l-Arginine supplementation does not improve muscle function during recovery from resistance exercise.

The purpose of this study was to investigate the effects of l-arginine supplementation on muscle recovery after a single session of high-intensity resistance exercise (RE). Twenty healthy young adult participants (22.8 ± 3.4 years old) were assigned to 1 of 2 groups (N = 10 per group): a placebo-supplement group or an l-arginine-supplement group. The groups completed a session of high-intensity RE (0 h) and 3 subsequent fatigue test sessions (at 24, 48, and 72 h postexercise) to assess the time course of muscle recovery. During the test sessions, we assessed the following dependent variables: number of maximum repetitions, electromyographic signal (i.e., root mean square (RMS) and median frequency (MF) slope), muscle soreness, perceived exertion, blood levels of creatine kinase (CK) and lactate, and testosterone:cortisol ratio. Number of maximum repetitions increased at 48 and 72 h postexercise in both groups (time, P < 0.05). CK levels and muscle soreness increased at 24 h postexercise and then progressively returned to baseline at 72 h post exercise in both groups (time, P < 0.05). Lactate levels increased immediately postexercise but were reduced at 24 h postexercise in both groups (time, P < 0.05). Testosterone:cortisol ratio, RMS, and MF slope remained unchanged during the recovery period in both groups (time, P > 0.05). No significant (P > 0.05) group × time interaction was found for all dependent variables during the recovery period. In conclusion, our data indicate that l-arginine supplementation does not improve muscle recovery following a high-intensity RE session in young adults.

Free leucine supplementation during an 8-week resistance training program does not increase muscle mass and strength in untrained young adult subjects.

The purpose of this study was to examine the effects of free leucine supplementation on changes in skeletal muscle mass and strength during a resistance training (RT) program in previously untrained, young subjects. In a double-blind, randomized, placebo-controlled study, 20 healthy young (22 ± 2 years) participants were assigned to two groups: a placebo-supplement group (PLA, N = 10) or a leucine-supplement group (LEU, N = 10). Both groups underwent an 8-week hypertrophic RT program (2 days/week), consuming an equivalent amount of leucine (3.0 g/day in a single post-training dose) or placebo (cornstarch). Quadriceps muscle strength, cross-sectional area (CSA) of the vastus lateralis (VL), and rectus femoris (RF), as well as the habitual dietary intake were assessed before and after the 8-week intervention period. There was a similar improvement in muscle strength (Leg press, LEU: +33% vs. PLA: +37%; P > 0.05, and knee extension, LEU: +31% vs. PLA: 34%; P > 0.05) and CSA (VL, LEU: 8.9% vs. PLA: 9.6%; P > 0.05, and RF, LEU: +21.6% vs. PLA: + 16.4%; P > 0.05) in the both groups from pre- to post-training. In addition, there was no significant (P > 0.05) difference in daily dietary intake between the LEU and PLA groups before and after the intervention period. Free leucine supplementation (3.0 g/day post-training) does not increase muscle strength or CSA during RT in healthy young subjects consuming adequate dietary protein intake.

L-Arginine supplementation does not enhance blood flow and muscle performance in healthy and physically active older women.

PURPOSE: The purpose of this study was to examine the effects of acute L-arginine (L-arg) supplementation on peripheral vasodilatation and muscle performance in older women. METHODS: In a double-blind, randomized, placebo-controlled study, 20 elderly women were randomly assigned in a double-blind fashion to either an L-arg (ARG, N = 10) or placebo (PLA, N = 10) group. During the first visit, both groups underwent a Doppler ultrasound exam (to assess the femoral artery vasodilatation) at rest (baseline), and immediately before and after the isokinetic strength test (performed at 80 min after supplementation). On the second and third visits, the groups completed a battery of muscle performance tests (to assess the isometric and functional strength), initiated at the same time point (80 min after supplementation). RESULTS: The femoral artery blood flow (ARG: 443.9 ± 42.8 vs. PLA: 373.1 ± 40.8 ml/min; P > 0.05) and area (ARG: 0.45 ± 0.03 vs. PLA: 0.41 ± 0.02 cm(2); P > 0.05) were similar between the groups at basal conditions, and they remained unchanged after supplementation. Following exercise, blood flow increased ~160 % above the basal level, and there was no significant (P > 0.05) difference between the ARG and PLA groups. Additionally, there were no significant (P > 0.05) differences between the ARG and PLA groups for any strength variable (isokinetic, isometric, and functional). CONCLUSION: These results show that acute L-arg supplementation provides no ergogenic effect on blood flow and muscle performance in older women.