Dumbbell Fly (knees At 90 Degrees)

1. Lie back on a flat bench holding a dumbbell in each hand above your chest, palms facing each other.
2. Bend your knees to about 90 degrees and plant your feet flat on the bench or floor for stability.
3. Start with your arms extended and a slight bend in your elbows.
4. Brace your core and lower the dumbbells out to your sides in a wide arc.
5. Continue until you feel a stretch across your chest, keeping the slight elbow bend fixed.
6. Reverse the motion, bringing the dumbbells back together above your chest.
7. Squeeze your chest at the top before starting the next rep.

Common Mistakes

• Bending the elbows too much: Turning the fly into a press by bending the elbows heavily shifts the work onto the triceps. Keep a slight, fixed bend throughout the movement.
• Lowering the dumbbells too far: Dropping below chest level places excess stress on the shoulder joint. Stop once you feel a full stretch across the chest.
• Pressing the dumbbells together too hard at the top: Clanking the dumbbells together removes tension right at the peak contraction. Bring them close without touching and squeeze the chest instead.
• Using momentum to swing the weights: Letting the dumbbells drop quickly and bounce back up skips the controlled chest contraction. Lower and raise the weights at a steady, deliberate pace.

Programming Tips

Place this fly after your pressing work on chest day, doing 3 to 4 sets of 10 to 15 reps with 60 to 90 seconds rest. The bent knee setup flattens the lower back against the bench, which keeps the ribs down and turns the movement into a strict chest isolation exercise that loads the pecs in the stretched position where growth is best stimulated.

Lie back, pull your feet up until the knees sit at 90 degrees, and press the lower back into the bench before raising the dumbbells. Start with 6 to 10 kg per hand and add 2 kg only when the top rep of every set still ends with a hard chest squeeze. The most common fault is lowering the dumbbells too deep in search of a stretch, which pushes the shoulder joint past where the pecs can protect it, so stop when your upper arms are level with the bench and keep the slight elbow bend fixed from the first rep to the last.

Common Questions

Why do a dumbbell fly with knees at 90 degrees?

Bending the knees and planting the feet tilts the pelvis back and removes the lower back arch most people use on a bench. That keeps the chest doing the work and limits how far the elbows can drop, which protects the shoulders.

Dumbbell fly vs dumbbell press, which is better for chest?

The press builds more total chest strength and size because it allows heavier loads. The fly is an isolation movement that adds stretch and a strong peak contraction, so use it after presses rather than instead of them.

How heavy should dumbbell flies be?

Lighter than you think: 6 to 10 kg per hand for most beginners, and 14 to 20 kg for experienced lifters. If you have to bend the elbows to lift the weight, it is too heavy for a fly.