The effects of amino acid supplementation on muscular performance during resistance training overreaching

J Strength Cond Res. 2003 May;17(2):250-8. doi: 10.1519/1533-4287(2003)017<0250:teoaas>;2.


The purpose of this study was to examine the effects of amino acid supplementation on muscular strength, power, and high-intensity endurance during short-term resistance training overreaching. Seventeen resistance-trained men were randomly assigned to either an amino acid (AA) or placebo (P) group and underwent 4 weeks of total-body resistance training consisting of two 2-week phases of overreaching (phase 1: 3 x 8-12 repetitions maximum [RM], 8 exercises; phase 2: 5 x 3-5 RM, 5 exercises). Muscle strength, power, and high-intensity endurance 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 P (5.2 and 3.4 kg, respectively) but not in AA, and significant increases in 1 RM squat and bench press were observed at T3-T5 in both groups. A decrease in the ballistic bench press peak power was observed at T3 in P but not AA. The fatigue index during the 20-repetition jump squat assessment did not change in the P group at T3 and T5 (fatigue index = 18.6 and 18.3%, respectively) whereas a trend for reduction was observed in the AA group (p = 0.06) at T3 (12.8%) but not T5 (15.2%; p = 0.12). These results indicate that the initial impact of high-volume resistance training overreaching reduces muscle strength and power, and it appears that these reductions are attenuated with amino acid supplementation. In addition, an initial high-volume, moderate-intensity phase of overreaching followed by a higher intensity, moderate-volume phase appears to be very effective for enhancing muscle strength in resistance-trained men.

Publication types

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

MeSH terms

  • Adolescent
  • Adult
  • Amino Acids / administration & dosage*
  • Analysis of Variance
  • Anthropometry
  • Body Composition / physiology
  • Dietary Supplements*
  • Double-Blind Method
  • Humans
  • Male
  • Muscle Fatigue / drug effects
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / physiology
  • Physical Endurance / drug effects*
  • Physical Endurance / physiology
  • Probability
  • Reference Values
  • Treatment Outcome
  • Weight Lifting / physiology*


  • Amino Acids