Figure 1.

Optogenetic activation of triceps surae muscle group is not invasive and does not impact weight gain or generated isometric ankle joint torque in Young mice. (A) Young mice, regardless of exposure to daily bouts of optogenetic muscle stimulation (5- or 20-minute duration), gained weight for the duration of the experiment. However, adult mice lost weight from onset to end of the experiment. (B) Normalized torque significantly increased in adult but not young mice with daily bouts of 20-minute optogenetic muscle stimulation. Each data point denotes average weekly change in generated ankle torque normalized to weight of the animal. (C) The steady state generated torque at the end of the 20-minute loading bout, measured during isometric ankle plantarflexion, was ~30% of the peak force in young mice for the first week of daily optogenetic muscle loading. Error bars: Mean ± SD (*: p< 0.05, **: p< 0.001, ****: p < 0.0001, and ***: p = 0.0004).