The influence and mechanism of L-Arginine supplements on athletic performance

As a semi-essential amino acid in the human body, L-arginine participates in key physiological processes such as the urea cycle, nitric oxide (NO) synthesis, and protein synthesis. Its supplements in the field of sports nutrition focus on improving exercise endurance, enhancing strength performance, and accelerating post-exercise recovery. The core mechanisms revolve around vascular regulation, energy metabolism optimization, and oxidative stress alleviation. However, its actual effects are significantly influenced by exercise type, supplementary dosage, and individual differences.

1. Direct Impact on Exercise Performance: "Exercise Type-Dependent" Characteristics

The effect of L-arginine supplements on exercise performance exhibits a "exercise type-dependent" feature. In endurance sports such as middle- and long-distance running and cycling, most studies have shown that reasonable supplementation can extend exhaustion time and reduce perceived fatigue during exercise. For example, when athletes supplement 6–10 g of L-arginine 1–2 hours before exercise, the accumulation rate of blood lactic acid during exercise slows down, and the maximum oxygen uptake (VO₂max) can increase by 5%–10%. This effect is more pronounced especially in populations with shorter training years and weaker baseline NO synthesis capacity.

In explosive or strength-based sports such as weightlifting and sprinting, the supplementary effect is controversial: some studies have found that it can improve muscle strength output (e.g., a 3%–5% increase in 1-repetition maximum (1RM) for bench press and squat), while others indicate no significant impact on explosive indicators (e.g., vertical jump height, sprint speed). This discrepancy may be related to exercise intensity, supplementary cycle (short-term vs. long-term supplementation), and individual metabolic efficiency of amino acids. Additionally, in high-intensity interval training (HIIT), L-arginine supplementation can help athletes maintain a higher number of high-intensity intervals by alleviating insufficient oxygen supply during exercise, reducing the decline in exercise performance caused by hypoxia.

2. Core Mechanism: Role as a Precursor for Nitric Oxide Synthesis

The core of its mechanism lies in the physiological function of L-arginine as a precursor for nitric oxide synthesis. In vascular endothelial cells, L-arginine is catalyzed by nitric oxide synthase (NOS) to produce NO. As an important vasodilator, NO can activate guanylate cyclase in smooth muscle cells, promote the synthesis of cyclic guanosine monophosphate (cGMP), and ultimately lead to vascular smooth muscle relaxation. This process can significantly increase blood flow to skeletal muscles during exercise, improve the delivery efficiency of energy substrates such as oxygen, glucose, and fatty acids, and accelerate the clearance of metabolic wastes such as lactic acid and ammonia—delaying fatigue from both the "energy supply" and "waste excretion" dimensions. For instance, in endurance sports, increased skeletal muscle blood flow can enhance oxygen delivery per unit time, reduce the proportion of anaerobic glycolysis in muscle tissue, and lower the peak blood lactic acid level, thereby extending the athlete’s exhaustive exercise time.

3. Optimization of Energy Metabolism Pathways

Beyond NO-mediated vascular regulation, L-arginine also affects exercise performance by optimizing energy metabolism pathways. On one hand, it serves as a substrate for creatine synthesis: in the body, it combines with glycine and methionine to synthesize creatine, which is the precursor of phosphocreatine (PCr) in skeletal muscles. PCr can quickly provide adenosine triphosphate (ATP) for high-intensity exercises (e.g., sprinting, weightlifting), alleviating the rate of ATP consumption. Supplementing L-arginine can increase the body’s creatine reserve, enhance the muscle’s ability to supply energy rapidly during high-intensity interval exercise, and reduce strength decline caused by insufficient energy during exercise.

On the other hand, it exerts a certain regulatory effect on fat metabolism: it can accelerate the decomposition of triglycerides in adipocytes by promoting the activity of hormone-sensitive lipase (HSL), releasing free fatty acids (FFA) into the bloodstream to serve as an energy source during exercise. This process is particularly important in long-duration endurance sports, as it reduces muscle dependence on glycogen, delays glycogen depletion, and further extends exercise endurance.

4. Promotion of Post-Exercise Recovery

In terms of post-exercise recovery, L-arginine supplementation can accelerate muscle repair by reducing oxidative stress and promoting protein synthesis. After high-intensity exercise, skeletal muscles produce a large amount of reactive oxygen species (ROS), leading to cell membrane damage, increased release of inflammatory factors (e.g., TNF-α, IL-6), and subsequent muscle soreness and functional decline. L-arginine can scavenge excess ROS by increasing the level of antioxidants such as glutathione (GSH) in the body, reducing oxidative stress damage. At the same time, it inhibits the expression of inflammatory factors, alleviating post-exercise muscle soreness (e.g., reducing the severity and duration of delayed onset muscle soreness (DOMS)).

In addition, as one of the essential amino acids for protein synthesis, L-arginine can work synergistically with branched-chain amino acids (BCAAs) such as leucine to activate the mammalian target of rapamycin (mTOR) signaling pathway—a key pathway regulating protein synthesis. Once activated, it can promote the rate of protein synthesis in muscle fibers, accelerate the repair and regeneration of damaged muscle fibers, help athletes recover muscle strength more quickly, and shorten the training interval.

5. Effect Variations and Potential Considerations

However, the application of L-arginine supplements still has effect variations and potential considerations. Regarding effect variations, an individual’s baseline NO synthesis capacity (e.g., NOS activity, baseline L-arginine level in the body) is a key influencing factor: for athletes whose diets are already rich in L-arginine (e.g., red meat, nuts, legumes) or who have high NOS activity, the additional benefits from supplements may be limited; in contrast, the supplementary effect is more likely to be apparent in populations with insufficient dietary intake or excessive L-arginine consumption due to high training intensity.

Supplementary dosage and timing also need precise control: the conventional recommended dosage is 3–10 g per day, taken in 1–2 doses (1–2 hours before exercise or within 30 minutes after exercise). A dosage that is too low may fail to reach the NO synthesis threshold, while an excessively high dosage (e.g., over 15 g per day) may cause gastrointestinal discomfort (e.g., nausea, diarrhea) or interfere with the absorption of other amino acids. Additionally, differences in exercise types should be noted—endurance sports show a more consistent response to L-arginine supplementation, while the effect on strength sports is interfered by multiple factors, requiring a decision on whether to supplement based on individual training goals.

In summary, L-arginine supplements have a relatively clear positive effect on improving endurance exercise performance through NO-mediated vasodilation, energy metabolism optimization, and post-exercise recovery promotion. However, their effects on strength sports and HIIT need to be judged based on individual circumstances. In practical application, personalized adjustments should be made according to exercise type, individual metabolic characteristics, and supplementary plans (dosage, timing), while paying attention to potential gastrointestinal reactions, to maximize their positive impact on exercise performance.