Leucine Threshold In Practice

Leucine is an essential amino acid.

It is found in high concentrations of meat and dairy compared to most foods.

Increased leucine concentration in the blood triggers muscle cells to open up to adding more amino acids.

Think of this trigger like a light switch. mTor is the name of this trigger.

It's on or it's off.

Ingesting around 3g of leucine is enough to maximally trigger the leucine threshold.

There is a "dimmer" mechanism here where it can be "on a little" from around 2g of leucine ingested to 3g fully on. Over that, there is no greater signaling effect from more leucine in the blood according to muscle experts.

Older muscle (people) requires more protein to trigger muscle synthesis than young muscle which might only require 1g ingested to stimulate synthesis.

This doesn't mean that more amino acids in the blood won't have more impact. Just that the light cannot go on any brighter to signal muscles to take on new amino acids from the blood.

(Training / damaging a muscle is another way to make a muscle cell open up to new amino acids.)

Like all biological cycles, there is a rhythm. The cells will gradually synthesize less new proteins 2-4 hours after the leucine threshold has been reached. The leucine threshold can be triggered 3-4 times per day.

This means constant grazing on protein may not work well for natural muscle gain.

It's also unlikely that 1 big meal/day is going to add maximal muscle mass.

It may be great for convenience and maintenance and getting lean but it's unlikely the best option for maximal muscle gains.

Only 3g of leucine = 150-200g of meat (there is some variation between meat sources but this is a good way to remember it).

Remember this is just a SIGNAL, all the other amino acids are required in the correct concentrations to actually MANUFACTURE THE NEW TISSUE. But the SIGNAL must be there.

The better the quality of the raw materials and the better the hormonal environment

2 primary triggers to signal Muscle Protein Synthesis as we age (MPS) are:

1. Leucine

2. Strength training

Hormones and genetics are going to influence the amount and the quality of that protein.