Effect of timing of meal intake after squat exercise training on bone formation in the rat hindlimb

We hypothesized that bone acquisition was affected by the timing of meal in take after resistance exercise training, This was based on the following pr evious results: 1) Nutrient intake right after exercise resulted in an incr ease in muscle mass and a decrease in abdominal fat mass as well as muscle protein synthesis when compared to the intake of a meal later after the exe rcise; and 2) body composition has been proposed to be a good predictor of bone mass. To substantiate our hypothesis, 20 male rats were assigned to ei ther a group fed a meal right after squat exercise (R) or a group fed a mea l 4 h after the exercise (L). The 10-wk training program consisted of appro ximately 70% of one repetition maximum for each animal, 15 repetitions per set, 10 sets per day, 3 d per week. As a result, hindlimb muscle mass in th e R group was greater (p < 0.05) than that in the L group and abdominal fat mass was less (p < 0.01) in the R group as compared to the L group, regard less of there being no significant difference in body weight between the gr oups. Bone volume in the tibia (p < 0.01) and femur (p < 0.05) were both si gnificantly greater in the R group than in the L group. Bone mineral conten t index (BMCI) and bone mineral density index (BMDI) in the tibia of the R group were significantly (p < 0.05) greater than the corresponding values o f the L group. The greater BMCI and BMDI in the tibia were positively and s ignificantly (p < 0.05) related with hindlimb muscle mass, but not with abd ominal fat mass. There was no significant difference in BMCI and BMDI in th e femur between the groups. These results suggest that the R regimen may co ntribute to increased bone acquisition in the tibia as compared to the L re gimen, and this effect is partly due to the enlargement of muscle mass in t he R group as compared to the L group.