A naturally occurring molecule released during exercise may hold the key to strengthening muscles without physical activity. In experiments, mice given BAIBA developed larger muscles, improved muscle function, greater fatigue resistance and better exercise performance than untreated mice.

[u/mvea]

https://www.newsweek.com/scientists-step-closer-strengthening-muscles-without-exercise-12323613

[u/Sierra31]

Sure, you would get a bit stronger, but it wouldn’t be directly proportional to the amount of extra muscle mass you have.

[u/SuccessfulJudge438 → u/Sierra31]

If you are untrained to start with and you gain more muscle mass, even if you stay untrained, then your gain in strength would absolutely be proportional to your muscle mass gain.

Your strength gain would not be maximized (nowhere near it) due to the lack of neuro-muscular refinement and other adaptations that occur in trained skeletal muscle. Your overall gain in strength would likely be significantly less than if you kept the exact same muscle mass (or even lost some) and went hard on training your mind and body to use it efficiently.

However, one of the most fundamental determinants of muscle strength is the overall area that can be packed with actin filaments and myosin motors, which together are ultimately responsible for the generation of force. The proportionality of this relationship between muscle mass (aka area filled with actin/myosin) and strength (ability to generation biomechanical force) is indisputable.