title: Acute whole body UVA irradiation combined with nitrate ingestion enhances time trial performance in trained cyclists.
abstract: Dietary nitrate supplementation has been shown to increase nitric oxide (NO) metabolites, reduce blood pressure (BP) and enhance exercise performance. Acute exposure to ultraviolet (UV)-A light also increases NO bioavailability and reduces BP. We conducted a randomized, counterbalanced placebo-controlled trial to determine the effects of UV-A light alone and in combination with nitrate on the responses to sub-maximal steady-state exercise and time trial (TT) performance. Nine cyclists (VO2max 53.1 ± 4.4 ml/kg/min) completed five performance trials comprising 10 min submaximal steady-state cycling followed by a 16.1 km TT. Following a familiarization the final four trials were preceded, in random order, by either (1) Nitrate gels (NIT) + UV-A, (2) Placebo (PLA) + UV-A, (3) NIT + Sham light (SHAM) and (4) PLA + SHAM (control). The NIT gels (2 × 60 ml gels, ~8.1 mmol nitrate) or a low-nitrate PLA were ingested 2.5 h prior to the trial. The light exposure consisted of 20 J/cm(2) whole body irradiation with either UV-A or SHAM light. Plasma nitrite was measured pre- and post-irradiation and VO2 was measured continuously during steady-state exercise. Plasma nitrite was higher for NIT + SHAM (geometric mean (95% CI), 332 (292-377) nM; P = 0.029) and NIT + UV-A (456 (312-666) nM; P = 0.014) compared to PLA + SHAM (215 (167-277) nM). Differences between PLA + SHAM and PLA + UV-A (282 (248-356) nM) were small and non-significant. During steady-state exercise VO2 was reduced following NIT + UVA (P = 0.034) and tended to be lower in NIT + SHAM (P = 0.086) but not PLA + UV-A (P = 0.381) compared to PLA + SHAM. Performance in the TT was significantly faster following NIT + UV-A (mean ± SD 1447 ± 41 s P = 0.005; d = 0.47), but not PLA + UV-A (1450 ± 40 s; d = 0.41) or NIT + SHAM (1455 ± 47 s; d = 0.28) compared to PLA + SHAM (1469 ± 52 s). These findings demonstrate that exposure to UV-A light alone does not alter the physiological responses to exercise or improve performance in a laboratory setting. A combination of UV-A and NIT, however, does improve cycling TT performance in this environment, which may be due to a larger increase in NO availability.
authors.affiliation: Institute for Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Muggeridge
authors.affiliation: Institute for Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Sculthorpe
authors.affiliation: Institute for Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, UK.
authors.forename: Fergal M
authors.initials: FM
authors.lastname: Grace
authors.affiliation: Wales Heart Research Institute, Cardiff University Medical School, Cardiff, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Willis
authors.affiliation: Wales Heart Research Institute, Cardiff University Medical School, Cardiff, UK.
authors.forename: Laurence
authors.initials: L
authors.lastname: Thornhill
authors.affiliation: Department of Dermatology, University of Edinburgh, Edinburgh, UK; MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, UK.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Weller
authors.affiliation: Wales Heart Research Institute, Cardiff University Medical School, Cardiff, UK.
authors.forename: Philip E
authors.initials: PE
authors.lastname: James
authors.affiliation: Institute for Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, UK. Electronic address: chris.easton@uws.ac.uk.
authors.forename: Chris
authors.initials: C
authors.lastname: Easton
mesh_terms: D000328:Adult; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology; D005782:Gels / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009566:Nitrates / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D009573:Nitrites / Q000097:blood; D013472:Sunlight; D014466:Ultraviolet Rays
chemical_list: D005782:Gels; D009566:Nitrates; D009573:Nitrites
keywords: Exercise; Nitric oxide; Nitrite