I'm a 4.0 NTRP mostly-spin-1HBH player. Everywhere around the internet I always got the same theory of tennis: exhale when doing any kind of stroke. Lately I got an idea to do it reverse on backhand and just tried it a few hours ago on court. The result was very positive: more power and stability, yet better at preserving stamina. The step-by-step idea is like this: 1. Exhale mildly in preparation. This allows chest to relax a little bit and bend forward nicely to make good preparation. On the contrary, inhaling makes chest a little stiffer, so bending forward is slightly more stressful on lungs. 2. Inhale when swinging a backhand. This may help the contractions of upper-back body and torso, easing body to straighten-up and rotate backward. Meanwhile, exhaling stiffen-up chest and lower-back, makes 1HBH relying more on hand and arm strength. The key to my successful experiment is I breathed calmly throughout the session. This allowed some room for preparation whether it would be deeper inhale (for FH) or exhale (for 1HBH). As for 2HBH, I don't think this breath technique is suitable because the swing power is mostly generated by the non-dominant hand which uses similar motion to forehand. Please, I'd like to hear your opinion about this theory, and I prefer you try it before.