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

Background: Human 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.

Methods: This 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 three.

Results: There 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.

Conclusion: An 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.



方法:これは、2群前向き無作為化二重盲検プラセボ対照試験であった。男性サイクリスト16名を、独自のサプリメント(Niteworks®、Herbalife International社、カリフォルニア州センチュリーシティ)またはプラセボ粉末のいずれかの摂取に無作為に割り付けた。運動パラメータは、固定サイクルエルゴメーターで行われた漸増負荷最大運動試験により、ベースライン時、及び第1週と第3週における呼吸ごとの分析を用いて評価した。

結果:ベースライン運動パラメータ間には差はなかった。サプリメント群では、無酸素性作業閾値は、第1週で16.7%(2.38±0.18 L/分、p < 0.01)増加し、効果は第3週まで14.2%(2.33±0.44 L/分、p < 0.01)で維持された。対照群では、無酸素性作業閾値は、第1週と第3週でベースラインと比較して変化はなかった(第1週で1.88±0.20 L/分、第3週で1.86±0.21 L/分)。サプリメント群の無酸素性作業閾値は、第1週と第3週でプラセボ群よりも有意に高かった。対照群と介入群の間にベースラインとの比較によるVO2 maxの有意な差は、第1週と第3週のいずれにおいても認められなかった。

結論:アルギニンと抗酸化物質含有サプリメントは、第1週と第3週の両方において高齢サイクリストの無酸素性作業閾値を上昇させた。VO2 maxに対する効果は認められなかった。この試験は、高齢者の運動パフォーマンスの向上におけるL-アルギニン及び酸化防止剤サプリメントの潜在的な役割を示した。