Table 1.

Proposed future research directions to promote understanding of how several factors of protein nutrition interact to impact the stimulation of muscle protein synthesis (MPS) at rest and during exercise recovery in young and older adults.

	Source	Dose	Timing	Pattern	Coingestion
Source	Can plant protein sources stimulate a similar response of MPS compared to animal protein sources in young and older adults? Do liquid-based forms of ingested protein stimulate a greater response of MPS compared to solid-based forms of protein foods?		What impact does protein source have on the optimal timing of protein ingestion in young adults?	What impact does protein source have on the optimal protein meal pattern for the daytime stimulation of MPS in young and older adults?
Dose	What impact does protein source have on the optimal protein dose for stimulation of MPS in young adults?	What is the maximal effective dose of protein for the stimulation of MPS in older adults? What influence does individual lean body mass have on the optimal protein dose for stimulation of MPS?			What impact does macronutrient coingestion have on the optimal protein dose for stimulation of MPS in young adults?
Timing	How does the response of MPS during exercise recovery compare between the pre-exercise ingestion of casein vs. the post-exercise ingestion of whey protein?		Does the overnight stimulation of MPS with bedtime protein feeding translate into long-term gains in skeletal muscle mass?		What impact does macronutrient coingestion have on the optimal protein timing for stimulation of MPS in young and older adults?
Pattern		What impact does protein dose have on the optimal pattern of protein feeding for the aggregate daytime stimulation of MPS?		What is the impact of protein feeding pattern, combined with exercise, on the aggregate daytime stimulation of MPS in older adults?
Coingestion		What impact does coingesting carbohydrate with a suboptimal dose of protein have on MPS in young and older adults?		Does the ingestion of protein within mixed macronutrient meals impact the optimal protein meal pattern for the daytime stimulation of MPS?	What is the impact of long chain n-3 polyunsaturated fatty acid supplementation on the response of MPS to exercise and protein feeding in young and older adults?