Effect of intermittent blood volume fluctuation of light resistance exercise after ingestion of high-protein snacks on plasma branched-chain amino acid concentrations in young adults
Journal Title (Medline/Pubmed accepted abbreviation): J Nutr Sci Vitaminol
Year: 2010
Volume: 56
Number: 4
Page numbers: 255-259
doi: 10.3177/jnsv.56.255

Summary of Background and Research Design

Background:High-protein snacks ingested 3 hours after a meal elevate the blood concentration of branched-chain amino acids (BCAAs). Muscle uptake and utilization of amino acids may contribute to increases in both mass and strength. However, resistance exercise produces reduced blood flow to various muscles followed by an increased blood volume to the muscles between exercise sets. Therefore, blood volume fluctuation may control the efficacy of amino acid uptake by the muscles.

Hypothesis/purpose of study:To investigate the effects of different blood volume fluctuation times on the efficiency of amino acid utilization and BCAA and glucose plasma concentrations.

Subjects:8 healthy adults (3 men and 5 women) participated in this study (age, 24.5 ± 4.6 yr; height, 168.1 ± 7.6 cm; weight, 58.7 ± 7.6 kg; body mass index, 20.7 ± 1.2 kg/m2).

Experimental design: Randomized, cross-over study

Treatments and protocol:Participants were randomized to either a high number of exercise repetitions with long intervals (HL) or a low number of repetitions with a short interval (LS). Each group crossed over to the other type of exercise following a 7-day interval. A standardized meal was provided 3 hours before the high-protein snack (dried egg white [51 kcal/14.5 g], gelatin [2.5 g], sugar [18 g], and water; total of 15 g protein and 130 kcal). The resistance exercise started 1 hour after snack ingestion and consisted of 135 total slow arm flex/extensions over 15 minutes (HL, 9 sets of 15 repetitions with 10-sec rest intervals; LS, 27 sets of 5 repetitions with 3- to 4-sec rest intervals). Blood samples for BCAA and glucose concentrations were collected before snack ingestion and at 60 and 90 minutes after snack ingestion. Blood volume to the antebrachial muscle, as reflected by total hemoglobin content of the muscle measured via infrared spectroscopy, was determined during the total exercise time.

Summary of research findings:
  • Plasma BCAA concentrations were significantly higher following snack ingestion at both 60 and 90 minutes in both exercise groups.
    • In the HL group, BCAA concentrations continued to increase from 60 to 90 minutes.
    • In the LS group, BCAA concentrations stopped increasing during the exercise resulting in a significant difference between the 2 groups between 60 and 90 minutes (P < .05).
  • Plasma glucose concentrations decreased after snack ingestion at 60 minutes then increased at 90 minutes in both exercise groups without significant differences.
  • Blood volume changes were similar in both exercise groups (decreased during arm flex/extend and increased during rest intervals).
    • Periodic fluctuation (transition from rest interval to exercise) was similar between the exercise groups.

Interpretation of findings/Key practice applications:

The results of this study suggest that the pattern of blood volume fluctuations can influence the efficiency of amino acid uptake in muscles during resistance exercise. The higher frequency that blood volume returned to normal (typically 3 to 4 sec) in the LS group may have allowed increased amino acid uptake compared with the HL group. This was evidenced by the lack of increase in BCAA plasma concentration after the exercise sets in the LS group from the 60- to 90?minute time points. However, actual amino acid uptake by the muscle tissue was not measured to confirm utilization of the BCAA. It is not clear whether the lack of increase in plasma BCAA (and glucose as well) observed at the 90-minute time point for the LS group vs the HL group actually represented increased muscle uptake of these nutrients.
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