Hormonal
Resistance and nonresistance exercise suppress muscle protein synthesis (MPS) during the activity itself, but both types stimulate MPS significantly in the postexercise period, creating a window for muscle growth when combined with nutrient intake.
Your muscles are not building protein while you are lifting weights; in fact, synthesis drops during the activity to prioritize energy for movement. The actual building process (MPS) ramps up significantly *after* you finish exercising. To capitalize on this post-exercise window, you must consume protein (amino acids) to shift your body from a negative to a positive protein balance.
Exercise of both the resistance and nonresistance types appears to depress muscle protein synthesis (MPS), whereas muscle protein breakdown (MPB) probably remains unchanged during exercise. However, both MPS and MPB are elevated after exercise in the fasted state... Positive net balance is achieved only when amino acid availability is increased, thereby raising MPS markedly.
Why this rating
Based on a comprehensive review of stable isotope tracer studies in humans, though some methodological contradictions exist.
Source
Human muscle protein synthesis and breakdown during and after exercise
Vinod Kumar et al. · Journal of Applied Physiology · 2009
DOI 10.1152/japplphysiol.91481.2008
More from this paper
- Post-exercise amino acid availability is less effective than insulin at inhibiting muscle protein breakdown (MPB); insulin secretion is primarily stimulated by glucose availability.Good
- Resistance exercise intensity affects myofibrillar protein synthesis (MPS) in a dose-dependent manner at low intensities, plateauing between 60-90% of 1RM, while training status alters the specific protein fractions synthesized (myofibrillar vs. mitochondrial).Good
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