So many people talk about theories. Others study them. You are actually running your own experiment to test your theory. That's awesome. While there is some research on the relationship between physical fitness/exercise and stuttering., I don't know any research suggesting fitness is detrimental for stuttering. In voice therapy we might consider the impact of excessive "grunting" and "locking" in the throat - common in some tennis players and lifters. But I have not seen any evidence of lifting leading to more stutter. If anything, I think there's lots of good evidence of physical fitness (well-rounded, including aerobic fitness, i.e. running) leading to gains in other areas. Not necessarily "fluency" but mental- emotional-wellbeing, neurological health (BDNF and more), adaptability, discipline, and cardiovascular, respiratory health. All "good" things. Of course, if someone finds that lifting is hurtful to them, or leads to negative outcomes, they should use their judgement. \*Here's an old research article from '68, but useful to see the abstract: **Effects of Physical Training on Stuttering** Authors: [B. Don Franks](https://pubs.asha.org/doi/10.1044/jshr.1104.767#con1) and [Elizabeth B. Franks](https://pubs.asha.org/doi/10.1044/jshr.1104.767#con2) Publication: Journal of Speech and Hearing Research Volume 11, Number 4 [https://doi.org/10.1044/jshr.1104.767](https://doi.org/10.1044/jshr.1104.767)[Get Access](https://pubs.asha.org/doi/10.1044/jshr.1104.767#core-collateral-purchase-access) # Abstract Eight college students enrolled in group therapy for stuttering were divided into two equal groups for 20 weeks. The training group supplemented therapy with endurance running and calisthenics three days per week. The subjects were tested prior to and at the conclusion of the training on a battery of stuttering tests and cardiovascular measures taken at rest, after stuttering, and after submaximal exercise. There were no significant differences (0.05 level) prior to training. At the conclusion of training, the training group was significandy better in cardiovascular response to exercise and stuttering. Although physical training did not significantly aid the reduction of stuttering as measured in this study, training did cause an increased ability to adapt physiologically to physical stress and to the stress of stuttering.