Leucine Threshold and Muscle Protein Synthesis

LatinoBulk · Post by **LatinoBulk** » Thu Jan 22, 2026 2:30 am

Is the 3g leucine threshold still the gold standard for triggering MPS in older athletes?

AndeanLifter · Post by **AndeanLifter** » Thu Jan 22, 2026 3:05 am

Recent data suggests 4g might be necessary for those over 50 due to anabolic resistance.

TropicStrength · Post by **TropicStrength** » Thu Jan 22, 2026 3:45 am

The mTOR pathway sensitivity definitely declines with age. Dosage timing matters more now.

CaliFlex · Post by **CaliFlex** » Thu Jan 22, 2026 4:32 am

Does the source matter? Whey vs Soy in terms of leucine kinetics?

MedellinMuscle · Post by **MedellinMuscle** » Thu Jan 22, 2026 5:15 am

Whey is always superior for the leucine spike. Soy just doesn't hit the same peak concentration.

LatinoBulk · Post by **LatinoBulk** » Thu Jan 22, 2026 5:50 am

But if you equate for leucine content, does the total protein source still matter?

AndeanLifter · Post by **AndeanLifter** » Thu Jan 22, 2026 6:25 am

Trommelen's work suggests that as long as leucine is equated, MPS rates are similar.

TropicStrength · Post by **TropicStrength** » Thu Jan 22, 2026 7:10 am

What about the other EAAs? You can't just trigger with leucine and expect magic without the building blocks.

CaliFlex · Post by **CaliFlex** » Thu Jan 22, 2026 7:40 am

Correct. Leucine is the spark, but the EAAs are the fuel.

MedellinMuscle · Post by **MedellinMuscle** » Thu Jan 22, 2026 8:15 am

I think a lot of people miss the "refractory period" of MPS. You can't just keep spiking it.