9.1 Energy Systems and Nutrient Needs for Exercise

Exercise demands different energy systems, each tailored to specific activities. From explosive movements to endurance events, our bodies adapt to produce energy efficiently. Understanding these systems helps athletes optimize their performance through proper nutrition and training.

Nutrient needs vary based on exercise type and duration. Short bursts rely on carbs, while longer activities tap into fats. Protein supports muscle repair and growth. Tailoring macronutrient ratios and timing nutrient intake can significantly boost athletic performance and recovery.

Energy Systems in Exercise

Energy systems in exercise

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• ATP-PC (Phosphagen) System powers immediate, explosive movements utilizes creatine phosphate to regenerate ATP rapidly fuels 10-15 seconds of intense activity (sprinting, weightlifting) operates without oxygen or glucose

• Glycolytic System provides short-term energy breaks down glucose for ATP production sustains 30 seconds to 2 minutes of high-intensity activity (400m run, boxing round) relies primarily on carbohydrates as fuel

• Oxidative (Aerobic) System delivers long-term energy uses oxygen to metabolize nutrients for ATP production supports prolonged, low to moderate-intensity activities (marathon, cycling) taps into carbohydrates, fats, and proteins as fuel sources

Nutrient needs for physical activity

• Short, high-intensity activities (less than 2 minutes) require carbohydrates for quick energy burst creatine supports ATP-PC system performance (100m sprint, powerlifting)

• Moderate-intensity activities (2-60 minutes) primarily utilize carbohydrates as fuel source some fat metabolism contributes to energy production (5K run, tennis match)

• Long-duration activities (over 60 minutes) demand sustained carbohydrate energy increased reliance on fat metabolism protein prevents muscle breakdown (marathon, triathlon)

• Strength and power activities necessitate protein for muscle repair and growth carbohydrates replenish glycogen stores (weightlifting, shot put)

Macronutrient ratios for athletes

• Endurance athletes require high carbohydrate intake: 55-65% of total calories moderate protein intake: 15-20% of total calories lower fat intake: 20-30% of total calories (marathon runners, cyclists)

• Strength and power athletes need moderate to high carbohydrate intake: 45-55% of total calories higher protein intake: 20-25% of total calories moderate fat intake: 25-35% of total calories (weightlifters, sprinters)

• Team sport athletes benefit from balanced macronutrient ratio carbohydrates: 45-55% of total calories protein: 15-20% of total calories fat: 25-35% of total calories (soccer players, basketball players)

• Weight-class sports athletes require individualized macronutrient ratios based on weight management goals higher protein intake maintains muscle mass during weight cuts (wrestlers, boxers)

Timing of nutrient intake

• Pre-exercise nutrition consume meal 2-3 hours before exercise focus on easily digestible carbohydrates for energy (pasta, rice) moderate protein intake supports muscle function avoid high-fat foods that slow digestion

• During exercise nutrition for activities lasting over 60-90 minutes consume easily digestible carbohydrates maintain blood glucose levels (energy gels, sports drinks) hydrate with water or sports drinks replace lost fluids and electrolytes

• Post-exercise nutrition consume meal or snack within 30-60 minutes after exercise emphasize carbohydrates to replenish glycogen stores include protein to support muscle recovery and growth (chocolate milk, turkey sandwich) rehydrate with water or electrolyte-rich beverages

• Nutrient timing strategies include carbohydrate loading for endurance events protein timing for muscle protein synthesis strategic use of caffeine for performance enhancement (pre-workout supplements, coffee)