Arginine and antioxidant supplement on performance in elderly male cyclists: a randomized controlled trial

Journal of the International Society of Sports Nutrition (Impact Factor: 1.83). 01/2010; 7(1):1-7. DOI: 10.1186/1550-2783-7-13
Source: PubMed

ABSTRACT BackgroundHuman exercise capacity declines with advancing age. These changes often result in loss of physical fitness and more rapid
senescence. Nitric oxide (NO) has been implicated in improvement of exercise capacity through vascular smooth muscle relaxation
in both coronary and skeletal muscle arteries, as well as via independent mechanisms. Antioxidants may prevent nitric oxide
inactivation by oxygen free radicals. The purpose of this study was to investigate the effects of an L-arginine and antioxidant
supplement on exercise performance in elderly male cyclists.

MethodsThis was a two-arm prospectively randomized double-blinded and placebo-controlled trial. Sixteen male cyclists were randomized
to receive either a proprietary supplement (Niteworks®, Herbalife International Inc., Century City, CA) or a placebo powder. Exercise parameters were assessed by maximal incremental
exercise testing performed on a stationary cycle ergometer using breath-by-breath analysis at baseline, week one and week

ResultsThere was no difference between baseline exercise parameters. In the supplemented group, anaerobic threshold increased by
16.7% (2.38 ± 0.18 L/min, p < 0.01) at week 1, and the effect was sustained by week 3 with a 14.2% (2.33 ± 0.44 L/min, p <
0.01). In the control group, there was no change in anaerobic threshold at weeks 1 and 3 compared to baseline (1.88 ± 0.20
L/min at week 1, and 1.86 ± 0.21 L/min at week 3). The anaerobic threshold for the supplement groups was significantly higher
than that of placebo group at week 1 and week 3. There were no significant changes noted in VO2 max between control and intervention groups at either week 1 or week 3 by comparison to baseline.

ConclusionAn arginine and antioxidant-containing supplement increased the anaerobic threshold at both week one and week three in elderly
cyclists. No effect on VO2 max was observed. This study indicated a potential role of L-arginine and antioxidant supplementation in improving exercise
performance in elderly.

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    ABSTRACT: Humans can reduce inorganic nitrate (NO(3)(-)) to nitrite (NO(2)(-)), nitric oxide (NO), and other bioactive nitrogen oxides. The purpose of this study was to test the hypothesis that a single dose of inorganic nitrate before exercise might enhance the tolerance of endurance athletes to high intensity exercise. Eleven cyclists (age = 34.3 ± 4.8 yr, VO(2peak) = 65.1 ± 6.2 mL·kg(-1)·min(-1)) participated in this randomized, double-blind, crossover study. Subjects received dietary supplementation with nitrate (NaNO(3) 10 mg·kg(-1) of body mass) or a placebo (NaCl) 3 h before exercise. They then performed a cycle ergometer test that consisted of four 6-min submaximal workloads, corresponding to 2.0, 2.5, 3.0, and 3.5 W·kg(-1) of body mass, interspersed with 3 min of passive recovery. After a 5-min recovery period, subjects performed one incremental exercise test until exhaustion. Plasma nitrate and nitrite were significantly higher (P < 0.05) 3 h after supplementation (nitrate = 250 ± 80 μM, nitrite = 2313 ± 157 nM) than after the placebo (nitrate = 29 ± 8 μM, nitrite = 1998 ± 206 nM) at resting conditions. Nitrate supplementation significantly reduced VO(2peak)(nitrate = 4.64 ± 0.35 L·min(-1), placebo = 4.82 ± 0.33 L·min(-1), P = 0.010) and the ratio between VO(2) and power at maximal intensity (nitrate = 11.2 ± 1.1 mL·min(-1)·W(-1), placebo = 11.8 ± 1.1 mL·min(-1)·W(-1), P = 0.031). This reduction of VO(2) occurred without changes in the time to exhaustion (nitrate = 416 ± 32 s, placebo = 409 ± 27 s) or in the maximal power (nitrate = 416 ± 29 W, placebo = 410 ± 28 W). A single oral dose of inorganic nitrate acutely reduces VO(2peak)without compromising the maximal exercise performance.
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    ABSTRACT: It has been hypothesized that l-arginine improves exercise performance by increasing nitric oxide synthesis and levels of insulin and growth hormone (GH). Metabolic and hormonal responses to chronic l-arginine supplementation may clarify the mechanisms underlying its putative physiologic effects on physical performance. Therefore, the aim of this study was to investigate the effects that 4 weeks of supplementation with l-arginine would have on metabolic and hormonal parameters at rest and in response to exercise. Fifteen healthy runners were divided into treatment (ARG; 6 g l-arginine) and placebo (PLA; 6 g cornstarch) groups. On the first visit, blood samples were collected for baseline, and the supplement or placebo was provided. After 4 weeks of supplementation (second visit), blood samples were collected at the following intervals: at rest, immediately after the first 5-km time-trial running test (5km-TT), immediately after the second 5km-TT, and after 20 minutes of recovery (+20). In addition to exercise performance (total running time), plasma nitrate, nitrite, nitrate plus nitrite, cyclic guanosine monophosphate, lactate, ammonia and serum insulin, GH, insulin-like growth factor 1, and cortisol concentrations were evaluated. There were significant increases in plasma nitrite, cyclic guanosine monophosphate, lactate, ammonia and serum GH, and cortisol at the first 5km-TT, immediately after the second 5km-TT, and +20 in both ARG and PLA. Nitrate plus nitrite and nitrate increased only at +20. No significant change was observed in serum insulin and insulin-like growth factor 1 in any sample period. Total running time did not differ significantly between the 2 tests, in either ARG or PLA. Thus, according to our results, 4 weeks of l-arginine supplementation did not cause beneficial changes in metabolic and hormonal parameters, beyond those achieved with exercise alone.
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