Recovery of muscle glycogen concentrations in sled dogs during prolonged exercise

Erica McKenzie, Todd Holbrook, Kathy Williamson, Christopher Royer, Stephanie Valberg, Ken Hinchcliff, Eduard Jose-Cunilleras, Stuart Nelson, Michael Willard, Michael Davis

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Purpose: To determine the depletion of muscle glycogen during five consecutive days of endurance exercise in Alaskan sled dogs consuming a high-fat, low-carbohydrate diet. Methods: Forty-two fit Alaskan sled dogs were used in the study, of which six dogs served as nonexercising control animals. The remaining 36 dogs ran 160 km·d-1 for up to 5 d while consuming a diet providing approximately 50% of calories as fat and 15% as carbohydrate. Muscle biopsies were performed on six randomly selected dogs before feeding and within 4 h after each 160-km run was completed. Muscle samples were prepared for analysis of glycogen content and myosin ATPase staining. Serum creatine kinase (CK) activity was measured once before exercise and after each 160-km run. Results: Thirty-three of 36 dogs completed the runs. Muscle glycogen concentration was highest in sedentary dogs (340 ± 102 mmol·kg-1 dry weight), declined to 73 ± 16 after 160 km and subsequently increased to similar levels between 320 and 800 km (320 km: 177 ± 34; 800 km: 213 ± 44). Postexercise serum CK activity was significantly elevated throughout the study. Conclusion: Skeletal muscle in Alaskan sled dogs has remarkable glyconeogenic ability as demonstrated by repletion to greater than 50% of resting muscle glycogen concentrations after the second of five consecutive 160-km runs even when fed a low-carbohydrate, high-fat diet. Whether this finding is attributable to rapid repletion of muscle glycogen during brief recovery periods versus progressive utilization of alternative substrates remains to be investigated.

Original languageEnglish (US)
Pages (from-to)1307-1312
Number of pages6
JournalMedicine and science in sports and exercise
Issue number8
StatePublished - Aug 1 2005


  • Canine
  • Carbohydrate
  • Fat
  • Muscle biopsy


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