Bone Marrow Adipose Tissue Content Changes In Men And Women Following 24-weeks Of Exercise Training

High BMAT is associated with low bone mineral density and increased fracture risk. Exercise training reduces BMAT in animals however, longitudinal human research is lacking. PURPOSE: This study investigated the effects of 24 weeks of ballistic resistance training on BMAT in the lumbar vertebra and distal tibia of men and women. METHODS: Healthy, recreationally active men and women, 18-40 years old (n = 75; 33 men, 42 women) completed 3 supervised resistance training bouts and 3 lower body plyometric bouts per week for 24 weeks. Pre- and post-intervention, single-voxel 1H-MRS data of the 4th lumbar vertebra and the distal tibia metaphysis were acquired via a point-resolved spatially localized spectroscopy (PRESS) pulse sequence without water suppression. A custom fitting algorithm for bone marrow analysis estimated all lipid signals combined (0.9, 1.3, and 1.6 ppm) which were scaled to the unsuppressed water peak (4.7 ppm) and expressed as a lipid to water ratio. To determine if training altered lumbar and tibial BMAT content and if BMAT changes differed between sexes (sex x time) mixed methods ANOVAs were used to analyze pre- to post-intervention BMAT changes. For all analyses, α = 0.05. RESULTS: : Lumbar BMAT demonstrated no significant sex x time interaction (p = 0.963). A significant main effect for time was observed suggesting a 10.8% decrease in lumbar BMAT across both sexes (p < 0.001; Pre: 0.65 ± 0.36, Post: 0.58 ± 0.32). Lumbar BMAT decreased ~8.5% in men and ~ 13.5% in women, but this difference in BMAT change between sexes was not significant. In contrast, training had no effect on tibial BMAT (main effect for time: p = 0.573; Pre: 21.81 ± 4.77, Post: 21.48 ± 4.78). CONCLUSIONS: Resistance training decreased BMAT content in the lumbar vertebra, but not the distal tibia in men and women. Past research has identified two possible BMAT subtypes; constitutive BMAT which is resistant to nutritional and hormonal changes and regulated BMAT which exhibits greater plasticity. Constitutive BMAT is more prominent in the distal tibia whereas regulated BMAT is more prominent in the lumbar vertebrae. Thus, our findings support previous research and identify resistance exercise as an additional factor which differentially influences constitutive and regulated BMAT. Supported by: UK Ministry of Defence WGCC 5.5.6-Task 0107