Pec Deck
Also known as: pec dec, chest fly machine, butterfly machine
For pure chest isolation with zero setup skill required, the pec deck is hard to beat. The machine locks your body in place and guides the arc, so every ounce of effort goes into squeezing the pecs together. Lifters use it to finish a chest session with high-rep burnout work, or early on as a pre-exhaust before pressing when the triceps usually give out first.
How to do the pec deck, step by step
- Set the seat so the handles or pads sit at mid-chest height when you grip them.
- Adjust the arm start position so you feel a comfortable stretch, not a strain, at the back.
- Sit with your back flat against the pad, feet planted, and chest lifted.
- Grip the handles with a soft bend in the elbows and bring them together in front of your chest.
- Squeeze the pecs hard for a full second when the handles meet.
- Let the arms open back up slowly over two to three seconds, stopping at a deep but pain-free stretch.
Form cues that fix most reps
Touch your pecs with your mind before the set — the goal is to feel them close the machine, not the arms.
Keep your shoulder blades pinned to the pad; if they roll forward, the front delts steal the work.
Pause every rep at the middle — the squeeze is the whole point of this machine.
Common mistakes (and the fix)
Pec Deck sets and reps
Match the rep range to your goal, not the other way around. These are the standard evidence-based ranges:
| Goal | Sets × Reps | Rest |
|---|---|---|
| Strength | 3–5 × 3–6 | 2–3 min |
| Muscle growth | 3–4 × 8–12 | 60–90 sec |
| Endurance | 2–3 × 15–20 | 30–60 sec |
How our free programs prescribe it
Pec Deck FAQ
What muscles does the pec deck work?
The pec deck isolates the chest — mostly the middle fibers, with some upper-chest involvement — while the front delts contribute a little. The triceps are almost completely removed, which makes it a true chest isolation exercise.
How many sets and reps on the pec deck?
Do 3 sets of 12–15 reps with a one-second squeeze at the middle of each rep. It shines at higher reps taken close to failure, since the machine makes failing safe.
Is the pec deck safe for my shoulders?
Generally yes, as long as you set the start position sensibly. Problems come from forcing an extreme stretch behind the body. Set the range so you feel the stretch in the chest, not the front of the shoulder, and build depth gradually over weeks.
More chest exercises
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