At least half of trainers make this mistake when doing cable flyes for the chest: pressing them instead of using a flye (arc-like) motion. Here’s why that’s a problem.
Well, technically it’s not a mistake. You’re certainly welcome to press your cable crossovers (that is, bending and extending at both the shoulder and elbow joints instead of just the shoulder when done correctly). But, because you’re standing and not lying against a flat bench (or any angled bench), you lose a whole lot of force generation. (Want an example? Google “shoot a cannon out of a canoe.”) Bottom line: you’ll sacrifice a ton of weight, because your body isn’t supported, making this version of a press wholly inferior to doing the same movement on a bench.
If you want to do presses, fine. Do them on benches and first in your training. The cable crossover is a single-joint movement that better isolates the pecs – that’s its intention – most often done after your multi-joint presses.
Here’s what to watch for: the degree of bend in your elbows at the start must be exactly the same as the degree of bend at the finish! Lock a 135-degree or so bend in your elbows and you must maintain that bend throughout the entire set. No extending your elbows (bending, then straightening your arms on each rep)! You’ll have to sacrifice on the load you’re using, but you’ll better isolate the pecs and remove the triceps from the equation.
