GLOSSARY

Muscle Protein Synthesis (MPS) is new protein construction within muscle. The protein fraction and measurement conditions matter; an MPS increase is not exclusively added contractile mass.

Muscle protein synthesis can involve contractile, mitochondrial or other proteins. Resistance and endurance exercise do not produce identical adaptations. More muscle synthesis therefore does not exclusively mean a visibly larger muscle. The measured protein fraction and training purpose must be specified before interpreting the result or comparing two nutrition studies.

New protein synthesis requires the necessary amino acid mixture, not only activation of a cellular signal. Leucine participates in signalling but cannot replace missing essential substrates. BCAAs supply only part of that set and should not automatically be equated with sufficient food protein or a complete essential-amino-acid supplement.

Leucine contributes a nutritional signal to protein-synthesis pathways, but the response is not one universal switch. Around 2–3 grams appears in some sport discussions, not as a fixed guaranteed threshold. Age, protein source, the amino acid mixture and exercise can all change the relationship between dose and response.