Physical training causes adaptations in the metabolism of muscles, one of which is a switch in the energy sources utilized. To study the switch in energy metabolism as a result of exercise, Hood and...

Physical training causes adaptations in the metabolism of muscles, one of which is a switch in the energy sources utilized. To study the switch in energy metabolism as a result of exercise, Hood and Terjung* measured the contribution of the branched-chain amino acid, leucine, to muscle energy utilization in skeletal muscle bundles isolated from two groups of rats: one physically trained and one not trained. They measured the contribution of leucine to the total energy consumption of the muscle (percentage of total energy used) with the muscle at rest, and then during two frequencies of stimulation (15/min and 45/min) to simulate two levels of acute exercise (the data are in Table D-29, Appendix D). Analyze the data using ML or REML. Describe how you chose the covariance structure you used. Is there evidence to support the hypothesis that the percentage contribution of leucine to energy needs during exercise in trained muscle is lower than the percentage contribution in untrained (control) muscle? (If you read the section on traditional OLS ANOVA, repeat the analysis and compare the results with the ML/REML analysis.)

Table D-29