"Planet Fitness, a national chain, has a solid 'no-grunting' policy in place "Okay, so did they know what kind of business they were getting into here??
Why the heck would you open a fitness center that allowed body builders in and then tell them that they can't do what, for most, comes naturally without control??
Why not just put a big sign out side that reads "Girly Men only, Girly Girls too"....this is ridiculous.
When I was in college my weight training instructor told us to grunt, if we had to or if he couldn't hear us exhaling.
See the natural tendency when you are lifting weights is to hold your breath....well this is bad-it leads to hernias....to avoid those nasty things you need to breath while working the muscle in the direction you want it to developed (which is actually kind of silly, because muscles are like ropes--you can only pull with them you can't push, more in a bit). This releases chemicals in your muscles that makes them work more efficiently, not to mention that it keeps your body oxygenated.
But if you grunt when you exhale then your trainer or partner can hear that you are breathing. It goes hand & hand with working with weights, or at least it should if people are doing it right.
Don't like the grunting? Buy a home gym.....you never hear the pros bitch about it, just the wimpy ones who don't want to be reminded that they aren't putting their full effort into it.
Now about muscles...many people think you can push with muscles--after all you can push a box....push open a door...push a car.....whatever. But if you study the muscles and what they are doing you will find you aren't really "pushing" at all. When you push with your legs, what you are really doing is pulling with the muscles that surround your knee and your upper thigh (front quadriceps) muscles. The back of your legs are fairly mellow. Same thing when you walk....you will use the front of your thigh and the calf muscles, the muscles surrounding your ankles and your toes, the muscles in hips and your buttocks...but if you study them carefully you will find that when you step forward--your hip flexor muscles work but not your ass....at least on one side, it will be just the opposite for the muscles on the other leg which you are propelling backwards.
As you step downward the muscles on the top of the foot do the work, as you raise it up the calf muscles will do the work.
By knowing how muscles work you can find ways of exercising them with out having to do a lot of complicated things---even knitting can be good exercise--even if only for the wrists, fingers, arms, eyes. Oh yes---your eyes and your tongue are all muscles too...tongue exercises can be fun, do your work out with an ice cream cone! (heehee, I had a really devilish comment for this too but I won't put that one in...heehee)