Twice last week, I met new clients whose voice problems traced back to the time they had started serious weight-training. I've seen others who got sudden lesions, including one nasty vocal hemorrhage, when they changed trainers or otherwise increased their workout intensity.
Most voice problems have several contributing reasons so I won't argue for an exact correlation. But when this is the only thing that fits the same time-frame as the beginning of a voice problem, it does make me suspicious. You CAN have a buff body and a clear, flexible, pain-free voice. You just have to be smart about both.
Vocal mechanics review: besides making sound, the vocal cords work as a valve in your airway. For instance, they open extra-wide during aerobic exercise to help you manage bigger amounts of air. And they close tightly to valve-off the airway when you lift something heavy (as well as whenever you swallow).
A dumbbell, a suitcase or a big screen TV if it's hard to move, you'll hold your breath for an instant. It's a reflex that makes your torso more stable, better able to push & pull. Try it.
Now, fitness trainers routinely tell people not to hold their breath DURING the lift. This is appropriate, standard advice to avoid serious problems like a stroke or blackout. At my gym, most people exhale dutifully on the exertion, & inhale on recovery.
The problem I have with strength training for singers and other voice pro's is the moment before the lift. Most people hold their breath to seal the ribcage closed & firm while getting into position. This means that in the last split-second when you brace yourself and get ready to push, your vocal cordsitty-bitty muscles about a centimeter long, held closed by even tinier ones are being asked to help manage that 50, 100, or 300 lb weight.
Then when you do exhale, the pressure in your lungs & ribcage is suddenly released. Even if you don't grunt or yelp, air blasts through your voice box like a hockey player bursting through a double-flap kitchen door. The cords are blown apart and their edges get a little roughed up. During an hour-long routine, that explosive burst can happen 100 times or more!
Rough edges make rough sound. Repeatedly squeezing the cords together and then blasting them apart can lead to vocal cord callouses (nodules) or worse.
So if you're serious about protecting your voice: pay attention BEFORE you lift. As a singer, if you have to hold your breath at all while bracing to get into position, you're using too much weight.
See what happens if you drop your weights down as far as necessary to be able to breathe smoothly throughout the routine. To stay at the same intensity for your fitness goals, increase the rep's, or vary your tempo, such as lowering the weights very slowly.
Pay attention also to the end of each exercise. If you're "working to fatigue," the moment you are absolutely tempted to hold your breath is the cut-off! That's when the targeted muscles are already fatigued, & are calling on your vocal muscles to help.
BTW, here's what some other voice coaches have written about the combination of weight training and voice. I don't disagree, I just don't think they go far enough.
The Singer's Companion, by Sharon Stohrer
My comments on other exercise activities are in the free online excerpt of my book.
PS If there's a steam-room where you work out, use it! Without talking.