Recommendations

According to Wu (2016), protein intakes ranging from 1.2 to 1.7 grams per kilogram of body weight per day are considered sufficient for maintaining a positive net protein balance, which reflects the difference between rates of protein synthesis and breakdown. During resistance training, there is typically a negative protein balance, underscoring the importance of protein intake during recovery periods to stimulate muscle protein synthesis (MPS). Maintaining a positive protein balance emerges as a critical factor for muscle hypertrophy.

The research found that adults consuming only 1 gram of protein per kilogram of body weight experienced a negative nitrogen (protein) balance after each day of resistance training, leading to increased muscle atrophy. Conversely, protein intakes falling within the range of 1.2 to 1.7 grams per kilogram of body weight resulted in a positive net protein balance. This range of protein intake is deemed ideal for most individuals to sustain sufficiently high concentrations of plasma amino acids, thereby maximizing the stimulation of MPS.

The second crucial factor is protein intake distribution. According Schoenfeld & Aragon (2018), the threshold level of protein intake per meal to maximize postabsorptive rates of MPS is approximately 20 grams. They propose a daily protein intake distribution of 0.4 grams of protein per kilogram of body weight per meal (g/kg/meal), with a minimum of four meals to ensure the minimum daily protein intake is met.

Furthermore, Schoenfeld & Aragon (2018) notes that while more skewed protein intake distributions may also be acceptable, it is imperative to ensure that each meal contains at least 20 grams of protein and that daily protein intake requirements are met. This approach aims to optimize the stimulation of MPS throughout the day, maintaining sufficiently high plasma amino acid concentrations by limiting its oxidation and ureagenesis. 

The third and final condition crucial for maximizing the stimulation of muscle protein synthesis (MPS) is ensuring sufficient leucine intake. As highlighted by Norton & Wilson (2009), leucine plays a pivotal role in independently stimulating the translocation of mTORC1, a key component of MPS signaling pathways. Norton & Wilson (2019) recommend a leucine intake of 3-4 grams per meal to effectively support MPS.

Fortunately, leucine is abundantly present in various protein sources. For example, beef and chicken breast contain approximately 2 grams of leucine per 100 grams, as indicated by Rondanelli et al. (2021). Ensuring adequate consumption of foods rich in leucine can thus contribute significantly to optimizing MPS and promoting muscle growth and repair.