Myostatin inhibition in adults does not consistently improve measurable physical function.

Study: Inhibition of myostatin does not ameliorate disease features of severe spinal muscular atrophy mice.

Blocking myostatin didn't help sick mice move better, which suggests it might not make people stronger or more mobile either—even if it builds muscle.

Study: Myostatin Inhibition-Induced Increase in Muscle Mass and Strength Was Amplified by Resistance Exercise Training, and Dietary Essential Amino Acids Improved Muscle Quality in Mice

Blocking myostatin made mice muscles bigger, but didn't always make them stronger or better at physical tasks—unless they also exercised or got special nutrients. So just blocking myostatin doesn't reliably make adults perform better.

Study: Myostatin deficiency blunts mechanical adaptation of soleus muscle to overload

When scientists blocked a protein called myostatin in mice, the muscles didn’t get stronger when they were exercised — even though they got bigger. This suggests that just blocking myostatin doesn’t make muscles work better, which supports the idea that it doesn’t reliably improve physical performance.