A shift of 15 mm resulted in a difference in mean fat fraction which was on average 1-2% ranging up to 12% (p <0.01). Higher fat fractions were observed in distal and proximal muscle segments compared to the muscle belly in all muscles of the DMD subjects (p <0.001). Average fat fraction for a small central slice stack and a large coverage slice stack were compared to the value when the stack was shifted one slice (15 mm) up or down.
Mean fat fractions per muscle per slice for seven lower and upper leg muscles were compared between and within groups assuming a parabolic distribution. We studied fat replacement along the proximodistal muscle axis using the Dixon technique on a 3T MR scanner in 22 DMD patients and 12 healthy controls. The progressive replacement of muscle tissue by fat in Duchenne muscular dystrophy (DMD) has been studied using quantitative MRI between, but not within, individual muscles. Our results suggest that the use of garments with high compression intensity during exercise could exert a “mechanical protective effect”, which could therefore constitute an external strategy to tolerate a high training load or optimize the recovery process in multi-stage races. Wearing compression garments contributes to the attenuation of soft tissue vibrations which can reduce, at least in part, theĭeficit of voluntary activation level measured immediately after downhill running and improve the neuromuscular function during the recovery phase. The identification of muscular endurance as critical factor in the determination of performance leads to the second objective of the current thesis, based on the acute and delayed effects of wearing compression garments on neuromuscular function and energetic parameters during a short distance trail run or during intense eccentric exercise (i.e. The first objective was to characterize the physiological determinants of performance during short distance trail running races in a population of highly trained runners, using an experimental setting between laboratory protocols and an official event. Situated between "traditional" road races and ultra-trail races, limited research has focused on the analysis of short distance trail running. This thesis project aimed at improving scientific knowledge in the field of short distance trail running, a “booming” activity.