Over a decade ago I became TRX certified, and I remember being taught the TRX push-up as part of the exercise repertoire, at the time the exercise felt awkward but I could not logically explain why.
As I became more educated in biomechanics, I realized the problem, the anatomical function of pectoral muscle is to adduct the humerus towards midline, the TRX push-up, because of the TRX design with the straps diverging from each other from a single anchor point, it requires that you abduct to stabilize, and the muscular stress is on the anterior deltoid and triceps, not the pecs.
It is not a proper push-up, it is a weird motion because you would never ordinarily press this way, the reciprocal inhibition requires the pecs to deactivate during the movement, not to contract.
If you are going to do a suspended push-up, use rings, ring push-ups are fantastic, they build strength, they build muscle, and and you can progress them over time.
