EFFECT OF DIET AND TRAINING ON MUSCLE GLYCOGEN-STORAGE AND UTILIZATION IN SLED DOGS

Two groups of eight Alaskan huskies fed either a high-fat (HFD; 60% kc al from fat and 15% kcal from carbohydrate) or a high-carbohydrate die t (HCD; 60% kcal from carbohydrate and 15% kcal from fat) performed st andard aerobic (1 h at 4 m/s on a 0% slope) and anaerobic (3 min at 6. 7 m/s on a 10% slope) tests before and after training. Before and imme diately after each exercise test, venous blood samples were collected and analyzed for lactate and pyruvate, and muscle biopsies were obtain ed under local anesthesia from the semitendinosus muscle and analyzed for total muscle glycogen (TMG) concentration. Training was associated with a significant increase in preexercise TMG in both diet groups; t his effect was most marked in the HCD. There was no effect of diet or training on TMG utilization during the aerobic tests. The rate of TMG utilization during the anaerobic tests was between 20 and 40 times gre ater than that measured during the aerobic tests. The pre- to postexer cise change in TMG was dependent on preexercise TMG in the HCD and HFD for both anaerobic tests (HCD: P < 0.01, r = 0.81; HFD: P less than o r equal to 0.03, r = 0.66). It is concluded that the increased glycoge n storage associated with the HCD was more than offset by the more rap id rate of glycogen utilization in this group. HFD facilitated carbohy drate sparing during intense exercise and should thus be a better diet ary strategy for endurance in sled dogs.