Abstract
Dietary nitrate (NIT) supplementation has been shown to increase nitric oxide (NO) metabolites and enhance exercise performance. Intriguingly, acute exposure to UVA light has also recently been shown to increase NO bioavailability although the effects on parameters of exercise performance are unknown.
PURPOSE: To determine the effects of UVA light alone and in combination with NIT supplementation on the physiological responses to submaximal exercise and cycling time trial (TT) performance.
METHODS: Nine trained cyclists (age 37 ± 6 yr, VO2max 53.1 ± 4.4 ml/kg/min) completed 5 cycling performance trials following an initial graded exercise test to exhaustion. Performance trials comprised 10 min cycling at 60% maximal work rate followed by a 16.1 km TT. The four remaining trials were preceded by one of four experimental interventions carried out in a randomised-crossover design: 1) UVA + NIT, 2) UVA + placebo (PLA), 3) Sham light (SHAM) + NIT and 4) SHAM + PLA. The NIT dose was 2 x 60 ml gels (∼8 mmol nitrate) or NIT-depleted PLA, ingested 2.75 h prior to the trial. The light exposure consisted of 20 min whole body irritation with either a UVA or SHAM source. VO2 was measured continuously during submaximal exercise and heart rate (HR) and stroke volume (SV) measured by pulse wave doppler at rest, 5 and 9 min. Differences between conditions were assessed by two-way ANOVA and paired t-tests. The magnitude of the difference was established with Cohen’s effect size.
RESULTS: VO2 was reduced following NIT + SHAM (P=0.043) and NIT + UVA (P=0.017) but not PLA + UVA (P=0.365) compared to PLA + SHAM. There was no difference in HR between conditions but SV was lower in PLA + UVA (P=0.024) and NIT + SHAM trials (P=0.034) compared to PLA + SHAM. TT performance was significantly faster following NIT + UVA, (1447 ± 41 s; P=0.004; d=0.44) but not PLA + UVA (1450 ± 40 s; d=0.37) or NIT + SHAM (1455 ± 47 s; d=0.28) compared to PLA + SHAM. However, magnitude based inferences suggest a small benefit of PLA + UVA, NIT + SHAM and NIT + UVA on TT performance.
CONCLUSIONS: We show for the first time that SV is reduced during submaximal exercise when NO bioavailability is increased. Furthermore, 20 min UVA exposure appears to produce a synergistic effect on reducing VO2 and enhancing TT performance when combined with NIT supplementation.
PURPOSE: To determine the effects of UVA light alone and in combination with NIT supplementation on the physiological responses to submaximal exercise and cycling time trial (TT) performance.
METHODS: Nine trained cyclists (age 37 ± 6 yr, VO2max 53.1 ± 4.4 ml/kg/min) completed 5 cycling performance trials following an initial graded exercise test to exhaustion. Performance trials comprised 10 min cycling at 60% maximal work rate followed by a 16.1 km TT. The four remaining trials were preceded by one of four experimental interventions carried out in a randomised-crossover design: 1) UVA + NIT, 2) UVA + placebo (PLA), 3) Sham light (SHAM) + NIT and 4) SHAM + PLA. The NIT dose was 2 x 60 ml gels (∼8 mmol nitrate) or NIT-depleted PLA, ingested 2.75 h prior to the trial. The light exposure consisted of 20 min whole body irritation with either a UVA or SHAM source. VO2 was measured continuously during submaximal exercise and heart rate (HR) and stroke volume (SV) measured by pulse wave doppler at rest, 5 and 9 min. Differences between conditions were assessed by two-way ANOVA and paired t-tests. The magnitude of the difference was established with Cohen’s effect size.
RESULTS: VO2 was reduced following NIT + SHAM (P=0.043) and NIT + UVA (P=0.017) but not PLA + UVA (P=0.365) compared to PLA + SHAM. There was no difference in HR between conditions but SV was lower in PLA + UVA (P=0.024) and NIT + SHAM trials (P=0.034) compared to PLA + SHAM. TT performance was significantly faster following NIT + UVA, (1447 ± 41 s; P=0.004; d=0.44) but not PLA + UVA (1450 ± 40 s; d=0.37) or NIT + SHAM (1455 ± 47 s; d=0.28) compared to PLA + SHAM. However, magnitude based inferences suggest a small benefit of PLA + UVA, NIT + SHAM and NIT + UVA on TT performance.
CONCLUSIONS: We show for the first time that SV is reduced during submaximal exercise when NO bioavailability is increased. Furthermore, 20 min UVA exposure appears to produce a synergistic effect on reducing VO2 and enhancing TT performance when combined with NIT supplementation.
| Original language | English |
|---|---|
| Pages (from-to) | 131 |
| Number of pages | 1 |
| Journal | Medicine and Science in Sports and Exercise |
| Volume | 46 |
| Issue number | 5s |
| DOIs | |
| Publication status | Published - May 2014 |