Effect of acute absolute and relative supplementation of L-arginine on a 1 km and 16.1 km time trial performance in trained cyclists

Abstract

Background - The effects of oral L-arginine (ARG) supplementation on exercise parameters have previously been investigated. However, there is a lack of research to date examining ARG supplementation without additional compounds or on the effects of absolute versus relative dosing.
Purpose - The purpose of the present study was to investigate the effects of acute absolute (6g) and relative (0.15 g·kg-1 of body mass) ARG supplementation for 2 days on aerobic and anaerobic performance in trained cyclists.
Methods - The experimental protocol was a single blind, crossover design and was approved by the University of Central Lancashire Ethical Committee. Eight male trained cyclists were required to perform a 1 km and 16.1 km cycling time trials (TT) on three separate occasions, those being baseline without supplementation (BL), with absolute ARG (ABS) and relative ARG (REL) supplementation. Prior to testing, participants were required to complete a 5-minute self-paced warm up on an SRM cycle ergometer. The testing protocol required each participant to complete the 1 km and 16.1 km TT’s separated by a 15 minute passive recovery period. During testing, participants received no temporal, verbal, or physiological feedback, and were only aware of the distance they had covered. The protocol used a 7 day washout period between the 3 trial conditions. Time to completion and mean power output (Wmean) were determined for each trial. Participants maintained their habitual diet throughout the study and were instructed to avoid alcohol and caffeine, and strenuous activity for 24-48 hours preceding each test session. On the 2 days of supplementation, participants were required to consume the ARG supplement with 500 ml water, 90 minutes before testing commenced, in accordance with the recommendations of previous research (Bode-Böger et al., 1998; Bailey et al., 2010a; Forbes and Bell, 2011). A repeated measure ANOVA was used to determine any significant main effects between conditions, whilst Bonferroni pairwise comparisons were used to determine where differences lay. Effect size (ES) was calculated using partial eta2.
Results – A significant main effect was only found for Wmean during 16.1 km TT (P = .002; ES = .59), with significant differences between BL and REL conditions (P = .01). Mean power output during the 16.1 km TT’s were BL 196.19 ± 32.40, ABS 206.31 ± 38.10 and REL 215.81 ± 31.56 W respectively. Mean power output during the 1 km TT’s were BL 358.14 ± 94.73, ABS 415.51 ± 65.36 and REL 426.35 ± 70.86 W (main effect was P = .057; ES = .40). No significant differences were revealed for time to completion for either 1 km TT (mean time = BL 1.29 ± 0.08, ABS 1.23 ± 0.05 and REL 1.22 ± 0.04 min respectively; main effect was P = .061; ES = .40) or 16.1 km TT (mean time = BL 27.27 ± 1.50, ABS 27.02 ± 1.58 and REL 26.52 ± 1.34 min respectively; main effect was P = .140; ES = .25).
Discussion – With the exception of 16.1 km mean power output, the present study found no significant improvements in TT performance resulting from ARG supplementation. However, results demonstrated a general trend for greater improvements with supplementation and particularly for REL dosing. The moderate effect sizes reported may indicate that the lack of significance may be attributed to the small sample size used. The levels of improvement shown are comparable to those shown in previous ARG supplementation studies (Schaefer et al., 2002; Camic et al., 2010; Bailey et al., 2010a; Campbell et al., 2006; Koppo et al., 2009). Although the minimum dose of ARG supplementation required to improve performance remains unknown, based on the results of the present an acute 6g dose of ARG 90 minutes prior to athletic performance is recommended to elicit performance improvements. Furthermore, the present study also demonstrated greater improvements in performance following a REL dose compared to an ABS dose. Therefore, 0.15 g·kg–1 of body mass is recommended as a safer and more effective method of ARG supplementation.
Conclusion - These results suggest that acute ARG supplementation with no additional compounds can improve cycling performance. However, a larger sample size may be needed to demonstrate levels of significance.