25We hypothesized that acute dietary nitrate (NO3 -) provided as concentrated beetroot juice 26 supplement would improve endurance running performance of well-trained runners in 27 normobaric hypoxia. Ten male runners (mean (SD): sea level V O2max 66 (7) mL . kg -1. min -1 , 10 28 km personal best 36 (2) min) completed incremental exercise to exhaustion at 4000 m and a 10 29 km treadmill time trial at 2500 m simulated altitude on separate days, after supplementation 30 with ~7 mmol NO3 -and a placebo, 2.5 h before exercise. Oxygen cost, arterial oxygen 31 saturation, heart rate and ratings of perceived exertion (RPE) were determined during the 32 incremental exercise test. Differences between treatments were determined using means [95% 33confidence intervals], paired sample t-tests and a probability of individual response analysis.

The effectiveness of a nap as a recovery strategy for endurance exercise is unknown and therefore the present study investigated the effect of napping on endurance exercise performance. Eleven trained male runners completed this randomised crossover study. On two occasions, runners completed treadmill running for 30 min at 75% ⩒O in the morning, returning that evening to run for 20 min at 60% ⩒O, and then to exhaustion at 90% ⩒O. On one trial, runners had an afternoon nap approximately 90 min before the evening exercise (NAP) whilst on the other, runners did not (CON). All runners napped (20 ± 10 min), but time to exhaustion (TTE) was not improved in all runners (NAP 596 ± 148 s vs. CON 589 ± 216 s, P = .83). Runners that improved TTE after the nap slept less at night than those that did not improve TTE (night-time sleep 6.4 ± 0.7 h vs. 7.5 ± 0.4 h, P < .01). Furthermore, night-time sleep predicted change in TTE, indicating that runners sleeping least at night improved TTE the most after the nap compared to CON (r = -0.76, P = .001). In runners that improved TTE, ratings of perceived exertion (RPE) were lower during the TTE on NAP than CON compared to runners that did not improve (-0.4 ± 0.6 vs. 0 ± 0, P = .05). Reduced exercising sense of effort (RPE) may account for the improved TTE after the nap. In conclusion, a short afternoon nap improves endurance performance in runners that obtain less than 7 h night-time sleep.