The application of L-leucine in sports

Core Conclusion: L-leucine enhances athletic performance through three key effects—"rapid energy supply, reducing muscle breakdown, and accelerating post-exercise recovery"—making it suitable for high-intensity strength training, prolonged endurance exercise, and other scenarios. It is recommended to supplement sequentially as "pre-exercise priming, intra-exercise supplementation, and post-exercise repair," with a single dose of 2–5g. Better results are achieved when combined with carbohydrates or other branched-chain amino acids (BCAAs).

I. Core Mechanisms of Action During Exercise

1. Rapid Energy Supply to Delay Fatigue

L-leucine is the BCAA with the highest oxidative energy efficiency, producing approximately 32 mol of ATP per mole of complete oxidation—close to glucose’s efficiency (36–38 mol ATP/mol).During high-intensity exercise, muscle glycogen is rapidly depleted. L-leucine can be directly oxidized for energy in skeletal muscle without liver metabolism, accounting for 10%–15% of total energy supply.After 60 minutes of exercise, its oxidation rate increases 3–5 times, effectively compensating for glycogen deficiency and delaying central and muscle fatigue.

2. Muscle Protection to Reduce Breakdown

Exercise-induced stress and energy shortage activate muscle protein-degrading enzymes, leading to muscle loss. L-leucine inhibits breakdown through dual mechanisms:

Activates the mTOR signaling pathway to promote muscle protein synthesis, while suppressing the ubiquitin-proteasome system to reduce muscle protein degradation.

Serves as a preferred energy substrate, preventing muscle protein from being catabolized for energy. This muscle-protective effect is more pronounced in low-carb, fat-loss, or prolonged exercise scenarios.

3. Accelerating Post-Exercise Recovery

Muscles are in a state of micro-damage after exercise, and L-leucine targets repair:

Rapidly provides energy and raw materials for muscle repair, promotes myofiber regeneration, and shortens recovery cycles (e.g., muscle soreness duration after strength training is reduced by 20%–30%).

Improves insulin sensitivity, facilitating the transport of glucose and amino acids into muscle cells, accelerating glycogen resynthesis, and reserving energy for the next exercise session.

II. Application Schemes for Different Exercise Scenarios

1. High-Intensity Strength Training (e.g., Weightlifting, Resistance Training)

Core Needs: Enhance explosive power, protect muscle mass, and accelerate muscle repair.

Supplementation Timing & Dosage:

30 minutes before exercise: 2–3g L-leucine + 20–30g rapidly absorbed carbohydrates (e.g., glucose, maltodextrin) to prime energy and lay the foundation for muscle protection during training.

Within 1 hour after exercise: 3–5g L-leucine + 30–50g carbohydrates + 20–30g high-quality protein (e.g., whey protein) to maximize muscle synthesis and repair.

Effect: Endurance during strength training improves by 15%–20%, muscle circumference growth accelerates, and muscle soreness within 48 hours post-exercise is significantly reduced.

2. Prolonged Endurance Exercise (e.g., Long-Distance Running, Cycling, Marathon)

Core Needs: Delay glycogen depletion, maintain exercise endurance, and reduce muscle breakdown.

Supplementation Timing & Dosage:

60 minutes before exercise: 2–3g L-leucine + 50–60g complex carbohydrates (e.g., oats, whole-wheat bread) for slow energy release and stable blood sugar.

During exercise (every 60–90 minutes): 1–2g L-leucine + 30–40g carbohydrates (e.g., sports drinks, energy gels) to continuously supplement energy and inhibit muscle breakdown.

Within 30 minutes after exercise: 2–3g L-leucine + 40–50g carbohydrates + 15–20g protein to rapidly restore glycogen and muscle function.

Effect: Endurance exercise duration extends by 10%–15%, muscle weakness in the later stages of exercise is reduced, and post-race recovery cycles are shortened by 1–2 days.

3. Mixed Sports (e.g., Basketball, Football, Badminton)

Core Needs: Balance explosive power and endurance, quickly restore physical fitness, and adapt to high-intensity intervals.

Supplementation Timing & Dosage:

30 minutes before exercise: 2g L-leucine + 30g carbohydrates to rapidly activate energy metabolism.

Between exercise intervals (e.g., halftime, set breaks): 1–1.5g L-leucine + 15–20g carbohydrates to quickly replenish consumption and maintain exercise status.

After exercise: 2–3g L-leucine + 30g carbohydrates + 20g protein to repair muscles and physical fitness.

Effect: Sprint ability and interval recovery speed during exercise improve, overall athletic performance is more stable, and mistakes caused by physical fatigue are reduced.

III. Supplementation Precautions & Optimized Combinations

1. Dose Control to Avoid Excess

The maximum single dose should not exceed 5g, and the total daily dose should not exceed 10g (for a 60kg body weight).

Excessive supplementation may cause gastrointestinal discomfort (e.g., bloating, diarrhea) or interfere with the absorption and utilization of other amino acids.

2. Optimized Combinations to Enhance Efficacy

Combining with other BCAAs (L-isoleucine, L-valine) at a 2:1:1 ratio synergistically protects muscles and delays fatigue, with better results than supplementing L-leucine alone.

Pairing with carbohydrates promotes insulin secretion, accelerating the transport of L-leucine into muscle cells and improving absorption efficiency.

Avoid large simultaneous intake with high-fiber foods or caffeine to prevent absorption interference or increased physical burden.

3. Adjustments for Special Populations

Athletes in fat-loss periods: Appropriately increase the dose (3–5g post-exercise) to strengthen the synergistic effect of muscle protection and fat breakdown.

Adolescent athletes: Adjust the dose according to body weight (0.3–0.5g per 10kg body weight) to avoid excessive supplementation.

Individuals with impaired liver or kidney function: Use under professional guidance to avoid metabolic burden.

IV. Indicators to Verify Application Effects

Athletic Performance: Strength improvement (e.g., bench press weight, squat weight), endurance extension (e.g., running time, cycling distance), interval recovery speed.

Physical Indicators: Muscle circumference, body fat rate, duration of post-exercise muscle soreness, glycogen recovery rate.

Subjective Feelings: Fatigue during exercise, post-exercise recovery status, sleep quality.