The influence of acute dietary nitrate supplementation on skeletal muscle fatigue and recovery in older women

Older individuals fatigue more rapidly during, and recover more slowly from, dynamic exercise. Women are particularly vulnerable to these deleterious effects of aging, which increases their risk of falling. We have shown that dietary nitrate (NO3-), a source of nitric oxide (NO) via the NO3- -> nitrite (NO2-) -> NO pathway, enhances muscle speed and power in older individuals in the non-fatigued state; however, it is unclear if it reduces fatigability and/or improves recoverability in this population. Using a double-blind, placebo-controlled, crossover design, we studied 18 older (age 70 +/- 4 years) women who were administered an acute dose of beetroot juice (BRJ) containing either 15.6 +/- 3.6 or <0.05 mmol of NO3-. Blood samples were drawn throughout each similar to 3 h visit for plasma NO3- and NO2- analysis. Peak torque was measured during, and periodically for 10 min after, 50 maximal knee extensions performed at 3.14 rad/s on an isokinetic dynamometer. Ingestion of NO3--containing BRJ increased plasma NO3- and NO2- concentrations by 21 +/- 8 and 4 +/- 4 fold, respectively. However, there were no differences in muscle fatigue or recovery. Dietary NO3- increases plasma NO3- and NO2- concentrations but does not reduce fatigability during or enhance recoverability after high intensity exercise in older women.