Skin tattooing impairs sweating during passive whole body heating.

Tattooing of the skin involves repeated needle insertions to deposit ink into the dermal layer of the skin, potentially damaging eccrine sweat glands and the cutaneous vasculature. This study tested the hypothesis that reflex increases in sweat rate (SR) and cutaneous vasodilation are blunted in tattooed skin (TAT) compared with adjacent healthy skin (CON) during a passive whole body heat stress (WBH). Ten individuals (5 males and 5 females) with a sufficient area of tattooed skin participated in the study. Intestinal temperature (Tint), skin temperature (Tskin), skin blood flow (laser Doppler flux; LDF), and SR were continuously measured during normothermic baseline (34°C water perfusing a tube-lined suit) and WBH (increased Tint 1.0°C via 48°C water perfusing suit). SR throughout WBH was lower for TAT compared with CON (P = 0.033). Accumulated sweating responses during WBH (area under curve) were attenuated in TAT relative to CON (23.1 ± 12.9, 26.9 ± 14.5 mg/cm2, P = 0.043). Sweating threshold, expressed as the onset of sweating in time or Tint from the initiation of WBH, was not different between TAT and CON. Tattooing impeded the ability to obtain LDF measurements. These data suggest that tattooing functionally damages secretion mechanisms, affecting the reflex capacity of the gland to produce sweat, but does not appear to affect neural signaling to initiate sweating. Decreased sweating could impact heat dissipation especially when tattooing covers a higher percentage of body surface area and could be considered a potential long-term clinical side effect of tattooing.NEW & NOTEWORTHY This study is the first to assess the reflex control of sweating in tattooed skin. The novel findings are twofold. First, attenuated increases in sweat rate were observed in tattooed skin compared with adjacent healthy non-tattooed skin in response to a moderate increase (1.0°C) in internal temperature during a passive whole body heat stress. Second, reduced sweating in tattooed skin is likely related to functional damage to the secretory mechanisms of eccrine sweat glands, rendering it less responsive to cholinergic stimulation.

The effects of ad libitum fluid ingestion on fluid balance during alpine skiing in recreational skiers.

The aim of this study was to assess the influence of ad libitum water ingestion, using a back-mounted hydration system (BMHS), on fluid balance during alpine skiing. Fourteen skiers skied on two different days. On one day, seven skiers ingested water during skiing via the BMHS and the other seven skiers refrained from fluid ingestion during skiing until the midday break (NW trial). On the second day, the trials were reversed. Results indicated that when skiers used the BMHS they drank significantly more water than during the NW trials (2.0 +/- 0.9 vs. 0.78 +/- 0.4 litres). However, skiers drank significantly more at the midday break during the NW trials than during the BMHS trials (0.78 +/- 0.4 vs. 0.4 +/- 0.2 litres). Percent change in plasma volume was less during the BMHS trials than during the NW trials (-0.1 +/- 5.3 vs. -4.9 +/- 5.2%), urine osmolality was maintained in the BMHS trials but rose from 295 +/- 80 to 818 +/- 168 mOsm . kg(-1) at midday during the NW trials, and body mass loss was minimized during the BMHS trials compared with the NW trials (0.4 +/- 0.4 vs. 1.1 +/- 0.2 kg). Skiers reported that they felt significantly better when they ingested water during the BMHS trials. In conclusion, a back-mounted hydration system allowed the skiers to maintain hydration status.

Lack of effect of Rhodiola or oxygenated water supplementation on hypoxemia and oxidative stress.

OBJECTIVE: This study investigated the effects of 2 potentially "oxygen promoting" dietary supplements on hypoxia and oxidative stress at a simulated altitude of 4600 m. METHODS: Fifteen volunteers (ages 20-33) received 3 separate 60-minute hypoxic exposures by breathing 13.6% oxygen at an ambient barometric pressure of 633 mm Hg (simulating the partial pressure of oxygen at 4600 m elevation). Each subject received, in random order, treatments of a 7-day supply of placebo, Rhodiola rosea, and an acute dose of stabilized oxygen dissolved in water. Arterialized capillary blood oxygen samples (PcO2) were measured at baseline and at 30 and 60 minutes of exposure. Pulse oximeter oxyhemoglobin saturation (SaO2) was measured at baseline and at every 10 minutes of hypoxic exposure. Oxidative stress markers measured included baseline and 60-minute exposure serum lipid peroxides (LPO) and urine malondialdehyde (MDA). RESULTS: For each treatment group, PcO2 decreased by approximately 38% from baseline to 60-minute hypoxic exposure. Similarly, SaO2 also decreased among groups from approximately 97 to 81%. Serum lipid peroxides increased significantly in the placebo group and decreased significantly from baseline in response to the stabilized oxygen treatment (P = .02); there was a trend for decreased LPO with the Rhodiola treatment (P = .10). There were no significant changes for MDA among groups. CONCLUSIONS: The 2 dietary supplements investigated did not have a significant effect on blood oxygenation after 60 minutes of sedentary hypoxic exposure. Hypoxia-induced oxidative stress was observed in the control group only. Both supplements appeared not to increase oxidative stress and may decrease free radical formation after hypoxic exposure compared with the control.

Thermal regulatory responses to submaximal cycling following lower-body cooling in humans.

This study compared the effects of pre-exercise cooling with control water immersions on exercise-induced thermal loads derived from steady-state submaximal exercise. Eight healthy male participants [mean (SEM) age 29 (1) years, maximal oxygen uptake 3.81 (0.74) l x min(-1), and body surface area 1.85 (0.11) m(2)] took part in experiments that included 30 min of baseline data collection [ambient temperature 21.3 (0.2 degrees C)], 30 min of immersion in water to the level of the supra-iliac crest [water temperatures of 35.1 (0.3) degrees C for thermoneutral and 17.7 (0.5) degrees C for precooled treatments], and 60 min of cycling exercise at 60% of maximal oxygen uptake. No significant differences were noted during exercise in net mechanical efficiency, metabolic rate, O(2) pulse, or ratings of perceived exertion between the two treatments. Precooling resulted in a significant negative body heat storage during immersion and allowed greater heat storage during exercise. However, net body heat storage for the entire protocol was no different between treatments. Cooling significantly lowered rectal, mean skin, and mean body temperatures as well as more than doubling the exercise time until a 0.5 degrees C rectal temperature increase was observed. The cooling trial significantly delayed onset of sweating by 19.62 min and decreased sweat rate by 255 ml x h(-1) compared to control. Thermal and sweat sensation scores were lower after the cooling treatment compared to control. These data suggest that lower-body precooling is effective at decreasing body heat storage prior to exercise and decreases reliance on heat dissipation mechanisms during exercise. Therefore, this unique, well-tolerated cooling treatment should have a broader application than other precooling treatments.