a) Representative image of a mouse during a gait analysis (top) and the gait footprints collected during the analysis (bottom). Mice were positioned in a transparent treadmill and a camera was positioned underneath to record the gait. ( b) Quantification of the gait ‘disability score’ resulting from the analysis of 47 parameters (see Methods) ( n=6). ( c) In vivo force production measurements of TA muscles treated with bioconstructs following VML injury in non-exercised or exercised mice. After 30 days, the distal tendons were attached to a force transducer and contractions were induced through sciatic nerve stimulation ( n=6). ( d) Ex vivo force production measurements from non-exercised or exercised mice. The same muscles measured in c were then dissected and cultured in a chamber. The distal tendons were attached to a transducer and contractions were induced electrically in the culture bath ( n=6). ( e) (Left) Representative IF image of transplanted bioconstruct. Yellow arrows indicate donor-derived (eYFP +) myofibres with NMJs (αBTX +) within regions of the transplanted bioconstruct. (Right) Higher magnification of an NMJ associated with a donor-derived myofibre (scale bars=50 μm). ( f) Quantification of NMJs in whole cross-sections of transplanted bioconstructs along 3 mm lengths of TA muscles. Muscles were either uninjured and exercised (‘-VML, +Ex’) or subjected to VML injury and bioconstruct treatment (‘+VML, +Tx’) without (‘-Ex’) or with (‘+Ex’) exercise ( n=5). ( g) (Larger panels) Representative IF images of myofibres with mature NMJs (αBTX + and also stained positive for Synaptophysin (SynPh) and Neurofilament (NFL)) within regions of transplanted bioconstructs (scale bar=100 μm). (Smaller panels) Higher magnification of a mature NMJ (scale bar=10 μm). ( h) Quantification of mature NMJs in whole cross-sections of uninjured muscles or of injured muscles with transplanted bioconstructs along 3 mm lengths of TA muscles characterized as in f ( n=4). Data are±s.e.m. For statistical analysis, t-tests were used. ** P<0.001; **** P<0.00001.