Muscle and Liver Carbohydrates: Response to Military Task Performance by Women & Men

摘要

During the third year we have focused on making significant progress in both the MRI and the MRS portions of this project. We have been hampered by difficulty in recruiting suitable subjects and by difficulty in getting female subjects to return for a second MRS study. Nevertheless we have confirmed that (1) Women recruit their upper bodies more than men, and (2) Quadriceps glycogen is nominally depleted by our protocol in both genders. We are now able to consider several additional preliminary conclusions. (1) As prolonged exercise continues muscle recruitment patterns do not change. (2) The left biceps muscle is more heavily recruited in women (MRI) and this results in faster glycogen depletion rates (MRS) in women than in men. (3) Net liver glycogen depletion rates during exercise are slower in women in the luteal phase of their menstrual cycle than in men or in women in the follicular phase. This suggests that hormonal fluxes exert an effect under our experimental conditions. We have begun a second MRS study on the effect of four consecutive days of our protocol and early data suggest that in both genders exercised muscles progressively supercompensate glycogen. The major failure of this current project is the paucity of suitable subjects that has resulted in our low numbers of completed studies to date. We are considering increasing subject compensation, and we intend to continue the project beyond term in order to confirm or refute our conclusions thus far.