An acute dose of inorganic dietary nitrate does not improve high-intensity, intermittent exercise performance in temperate or hot and humid conditions

Kieran Smith, David J. Muggeridge, Chris Easton, Mark D. Ross

Research output: Contribution to journalArticle

Abstract

Purpose
Exercise in hot and humid conditions augments a rise in core body temperature, leading to premature fatigue and performance impairments. Dietary nitrate (NO3-) has repeatedly been shown to improve self-paced endurance and intermittent, high-intensity events in ambient conditions. However, the ergogenic effects of dietary NO3- on intermittent exercise performance in hot conditions has yet to be investigated.

Methods
In a randomised, counterbalanced, double-blind crossover study, twelve trained males ingested a nitrate-rich beetroot juice shot (BRJ) (8.2 mmol NO3-) or a nitrate-depleted placebo (PLA) (<0.004mmol NO3-) 3h prior to an intermittent sprint test (IST) in ambient (22°C, 35% RH) and hot conditions (30°C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6s sprints interspersed by 114s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion.

Results
There were no significant trial x time effects were found on sprint performance in either ambient or hot, humid conditions (p>0.05). There was a reduced peak (BRJ: 659±100W vs. PLA: 693±139W; p=0.056; d=0.28) and mean power (BRJ: 543 ± 29W vs PLA: 575 ± 38W; p=0.081; d=0.27) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done (ambient: p = 0.447, d = 0.07, hot and humid: p = 0.101, d = 0.28) irrespective of environmental condition. However, ~75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial (BRJ: 37.3 ± 0.7°C vs PLA: 37.3 ± 0.6°C; p=0.93).

Conclusion
In conclusion, an acute dose of inorganic dietary NO3- does not improve repeated sprint performance in either ambient, or hot and humid conditions.
Original languageEnglish
Number of pages11
JournalEuropean Journal of Applied Physiology
Early online date8 Jan 2019
DOIs
Publication statusE-pub ahead of print - 8 Jan 2019

Fingerprint

Nitrates
Placebos
Performance-Enhancing Substances
Body Temperature
Double-Blind Method
Cross-Over Studies
Fatigue
High-Intensity Interval Training
Temperature

Keywords

  • Nitrate
  • Exercise
  • Heat
  • High-intensity
  • Beetroot juice
  • Humidity

Cite this

@article{cbbd7a81493343db9db8a715e457a0e6,
title = "An acute dose of inorganic dietary nitrate does not improve high-intensity, intermittent exercise performance in temperate or hot and humid conditions",
abstract = "PurposeExercise in hot and humid conditions augments a rise in core body temperature, leading to premature fatigue and performance impairments. Dietary nitrate (NO3-) has repeatedly been shown to improve self-paced endurance and intermittent, high-intensity events in ambient conditions. However, the ergogenic effects of dietary NO3- on intermittent exercise performance in hot conditions has yet to be investigated. MethodsIn a randomised, counterbalanced, double-blind crossover study, twelve trained males ingested a nitrate-rich beetroot juice shot (BRJ) (8.2 mmol NO3-) or a nitrate-depleted placebo (PLA) (<0.004mmol NO3-) 3h prior to an intermittent sprint test (IST) in ambient (22°C, 35{\%} RH) and hot conditions (30°C, 70{\%} RH). The cycle ergometer IST consisted of twenty maximal 6s sprints interspersed by 114s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion. ResultsThere were no significant trial x time effects were found on sprint performance in either ambient or hot, humid conditions (p>0.05). There was a reduced peak (BRJ: 659±100W vs. PLA: 693±139W; p=0.056; d=0.28) and mean power (BRJ: 543 ± 29W vs PLA: 575 ± 38W; p=0.081; d=0.27) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done (ambient: p = 0.447, d = 0.07, hot and humid: p = 0.101, d = 0.28) irrespective of environmental condition. However, ~75{\%} of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial (BRJ: 37.3 ± 0.7°C vs PLA: 37.3 ± 0.6°C; p=0.93). ConclusionIn conclusion, an acute dose of inorganic dietary NO3- does not improve repeated sprint performance in either ambient, or hot and humid conditions.",
keywords = "Nitrate, Exercise, Heat, High-intensity, Beetroot juice, Humidity",
author = "Kieran Smith and Muggeridge, {David J.} and Chris Easton and Ross, {Mark D.}",
year = "2019",
month = "1",
day = "8",
doi = "10.1007/s00421-018-04063-9",
language = "English",
journal = "European Journal of Applied Physiology",
issn = "1439-6319",
publisher = "Springer-Verlag",

}

TY - JOUR

T1 - An acute dose of inorganic dietary nitrate does not improve high-intensity, intermittent exercise performance in temperate or hot and humid conditions

AU - Smith, Kieran

AU - Muggeridge, David J.

AU - Easton, Chris

AU - Ross, Mark D.

PY - 2019/1/8

Y1 - 2019/1/8

N2 - PurposeExercise in hot and humid conditions augments a rise in core body temperature, leading to premature fatigue and performance impairments. Dietary nitrate (NO3-) has repeatedly been shown to improve self-paced endurance and intermittent, high-intensity events in ambient conditions. However, the ergogenic effects of dietary NO3- on intermittent exercise performance in hot conditions has yet to be investigated. MethodsIn a randomised, counterbalanced, double-blind crossover study, twelve trained males ingested a nitrate-rich beetroot juice shot (BRJ) (8.2 mmol NO3-) or a nitrate-depleted placebo (PLA) (<0.004mmol NO3-) 3h prior to an intermittent sprint test (IST) in ambient (22°C, 35% RH) and hot conditions (30°C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6s sprints interspersed by 114s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion. ResultsThere were no significant trial x time effects were found on sprint performance in either ambient or hot, humid conditions (p>0.05). There was a reduced peak (BRJ: 659±100W vs. PLA: 693±139W; p=0.056; d=0.28) and mean power (BRJ: 543 ± 29W vs PLA: 575 ± 38W; p=0.081; d=0.27) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done (ambient: p = 0.447, d = 0.07, hot and humid: p = 0.101, d = 0.28) irrespective of environmental condition. However, ~75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial (BRJ: 37.3 ± 0.7°C vs PLA: 37.3 ± 0.6°C; p=0.93). ConclusionIn conclusion, an acute dose of inorganic dietary NO3- does not improve repeated sprint performance in either ambient, or hot and humid conditions.

AB - PurposeExercise in hot and humid conditions augments a rise in core body temperature, leading to premature fatigue and performance impairments. Dietary nitrate (NO3-) has repeatedly been shown to improve self-paced endurance and intermittent, high-intensity events in ambient conditions. However, the ergogenic effects of dietary NO3- on intermittent exercise performance in hot conditions has yet to be investigated. MethodsIn a randomised, counterbalanced, double-blind crossover study, twelve trained males ingested a nitrate-rich beetroot juice shot (BRJ) (8.2 mmol NO3-) or a nitrate-depleted placebo (PLA) (<0.004mmol NO3-) 3h prior to an intermittent sprint test (IST) in ambient (22°C, 35% RH) and hot conditions (30°C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6s sprints interspersed by 114s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion. ResultsThere were no significant trial x time effects were found on sprint performance in either ambient or hot, humid conditions (p>0.05). There was a reduced peak (BRJ: 659±100W vs. PLA: 693±139W; p=0.056; d=0.28) and mean power (BRJ: 543 ± 29W vs PLA: 575 ± 38W; p=0.081; d=0.27) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done (ambient: p = 0.447, d = 0.07, hot and humid: p = 0.101, d = 0.28) irrespective of environmental condition. However, ~75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial (BRJ: 37.3 ± 0.7°C vs PLA: 37.3 ± 0.6°C; p=0.93). ConclusionIn conclusion, an acute dose of inorganic dietary NO3- does not improve repeated sprint performance in either ambient, or hot and humid conditions.

KW - Nitrate

KW - Exercise

KW - Heat

KW - High-intensity

KW - Beetroot juice

KW - Humidity

U2 - 10.1007/s00421-018-04063-9

DO - 10.1007/s00421-018-04063-9

M3 - Article

JO - European Journal of Applied Physiology

JF - European Journal of Applied Physiology

SN - 1439-6319

ER -