Ingestion of starch-rich meals after exercise increases glucose kinetics but fails to enhance muscle glycogen replenishment in horses.
Authors: Jose-Cunilleras Eduard, Hinchcliff Kenneth W, Lacombe Veronique A, Sams Richard A, Kohn Catherine W, Taylor Lynn E, Devor Steven T
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary After intense exercise depletes muscle glycogen stores and compromises subsequent performance, nutritionists and coaches often recommend feeding starch-rich concentrates immediately post-exercise to facilitate rapid glycogen resynthesis. However, this 2006 study by Cunilleras and colleagues challenges the efficacy of this common practice by demonstrating that whilst starch meals dramatically elevate blood glucose and insulin levels, they fail to meaningfully enhance muscle glycogen recovery in horses. Seven horses were studied across three feeding regimes following exercise-induced glycogen depletion: complete feed withholding for 8 hours, half-rations of hay, or corn concentrate fed at 15 minutes and 4 hours post-exercise; starch ingestion produced threefold greater whole-body glucose turnover and substantially elevated blood glucose (5.7 versus 4.7 mM) and insulin (79.9 versus 39.0 pM) compared to fasting, yet muscle glycogen concentrations immediately post-exercise and at 24 hours showed negligible differences between treatments. The findings suggest that factors beyond glucose availability—potentially insulin sensitivity in fatigued muscle, substrate partitioning, or the rate of glycogen synthase activation—may fundamentally limit post-exercise glycogen replenishment in horses, implying that feeding strategy alone cannot overcome these physiological constraints and that recovery protocols may need to address other mechanisms to optimise glycogen restoration between training sessions.
Read the full abstract on PubMed
Practical Takeaways
- •Feeding starch-rich concentrates immediately after exercise does not meaningfully improve muscle glycogen recovery in horses, despite high blood glucose and insulin levels
- •Post-exercise feeding strategy should not rely on starch meals alone for glycogen replenishment; alternative nutritional or training approaches may be needed to restore muscle glycogen after fatiguing work
- •Hay-based feeding provides similar glycogen recovery outcomes to starch feeding without the metabolic stress of hyperglycemia and hyperinsulinemia
Key Findings
- •Starch-rich meals after exercise increased blood glucose (5.7 vs 4.7 mM) and insulin (79.9 vs 39.0 pM) compared to feed withholding
- •Whole body glucose kinetics increased 3-fold with starch feeding (15.5 vs 5.3 μmol kg⁻¹ min⁻¹) compared to fasting
- •Despite marked increases in glucose availability, muscle glycogen replenishment was minimal and not significantly different between starch-fed and fasted horses at 0 h (171 vs 170 mmol/kg) and 24 h (260 vs 294 mmol/kg)