Reckonerreckoner.fit Open Reckoner Create your account
Shoulder isolation · Machines and cables

Machine rear delt fly

The pec deck turned around. You face the pad with your chest against it and sweep the handles back and out, which asks the back of the shoulder and the upper back to do work a press almost never gives them3. The chest pad also holds you in place, so the set is about the arms moving wide and nothing else.

Chest on the pad, sweep the arms back wide.

The cue Reckoner puts on your wrist mid set.
Pattern
Shoulder isolation
Trains
Rear delts, upper back
Kit
Machine pec deck
Loading
A weight you choose
Reckoner prescribes
3 sets of 12 to 15 reps at RPE 8
Progression step
5 kg once the top of the range is clean
Skill
Simple to learn
Recovery cost
Very low

Muscles worked

Primary
Rear delts · Upper back
Secondary
Traps

How to do it

  1. Face the pad and set the handles at shoulder height

    Sit facing the pad with your chest against it and raise the seat until the handles are level with your shoulders. Handles set too low turn the sweep into a pull toward the hips.

  2. Keep a soft bend in the elbows

    Hold the same small bend through the whole rep. If the elbows bend more as the set gets hard, you are rowing the handles, not sweeping them.

  3. Sweep the arms back and out

    Move the handles in a wide arc until your arms are level with your back, and keep your chest on the pad. Stop when your hands are in line with your shoulders.

  4. Return slowly to a long arm

    Let the handles come back until your arms are almost in front of you, and keep a little tension on the stack at the end. Let the arms get as far as the machine allows without letting the stack rest.

What goes wrong

How Reckoner progresses this lift

Six weeks of this lift, run through the real engine. Nothing below was typed in: the prescription, the decision and the sentence beside it all come from the same code that writes your week.

Machine rear delt fly, six weeks
WeekPrescribedWhat it did
13 x 12More reps 12 → 13 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does.
23 x 13More reps 13 → 14 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does.
33 x 14More reps 14 → 15 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does.
43 x 15Load up — → 5 kgYou hit the top of the range with three reps left in the tank (RPE 7), so the weight on the machine goes up 5 kg to 5 kg. The weight went up, so the reps come down to twelve. You are now working 12 to 15.
53 x 12 at 5 kgDeload 40% of sets offFive weeks of building, then one week lighter. About 40% of the sets come off. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue.
62 x 12 at 5 kgMore reps 12 → 13 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to three sets.

Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.

The full rule, and why the reps move before the load does, is in how Reckoner decides to add weight.

Questions people ask

Which muscles does a rear delt fly work?

In a study of 29 men and women doing reverse flyes with dumbbells and bands, the posterior deltoid was the muscle the exercise is aimed at, with the middle deltoid and the upper trapezius measured as helpers1. In a separate study of 30 healthy people across ten exercises, shoulder horizontal extension with the arm turned outward gave the highest activity in the middle trapezius, which is part of the upper back2.

Does a press already train the back of the shoulder?

Very little. In 13 men lifting at 60 per cent of a maximum, the posterior deltoid worked at about 3.5 per cent of its maximal activity in the bench press and about 11 in the shoulder press, against about 24 in the lateral raise3. If you want it trained on purpose, it needs a movement of its own.

Will Reckoner put this machine in my plan?

Not by itself, and on purpose. The engine never places this machine for you: you reach it by choosing it in a swap or in the movement picker. It sits in the same swap group as the seated reverse dumbbell fly, so one can stand in for the other, and a lane you have put it on keeps it.

Similar movements

Reckoner eases the load first when this lift stalls, and offers one of these only if it stalls again after that. A lift already as light as your kit goes has no load left to ease, so the offer comes straight away. Each of them has a page.

Face pullIncline reverse flyProne Y raiseReverse cable crossoverSeated reverse dumbbell fly

Sources

  1. Bergquist and colleagues, Journal of Human Kinetics, 2018. Muscle activity in upper-body single-joint resistance exercises with elastic resistance bands vs. free weights 29 men and women doing flyes and reverse flyes with bands and dumbbells, with the posterior deltoid as the muscle the reverse fly is aimed at and the middle deltoid and upper trapezius measured as ancillary muscles
  2. Ekstrom and colleagues, Journal of Orthopaedic and Sports Physical Therapy, 2003. Surface electromyographic analysis of exercises for the trapezius and serratus anterior muscles 30 healthy people across ten exercises, with shoulder horizontal extension with external rotation among the two highest for the middle trapezius. This is a 2003 study and the standard reference on the question
  3. Campos and colleagues, Journal of Human Kinetics, 2020. Different shoulder exercises affect the activation of deltoid portions in resistance-trained individuals 13 men experienced in strength training lifting at 60 per cent of a maximum, with posterior deltoid activity about 3.5 per cent in the bench press, 11.4 in the shoulder press and 24 in the lateral raise