The effect of carbohydrate ingestion on the Interleukin-6 response to a 90-minute run time trial

Fatigue is a predictable outcome of prolonged physical activity; yet its biological cause remains uncertain. During exercise, a polypeptide messenger molecule interleukin- 6 (IL-6) is actively produced. Previously, it has been demonstrated that administration of recombinant IL-6 (rhIL-6) impairs 10-km run performance and heightened sensation of fatigue in trained runners. Both high carbohydrate diets and carbohydrate ingestion during prolonged exercise have a blunting effect on IL-6 levels postendurance exercise. We hypothesized that carbohydrate ingestion may improve performance during a prolonged bout of exercise as a consequence of a blunted IL-6 response. Seven recreationally trained fasted runners completed two 90-min time trials under CHO supplemented and placebo conditions in a randomized order. The study was of a double-blinded, placebo-controlled, cross-over study design. Distance covered in 90 min was significantly greater following exogenous carbohydrate ingestion compared with the placebo trial (19.13 ± 1.7 km and 18.29 ± 1.9 km, respectively, p = .0022). While postexercise IL-6 levels were significantly lower in the CHO trial compared with the placebo trial (5.3 ± 1.9 pg·mL?1and 6.6 ± 3.0 pg·mL?1, respectively; p = .0313), this difference was considered physiologically too small to mediate the improvement in time trial performance

Skin blood flow responses to locally applied acetylcholine in Caucasian and African descent individuals with and without cyclooxygenase inhibition

Individuals of African descent (AFD) are more susceptible to non-freezing cold injury (NFCI) than Caucasians (CAU) [1]. This may be a consequence of lower skin blood flow during local cold exposure and subsequent rewarming in AFD [2], possibly due to a difference in endothelium function as acet ylcholine (ACh)-induced vasodilatation is smaller in AFD than CAU on the non-glabrous finger and toe skin sites [3]. It is known that prostaglandins produced by the enzyme cyclooxygenase (COX) mediate part of the ACh-induced vasodilator response [4] however in hypertensive individuals, COX inhibition results in augmented vasodilatation in response to ACh [5] demonstrating that COX can also promote vasoconstriction. Whether COX products are involved in the attenuated vasodilator response to ACh in healthy AFD [3] is not known. Therefore, the aim of the present study was to investigate the contribution of COX in both CAU and AFD to local application of ACh in foot and finger skin sites which are susceptible to NFCI

Effects of dietary nitrate supplementation on the response to extremity cooling and endothelial function in individuals with cold sensitivity. A double blind, placebo controlled, crossover, randomised control trial

Individuals with cold sensitivity have low peripheral skin blood flow and skin temperature possibly due to reduced nitric oxide (NO•) bioavailability. Beetroot has a high concentration of inorganic nitrate and may increase NO-mediated vasodilation. Using a placebo-controlled, double blind, randomised, crossover design, this study tested the hypotheses that acute beetroot supplementation would increase the rate of cutaneous rewarming following a local cold challenge and augment endothelium-dependent vasodilation in cold sensitive individuals. Thirteen cold sensitive participants completed foot and hand cooling (separately, in 15 °C water for 2 minutes) with spontaneous rewarming in 30°C air whilst skin temperature and cutaneous vascular conductance (CVC) were measured (Baseline). On two further separate visits, participants consumed 140 ml of either concentrated beetroot juice (nitrate supplementation) or nitrate-depleted beetroot juice (Placebo) 90 minutes before resting seated blood pressure was measured. Endothelial function was assessed by measuring CVC at the forearm, finger and foot during iontophoresis of 1% w/v acetylcholine followed by foot and hand cooling as for Baseline. Plasma nitrite concentrations significantly increased in nitrate supplementation compared to Placebo and Baseline (502 ± 246 nmol.L-1; 73 ± 45 nmol.L-1; 74 ± 49 nmol.L-1 respectively; n=11; P 0.05). Nitrate supplementation did not alter endothelial function in the forearm, finger or foot (all P > 0.05) compared to Placebo. Despite a physiologically meaningful rise in plasma nitrite concentrations, acute nitrate supplementation does not alter extremity rewarming, endothelial function or blood pressure in individuals with cold sensitivity

The physiology of paragliding flight at moderate and extreme altitudes

This is the author accepted manuscript. The final version is available from Mary Ann Liebert via the DOI in this recordThe physiology of paragliding flight at moderate and extreme altitudes. High Alt Med Biol 00:000–000, 2017.—Paragliding is a form of free flight, with extreme-altitude paragliding being an emerging discipline. We aimed to describe the physiological demands and the impact of environmental stressors of paragliding at moderate and extreme altitudes. We recorded oxygen consumption (VO2), heart rate (HR), respiratory frequency (fR), tidal volume (VT), oxygen saturation, accelerometry (G), and altitude in 9.3 hours of flight at moderate altitudes (to 3073 m, n = 4), 19.3 hours at extreme altitude (to 7458 m, n = 2), and during high-G maneuvers (n = 2). We also analyzed HR data from an additional 17 pilots (138 hours) using the Flymaster Live database to corroborate our findings. All pilots were male. Overall energy expenditure at moderate altitude was low [1.7 (0.6) metabolic equivalents], but physiological parameters were notably higher during takeoff (p < 0.05). Pilots transiently reached ∼7 G during maneuvers. Mean HR at extreme altitude [112 (14) bpm] was elevated compared to moderate altitude [98 (15) bpm, p = 0.048]. Differences in pilots' VT and fR at moderate and extreme altitudes were not statistically significant (p = 0.96 and p = 0.058, respectively). Thus, we conclude that physical exertion in paragliding is low, suggesting that any subjective fatigue felt by pilots is likely to be cognitive or environmental. Future research should focus on reducing mental workload, enhancing cognitive function, and improving environmental protection.Equipment for the study was provided by the University of Portsmouth Department of Sports Science, the University of Exeter Link Fund Award and Research QR uplift fund. We gratefully acknowledge the assistance of Dr Juliana Pugmire (University of Glasgow) for review of the manuscript and advice regarding statistical analysis; Professor Adrian Thomas, Professor Sue Ward, Dr Pete Hodkinson, Dr Bonnie Posselt, Dr Tom Yeoman, Dr Ellie Heath; The Free Flight Physiology Project; CASE Medicine; Escape Paragliding, Ozone Chabre Open, SEARCH Projects, Flyeo, Flymaster Avionics and all the pilots who kindly volunteered to take part

Infrared cameras overestimate skin temperature during rewarming from cold exposure

This is an accepted manuscript of an article published by Elsevier in Journal of Thermal Biology on 03/05/2020, available online: https://doi.org/10.1016/j.jtherbio.2020.102614 The accepted version of the publication may differ from the final published version.Objective The primary aim of this study was to assess the accuracy of an infrared camera and that of a skin thermistor, both commercially available. The study aimed to assess the agreement over a wide range of skin temperatures following cold exposure. Methods Fifty-two males placed their right hand in a thin plastic bag and immersed it in 8 °C water for 30 min whilst seated in an air temperature of 30 °C. Following hand immersion, participants removed the bag and rested their hand at heart level for 10 min. Index finger skin temperature (Tsk) was measured with a thermistor, affixed to the finger pad, and an infrared camera measured 1 cm distally to the thermistor. Agreement between the infrared camera and thermistor was assessed by mean difference (infrared camera minus thermistor) and 95% limits of agreement analysis, accounting for the repeated measures over time. The clinically significant threshold for Tsk differences was set at ±0.5 °C and limits of agreement ±1 °C. Results As an average across all time points, the infrared camera recorded Tsk 1.80 (SD 1.16) °C warmer than the thermistor, with 95% limits of agreement ranging from −0.46 °C to 4.07 °C. Conclusion Collectively, the results show the infrared camera overestimated Tsk at every time point following local cooling. Further, measurement of finger Tsk from the infrared camera consistently fell outside the acceptable level of agreement (i.e. mean difference exceeding ±0.5 °C). Considering these results, infrared cameras may overestimate peripheral Tsk following cold exposure and clinicians and practitioners should, therefore, adjust their risk/withdrawal criteria accordingly.Published versio

Role of cyclooxygenase in the vascular responses to extremity cooling in Caucasian and African males

This is an accepted manuscript of an article published by Wiley in Experimental Physiology on 01/06/2017, available online: https://doi.org/10.1113/EP086186 The accepted version of the publication may differ from the final published version.© 2017 The Authors. Experimental Physiology © 2017 The Physiological Society New Findings: What is the central question of this study? Compared with Caucasians, African individuals are more susceptible to non-freezing cold injury and experience greater cutaneous vasoconstriction and cooler finger skin temperatures upon hand cooling. We investigated whether the enzyme cyclooxygenase is, in part, responsible for the exaggerated response to local cooling. What is the main finding and its importance? During local hand cooling, individuals of African descent experienced significantly lower finger skin blood flow and skin temperature compared with Caucasians irrespective of cyclooxygenase inhibition. These data suggest that in young African males the cyclooxygenase pathway appears not to be the primary reason for the increased susceptibility to non-freezing cold injury. Individuals of African descent (AFD) are more susceptible to non-freezing cold injury (NFCI) and experience an exaggerated cutaneous vasoconstrictor response to hand cooling compared with Caucasians (CAU). Using a placebo-controlled, cross-over design, this study tested the hypothesis that cyclooxygenase (COX) may, in part, be responsible for the exaggerated vasoconstrictor response to local cooling in AFD. Twelve AFD and 12 CAU young healthy men completed foot cooling and hand cooling (separately, in 8°C water for 30 min) with spontaneous rewarming in 30°C air after placebo or aspirin (COX inhibition) treatment. Skin blood flow, expressed as cutaneous vascular conductance (as flux per millimetre of mercury), and skin temperature were measured throughout. Irrespective of COX inhibition, the responses to foot cooling, but not hand cooling, were similar between ethnicities. Specifically, during hand cooling after placebo, AFD experienced a lower minimal skin blood flow [mean (SD): 0.5 (0.1) versus 0.8 (0.2) flux mmHg−1, P < 0.001] and a lower minimal finger skin temperature [9.5 (1.4) versus 10.7 (1.3)°C, P = 0.039] compared with CAU. During spontaneous rewarming, average skin blood flow was also lower in AFD than in CAU [2.8 (1.6) versus 4.3 (1.0) flux mmHg−1, P < 0.001]. These data provide further support that AFD experience an exaggerated response to hand cooling on reflection this appears to overstate findings; however, the results demonstrate that the COX pathway is not the primary reason for the exaggerated responses in AFD and increased susceptibility to NFCI.This research was funded by the University of Portsmouth.Published versio