Intramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength  in middle-aged and older men , particularly in the lower extremities
BACKGROUND Inconsistent fat-free mass ( FFM ) and muscle strength responses have been reported in r and omized clinical trials ( RCTs ) administering  testosterone replacement therapy ( TRT ) to middle-aged and older men .
Our objective was to conduct a meta- analysis to determine whether TRT improves FFM and muscle strength in middle-aged and older men and whether the muscular responses vary by TRT administration route .
Muscle mass, muscle strength, and muscle fat infiltration as predictors of incident mobility limitations in well-functioning older persons.
BACKGROUND Lower muscle mass has been correlated with poor physical function ; however , no studies have examined this relationship prospect ively . This study aims to investigate whether low muscle mass , low muscle strength , and greater fat infiltration into the muscle predict incident mobility limitation . METHODS Our study cohort included 3075 well-functioning black and white men and women aged 70 - 79 years participating in the Health , Aging , and Body Composition study . Participants were followed for 2.5 years . Muscle cross-sectional area and muscle tissue attenuation ( a measure of fat infiltration ) were measured by computed tomography at the mid-thigh , and knee extensor strength by using a KinCom dynamometer .  Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps . RESULTS Mobility limitations were developed by 22.3 % of the men and by 31.8 % of the women . Cox 's proportional hazards models , adjusting for demographic , lifestyle , and health factors , showed a hazard ratio of 1.90 [ 95 % confidence interval ( CI ) , 1.27 - 2.84 ] in men and 1.68 ( 95 % CI , 1.23 - 2.31 ) in women for the lowest compared to the highest quartile of muscle area ( p < .01 for trend ) . Results for muscle strength were 2.02 ( 95 % CI , 1.39 - 2.94 ) and 1.91 ( 95 % CI , 1.41 - 2.58 ) , p < .001 trend , and for muscle attenuation were 1.91 ( 95 % CI , 1.31 - 2.83 ) and 1.68 ( 95 % CI , 1.20 - 2.35 ) , p < .01 for trend . When included in one model , only muscle attenuation and muscle strength independently predicted mobility limitation ( p < .05 ) . Among men and women , associations were similar for blacks and whites . CONCLUSION Lower muscle mass ( smaller cross-sectional thigh muscle area ) , greater fat infiltration into the muscle , and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women . The association between low muscle mass and functional decline seems to be a function of underlying muscle strength
Intramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength  in middle-aged and older men , particularly in the lower extremities
BACKGROUND Inconsistent fat-free mass ( FFM ) and muscle strength responses have been reported in r and omized clinical trials ( RCTs ) administering  testosterone replacement therapy ( TRT ) to middle-aged and older men .
Our objective was to conduct a meta- analysis to determine whether TRT improves FFM and muscle strength in middle-aged and older men and whether the muscular responses vary by TRT administration route .