Abstract
The aim of this study was to test the effects of two disparate isonitrogenous, isocaloric pre-exercise feeds on deuterium-oxide (D2O) derived measures of myofibrillar protein synthesis (myoPS) in humans. Methods: In a double-blind parallel group design, 22 resistance-trained men aged 18 to 35 years ingested a meal (6 kcal·kg−1, 0.8 g·kg−1 carbohydrate, 0.2 g·kg−1 fat) with 0.33 g·kg−1 nonessential amino acids blend (NEAA) or whey protein (WHEY), prior to resistance exercise (70% 1RM back-squats, 10 reps per set to failure, 25% duty cycle). Biopsies of M. vastus lateralis were obtained pre-ingestion (PRE) and +3 h post-exercise (POST). The myofibrillar fractional synthetic rate (myoFSR) was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography–pyrolysis–isotope ratio mass spectrometry (GC-Pyr-IRMS). Data are a mean percentage change (95% CI). Results: There was no discernable change in myoFSR following NEAA (10(−5, 25) %, p = 0.235), whereas an increase in myoFSR was observed after WHEY (28 (13, 43) %, p = 0.003). Conclusions: Measured by a D2O tracer technique, a disparate myoPS response was observed between NEAA and WHEY. Pre-exercise ingestion of whey protein increased post-exercise myoPS, whereas a NEAA blend did not, supporting the use of NEAA as a viable isonitrogenous negative control.
Highlights
Resistance exercise increases uptake of amino acids into the muscle and stimulates muscle protein synthesis (MPS) [1]
The aim of the present study was to investigate whether the nonessential amino acids (NEAA) blend could act as a viable isonitrogenous negative control, in human feeding studies assessing MPS after resistance-exercise
No differences were observed between NEAA and whey protein (WHEY) groups for age, stature, body mass, 1 body mass one-repetition maximum (1RM) strength, resistance training experience, or resistance training performance (Table 2)
Summary
Resistance exercise increases uptake of amino acids into the muscle and stimulates muscle protein synthesis (MPS) [1]. Consumption of EAA-rich protein in temporal proximity to resistance exercise further stimulates MPS in a dose-dependent manner [5], whereas nonessential amino acids (NEAA) do not have any additional stimulatory effect on MPS when co-ingested with EAA [6,7]. To assess the effect of dietary protein feeding on MPS in a nitrogen-balanced design, an isonitrogenous control is required [8,9]. The aim of the present study was to investigate whether the NEAA blend could act as a viable isonitrogenous negative control, in human feeding studies assessing MPS after resistance-exercise
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