Journal Title (Medline/Pubmed accepted abbreviation): J Nutr Sci Vitaminol
Page number: 233-238
doi (if applicable):
Summary of background and research design:
Background: Preclinical data suggest that both light resistance exercise and ingestion of a high-protein snack (HPS) after a basal meal are necessary to prevent sarcopenia. Clinical evidence showed that this combination promoted branched-chain amino acid (BCAA) use in peripheral tissues, which could possibly increase muscle mass and strength.
Hypothesis/Purpose:The purpose of this study was to evaluate the effectiveness of HPS ingestion after a basal meal followed by dumbbell exercises on increasing muscle mass and strength.
Subjects: Ten adult males participated in this study (mean age, 24.5 ± 1.2 yr; height, 172.5 ± 2.0 cm; weight, 64.4 ± 2.1 kg; body mass index, 21.6 ± 0.6 kg/m2).
Experimental design: Cross-over
Treatments Protocol: Each participant followed 3 different 5-week test conditions separated by a recovery interval to reset training effects: snack-exercise (SE; HPS 3 hr after breakfast every day and dumbbell exercises for 30 to 60 min 5 times/wk), snack-sedentary (SS; HPS 3 hr after breakfast every day and no exercise), and no snack-exercise (NE; ½ HPS with breakfast and lunch and exercise as SE). The HPS consisted of dried egg whites, sugar, and water (13 g protein and 120 kcal). Food diaries were kept during the first and fifth weeks of each test condition; diet was not controlled. Body composition, muscle cross-sectional area (forearm flexor and vastus lateralis [thigh]), and muscle strength (grip and knee extensor muscle) were assessed before and after each test condition
Summary of research findings:
- Dietary intake during each of the test conditions was not significantly different from before the test conditions.
- Lean body mass increased (2.1%) and fat mass decreased (–5.6%) from baseline only in the SE condition (P ≤ .05 for both).
- No change was observed in body weight for all conditions.
- Cross-sectional muscle area of the forearm was increased 2.8% from baseline in the SE group (P < .01).
- No significant changes from baseline were observed in the forearms of the other 2 groups.
- There were no significant changes from baseline in the vastus lateralis for any group.
- Isometric right knee extensor strength increased 8.2% from baseline in the SE group (P < .01) and was significantly higher compared with the SS and NE groups (P < .05 for both).
- There was no significant change from baseline in isokinetic right knee extensor strength in any group.
- Grip strength of the right hand was increased from baseline in both the SE and NE groups (P ≤ .05 for both), each of which was higher than grip strength in the SS group (P < .01 for both).
Interpretation of findings/Key practice applications:
In this study, continued intake of HPS after a meal together with resistance exercise increased muscle mass and strength. It is estimated that amino acids in blood are highest 30 to 60 minutes following ingestion, which allows for optimal promotion of protein synthesis. Although the NE group ingested the same total HPS per day, timing of intake was with the meal and the interval before exercise was longer. In addition, the dumbbell exercise causes intermittent changes in blood flow volume in muscle tissues, which may promote uptake of amino acids. However, optimal blood flow fluctuations for amino acid uptake by skeletal muscles will need to be established.