The role of L-Arginine in muscle growth and repair

As a semi-essential amino acid in the human body (it can be synthesized by the body under normal physiological conditions, but requires exogenous supplementation in special scenarios such as high-intensity exercise and wound repair), L-arginine does not directly "build muscle" in muscle growth and repair. Instead, it supports muscle tissue synthesis and injury recovery from multiple dimensions by regulating physiological metabolic pathways and optimizing the microenvironment. The specific mechanisms can be analyzed as follows:

First, L-arginine is a key precursor for nitric oxide (NO) synthesis in the body—under the catalysis of nitric oxide synthase (NOS), it can be converted into NO and citrulline. As an important vasodilator, NO can significantly dilate the microvessels around muscle tissue and increase local blood flow. This process directly brings two benefits: on one hand, more blood carrying oxygen, glucose, and amino acids (such as leucine, the core raw material for muscle synthesis) flows into muscle cells, providing sufficient "energy and raw material supply" for muscle synthesis; on the other hand, increased blood flow accelerates the clearance of metabolic waste (such as lactic acid and ammonia produced during exercise), reducing the damage of waste accumulation to muscle cells and creating a better microenvironment for muscle growth. Especially after high-intensity training, this "microcirculation improvement" effect can indirectly enhance the efficiency of muscle synthesis.

Second, the regulation of protein metabolism by L-arginine is the core link in its support for muscle growth. It can affect protein balance through two pathways:

As an amino acid raw material, it directly participates in muscle protein synthesis. Although it is not an essential amino acid, when the muscle synthesis substrate (amino acid pool) is insufficient (e.g., increased muscle breakdown after exercise or insufficient dietary protein intake), exogenous supplementation of L-arginine can replenish the amino acid pool and alleviate the "substrate deficiency" problem of muscle protein.

It inhibits muscle protein breakdown by regulating related signaling pathways. Studies have shown that L-arginine can reduce the activity of the "ubiquitin-proteasome system" (the core system responsible for protein degradation) in muscle tissue, and at the same time reduce the catabolic effect of pro-catabolic factors (such as cortisol) on muscles. This breaks the imbalance of "breakdown > synthesis", promotes an increase in net muscle protein synthesis, and lays the foundation for muscle hypertrophy.

In terms of muscle repair, the role of L-arginine focuses on "accelerating injury repair" and "alleviating inflammatory responses". High-intensity exercise (such as resistance training) causes micro-tears in muscle fibers, accompanied by local inflammatory responses (such as leukocyte infiltration)—moderate inflammation is a starting signal for repair, but excessive inflammation will prolong the repair cycle and even exacerbate muscle damage. By promoting NO synthesis, L-arginine can regulate the activity of immune cells (such as macrophages), inhibit the release of excessive inflammatory factors (such as tumor necrosis factor-α, interleukin-6), and promote the expression of anti-inflammatory factors (such as interleukin-10). This "balances the inflammatory response" and creates a mild environment for muscle fiber repair. In addition, L-arginine can also participate in collagen synthesis (collagen is an important component of muscle connective tissue), helping to repair connective tissue damage between muscle fibers, enhance the stability of muscle structure, and reduce the duration of delayed onset muscle soreness (DOMS) after exercise.

It should be noted that the effect of L-arginine is "dose-dependent" and "individual-specific":

For healthy adults, daily diet (such as red meat, fish, nuts, and legumes) can already meet basic needs. The effect of additional supplementation is more obvious in populations with "insufficient dietary protein intake" or "high-intensity training".

Excessive supplementation (e.g., more than 10-15g per day) may cause gastrointestinal discomfort (such as nausea and diarrhea) or affect blood glucose (diabetic patients need to be cautious).

At the same time, its effect must be combined with "sufficient protein intake", "scientific resistance training", and "adequate rest"—relying solely on L-arginine cannot achieve effective muscle growth. Instead, it acts more as an "auxiliary factor" to optimize the overall process of muscle synthesis and repair.