FUELS & MEALS Flashcards
(6 cards)
Understand how eating BEFORE exercise impacts the
contribution of different fuels during a subsequent endurance exercise session (i.e., what happens and HOW it happens)
Increases carbohydrate (CHO) utilization: Ingesting CHO before endurance exercise raises blood glucose and insulin levels, promoting CHO oxidation and suppressing fat oxidation.
Muscle glycogen sparing: Early reliance on blood glucose preserves muscle glycogen for later stages.
Risk of transient hypoglycemia: A high-GI meal can trigger a rapid insulin spike, leading to a temporary drop in blood glucose (~30 min post-ingestion).
Define transient hypoglycemia and how it happens.
A temporary drop in blood glucose (~30-60 mg/dL) occurring 30-45 min after eating high-GI CHO before exercise.
Caused by:
- High insulin levels (from pre-exercise CHO intake).
- Exercise-induced glucose uptake (muscles rapidly absorb glucose).
Symptoms: Fatigue, dizziness, weakness (often resolves as gluconeogenesis & lipolysis compensate).
Define the Glycemic index.
A measure of how fast a carbohydrate raises blood glucose levels.
High GI (>70): Rapid glucose spike (e.g., white bread, glucose).
Moderate GI (56-69): Moderate response (e.g., brown rice).
Low GI (<55): Slow glucose release (e.g., oats, legumes).
Understand how eating DURING exercise impacts fuel
metabolism and endurance exercise performance (i.e., what happens and HOW it happens)
Maintains blood glucose levels → Delays glycogen depletion.
Spares liver glycogen → Reduces fatigue.
Enhances endurance → Sustains CHO oxidation, delaying fatigue.
How? CHO intake provides immediate glucose for oxidation, preventing reliance on muscle glycogen.
Recommendation: 30-60g CHO/hour for events lasting >60-90 min.
Effects and benefits of eating carbohydrate AFTER prolonged endurance exercise
Replenishes muscle glycogen (critical for recovery).
High insulin response enhances glucose uptake (via GLUT4 activation).
Optimal window: First 30-60 min post-exercise (fastest glycogen resynthesis).
Recommended intake: 1.0-1.2 g CHO/kg/hr for rapid recovery.
Describe the impact of chronic aerobic training on fuel
metabolism / utilization.
Increased fat oxidation → Enhanced use of fat at submax intensities, sparing glycogen.
Greater mitochondrial density → More efficient ATP production from fat and CHO.
Higher glycogen storage → Delays fatigue by prolonging CHO availability.
Increased capillary density & enzyme activity → Improved oxygen and nutrient delivery.
