“…Mice have a strong intrinsic drive to run large distances in their active phase (De Bono et al, 2005), which keeps stress and mouse handling at a minimum. Furthermore, by applying resistance to the running wheel, muscle hypertrophy can be induced without substantial muscle damage (Cornelison, 2018;Legerlotz et al, 2008;Mccarthy et al, 2017;Murach et al, 2018;O'Connor et al, 2007;Soffe et al, 2016;White et al, 2016) and reducing wheel resistance (free running) leads to favorable endurance adaptations without pronounced effects on muscle hypertrophy (Jackson et al, 2015;Manzanares et al, 2019). Thus, using this exercise model in combination with genetic lineage tracing experiments of SCs, we aimed to evaluate whether SC contribution to myonuclei is mediated by increasing load during exercise training and whether this manifests in SC-mediated myonuclear accretion.…”