy to push the quads close to failure.
- Romanian deadlift Moderate evidence
The Romanian deadlift is a hip hinge that loads the hamstrings and glutes at long muscle lengths, and trials of stiff-leg deadlifts and similar hip-extension exercises show real hamstring growth, mainly in the semimembranosus and biceps femoris long head.