The effects of amino acid supplementation on hormonal responses to resistance training overreaching

Metabolism. 2006 Mar;55(3):282-91. doi: 10.1016/j.metabol.2005.08.023.


The purpose of this investigation was to examine the effects of amino acid supplementation on muscular performance and resting hormone concentrations during resistance training overreaching. Seventeen resistance-trained men were randomly assigned to either an amino acid (AA) or a placebo (P) group and underwent 4 weeks of total-body resistance training designed to induce a state of overreaching. The protocol consisted of two 2-week phases (phase 1, 3 sets of 8 exercises performed for 8-12 repetitions; phase 2, 5 sets of 5 exercises performed for 3-5 repetitions). Muscle strength and resting blood samples were determined before (T1) and at the end of each training week (T2-T5). One-repetition maximum squat and bench press decreased at T2 in the P group but not in the AA group; both groups showed similar increases in strength at T3 to T5. Significant elevations in serum creatine kinase and uric acid were observed at T2 in the P group; the elevation in creatine kinase correlated highly to reductions in 1-repetition maximum squat (r = -0.67, r(2) = 0.45). Significant elevations in serum sex hormone-binding globulin were observed during overreaching in the P group from T2 to T5; this response was abolished in the AA group. Significant reductions in total testosterone were observed in the P group at T4 compared with T1, and total testosterone values were higher for the AA group than for the P group from T2 to T4. Serum 22-kd growth hormone concentrations were elevated at T2 to T5 in P group only. No differences were observed in resting cortisol and insulinlike growth factor 1. Hemoglobin concentrations were significantly reduced at T2 to T5 in the P group. These results indicate that the initial impact of high-volume resistance training is muscle strength reduction and hormonal/biochemical alterations. It appears that amino acid supplementation is effective for attenuating muscle strength loss during initial high-volume stress, possibly by reducing muscle damage by maintaining an anabolic environment.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acids / administration & dosage*
  • Creatine Kinase / blood
  • Dietary Supplements
  • Double-Blind Method
  • Exercise Tolerance*
  • Hemoglobins / analysis
  • Hormones*
  • Human Growth Hormone / blood
  • Humans
  • Hydrocortisone / blood
  • Insulin-Like Growth Factor I / analysis
  • Male
  • Peptide Fragments / blood
  • Sex Hormone-Binding Globulin / analysis
  • Testosterone / blood
  • Uric Acid / blood


  • Amino Acids
  • Hemoglobins
  • Hormones
  • Peptide Fragments
  • Sex Hormone-Binding Globulin
  • human growth hormone 22K
  • Human Growth Hormone
  • Uric Acid
  • Testosterone
  • Insulin-Like Growth Factor I
  • Creatine Kinase
  • Hydrocortisone