Effects of dietary glycaemic response after exercise on blood concentrations of substrates used indirectly for muscle glycogenesis.
BACKGROUND
Exercise depletes muscle glycogen stores, which could subsequently impair performance. Muscle glycogen replenishment is determined by substrate availability.


OBJECTIVE
To study the effects of feeding meals of varying glycaemic responses on blood concentrations of substrates used for glycogenesis in horses with exercise-induced glycogen depletion.


METHODS
In a 3-way crossover study, 7 horses received each of 3 isocaloric diets for 72 h after undergoing glycogen-depleting exercise: 1) a high soluble-carbohydrate diet, which induced a high-glycaemic (HGI) response; 2 and 3) a low soluble-carbohydrate or a mixed soluble-carbohydrate diet (control group), which both induced a similar low-to-moderate glycaemic (LGI) response. Muscle biopsies and venous samples were collected before and up to 72 h after exercise.


RESULTS
Feeding HGI diet resulted in a higher (P<0.001) rate of muscle glycogenesis over 72 h compared to LGI diets. Plasma glycerol, triglyceride, lactate, serum NEFA and total protein concentrations, and haematocrit were significantly (P<0.001) higher after compared to before exercise. Whereas no significant overall dietary effect was observed on these metabolites over 72 h, there was a tendency for glycerol, NEFA and triglyceride concentrations to be lower for LGI compared to HGI diets over 6 h after exercise (P<0.05; 1, 6 and 4-6 h after exercise, respectively).


CONCLUSIONS
These data suggest that horses fed LGI meals after exercise had limited lipid utilisation without any significant shift of substrate utilisation toward gluconeogenesis, which could have contributed to the slower rate of muscle glycogenesis compared to horses fed HGI diets.
Lacombe
V A
VA
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210, USA.
Hinchcliff
K W
KW
Kohn
C W
CW
Reed
S M
SM
Taylor
L E
LE
D000821:Animal Feed / Q000032:analysis / Q000145:classification; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D019540:Area Under Curve; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000145:classification / Q000378:metabolism*; D038321:Glycemic Index; D006003:Glycogen / Q000096:biosynthesis*; D006736:Horses / Q000378:metabolism* / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D013997:Time Factors
D004040:Dietary Carbohydrates; D006003:Glycogen