Static And Dynamic Grip Endurance At Altitude Is Not Affected By Acute Oral Sodium Nitrate Supplementation

There is increasing evidence that dietary nitrate (NO3-) supplementation improves exercise efficiency and performance. As the conversion of NO3- to nitrite to nitric oxide is facilitated by hypoxic and acidic conditions, NO3- supplementation may provide a useful means to prevent or mitigate altitude related decreases in exercise performance. PURPOSE: To determine if dynamic and static grip endurance performance in a hypobaric hypoxic environment is improved by acute oral administration of NO3-. METHODS: In a double-blind randomized, placebo-controlled cross-over design, 10 subjects (9 males, 1 female; mean ± SD age = 33.9 ± 9.7 years) were administered 500 ml of water containing either 20.4 mg/kg body weight of NaNO3 or the equivalent molar concentration of NaCl (placebo) prior to being exposed to 4,300 m of altitude in a hypobaric chamber. A static grip endurance test (SE = time held at 40% of the maximal voluntary static grip strength (MVC) with the left hand) and a dynamic grip endurance test (DE = 2 min periods of right handed cyclic contractions with a periodicity of 1 Hz separated by a 60 s rest period starting at 40% MVC and increasing by 10% MVC each step until exhaustion) were performed at 1) sea level pressure prior to drink administration, 2) 4,300 m of altitude 126 min (SE test) and 154 min (DE test) post drink administration, and 3) sea level post-altitude exposure 227 min (SE test) and 254 min (DE test) after drink administration. RESULTS: A repeated measure ANOVA revealed significant main effects of time for SE (p<0.05) and DE (p<0.001), but no significant main effects of drug or a drug x time interaction on either grip endurance test. Tukey’s post hoc analysis of the main effect of time demonstrated a significant 9.7% reduction in DE performance at altitude (p<0.001) and a trend for a 12.5% reduction in SE performance at altitude (p=0.054). CONCLUSIONS: Acute exposure to 4,300 m of altitude reduces dynamic and static grip endurance performance. The altitude mediated decreases in static and dynamic grip endurance are unaffected by acute oral NaNO3 supplementation. These results do not support acute oral administration of NaNO3 as a performance aid for tasks requiring forearm muscular endurance at high altitude.

Duke Scholars

Author Heath Gasier Anesthesiology