Muscle protein synthesis (MPS) is often described as rocket science, but the basic concept is simpler than it sounds. Imagine your muscles as a wall, and amino acids, the building blocks of protein, are the bricks. MPS is the process of adding these bricks to the wall, making it bigger. At the same time, muscle protein breakdown (MPB) is like removing bricks from the wall. Both processes are constantly happening. Growth occurs when MPS exceeds MPB.
MPS is far more critical for muscle growth than MPB for several reasons. MPB stays within a relatively small range, influenced slightly by exercise and nutrition. However, MPS can be significantly influenced, increasing three to five times. Therefore, achieving a positive muscle protein balance almost entirely depends on MPS. Reducing MPB primarily relies on eating, and minimal insulin is sufficient for maximal inhibition.
Furthermore, entirely preventing MPB could be detrimental. Like cracks in a wall, MPB removes damaged proteins, providing a stronger foundation for growth. This is why most studies focus on MPS, as it largely determines muscle protein balance in healthy individuals and athletes.
While it’s commonly believed that resistance training aims to tear down muscle, followed by protein intake to rebuild it, this is an oversimplification. Protein consumption almost always leads to MPS exceeding MPB. Recent research highlights the importance of autophagy, a form of MPB, for removing misfolded proteins, crucial for long-term health and function.
So, what is the role of training in muscle growth? Exercise signals the body’s need for protein, increasing the utilization of amino acids from nutrition for muscle building. This effect lasts for one to two days post-workout, debunking the “anabolic window” myth.
Training involves manipulating two key factors: training itself and diet. Effective training programs should adhere to scientific guidelines. Multiple sets are superior to single sets for stimulating MPS and muscle growth. Around 10 sets per week, distributed across training sessions, is generally recommended, with the exact number depending on training frequency and experience level.
The amount of weight used isn’t as critical as achieving muscular fatigue. Studies show muscle growth can occur with various weights, even with just muscle contractions, as long as fatigue is reached. Training to failure isn’t strictly necessary; staying one or two reps shy is likely sufficient.
Rest periods of at least two minutes between sets are recommended, primarily for recovery and maintaining performance in subsequent sets. Training frequency should be at least twice per week per muscle group. Whether higher frequencies are better remains debated, as diminishing returns and the complexity of studying this factor make it difficult to determine the optimal frequency.
Training intensity, often overlooked, is crucial. Volume is only effective in the context of sufficient intensity. Progressive overload, often defined as lifting heavier weights over time, is essential for long-term muscle growth. However, it can also be achieved by increasing volume or training frequency. While some bodybuilders achieve results without explicitly focusing on progressive overload, they likely experience it indirectly.
The importance of EMG for exercise selection has been debated. While some believe higher EMG amplitude indicates greater muscle activation and thus more hypertrophy, the direct link between EMG and long-term muscle growth isn’t well-established.
Muscle protein synthesis studies are often more reliable than long-term training studies due to the slow nature of muscle growth and the statistical limitations of small sample sizes and short durations in many training studies. Measuring MPS over appropriate timeframes, matching the specific stimulus being investigated (e.g., training vs. protein intake), is critical for drawing accurate conclusions.
Combining MPS data with chronic trials strengthens the evidence for the predictive value of MPS. For example, milk protein typically elicits greater MPS spikes and long-term hypertrophy compared to soy protein. While MPS studies reveal the anabolic potential of interventions, long-term studies are needed to determine the actual muscle gains achieved.
