This is a great exercise if your delts tend to take over when you train chest.

Manual Resistance Flyes

1. Set a bench on a low incline. With a pair of moderately heavy dumbbells, do a set of strict dumbbell flyes, gradually going deeper into the bottom stretch with each rep. Don't force this stretch; let your range of motion extend on its own.
2. At failure, drop the dumbbells and grab a lighter pair of dumbbells. Continue performing strict reps, except now have your partner gently push down on your elbows as you lower the weight, forcing you to fight the resistance. At the bottom of the rep, make sure your partner stops pushing. You don't want extra resistance in this highly fragile part of the rep.
3. Return to the top position and repeat the process. Your partner should adjust how much he pushes based on your level of fatigue, so be sure to choose your training partner wisely. A college kid with one eye on his iPhone and the other on his eleven-teen inch guns would not be a suitable fit.

Expect to be gassed surprisingly quickly. If not, your partner went too easy on you. Have him step it up on the next set. What makes this exercise better than flyes with chains, bands or cables is that your partner can adjust the resistance mid-rep. There's no need to stop, fiddle with the equipment, dig up a half-pound plate, etc. He just pushes down with more or less resistance.

When to Do Them

Manual resistance flyes are best performed after your pressing work on chest day.