Minimal dose of milk protein concentrate to enhance the anabolic signalling response to a single bout of resistance exercise; a randomised controlled trial

Resistance training is a potent stimulus to induce muscle hypertrophy. Supplemental protein intake is known to enhance gains in muscle mass through activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway, which initiates protein translation. While the optimal dose of high quality protein to promote post exercise anabolism in young or older men has been investigated, little is known about the minimum doses of protein required to potentiate the resistance exercise activation of anabolic signalling in middle aged men. Twenty healthy men (46.3 ± 5.7 years, BMI: 23.9 ± 6.6 kg/m ) completed a single bout of unilateral resistance exercise consisting of 4 sets of leg extension and press at 80% of 1 repetition maximum. Participants were randomised to consume either formulated milk product containing 9 g milk protein (FMP) or an isoenergetic carbohydrate placebo (CHO) immediately post exercise, in a double blind fashion. A single muscle biopsy was collected at pre-exercise baseline and then bilateral biopsies were collected 90 and 240 min after beverage consumption. P70S6K phosphorylation was increased with exercise irrespective of group, P70S6K was increased with exercise only in the FMP group at 240 min. Likewise, rpS6 phosphorylation was increased with exercise irrespective of group, rpS6 increased to a greater extent following exercise in the FMP group. mRNA expression of the amino acid transporter, LAT1/ increased with both exercise and beverage consumption irrespective of group. PAT1/ , CAT1/ and SNAT2/ mRNA increased only after exercise regardless of group. Nine grams of milk protein is sufficient to augment some measures of downstream mTORC1 signalling after resistance exercise but does not potentiate exercise induced increases in amino acid transporter expression. Formulated products containing nine grams of milk protein would be expected stimulate muscle anabolism after resistance exercise. New Zealand Clinical Trials Registry ACTRN12615001375549. Registered: 17 December, 2015.