Stress biomarker changes following a series of repeated static and dynamic apneas in non-divers

Purpose This study examined the magnitude of physiological strain imposed by repeated maximal static and dynamic apneas through assessing a panel of stress-related biomarkers. Methods Eleven healthy men performed on three separate occasions (≥72-h apart): a series of five repeated maximal (i) static (STA) or (ii) dynamic apneas (DYN) or (iii) a static eupneic protocol (CTL). Venous blood samples were drawn at 30, 90, and 180-min after each protocol to determine ischaemia modified albumin (IMA), neuron-specific enolase (NSE), myoglobin, and high sensitivity cardiac troponin T (hscTnT) concentrations. Results IMA was elevated after the apnoeic interventions (STA,+86%;DYN,+332%,p ≤ 0.047) but not CTL (p = 0.385). Myoglobin was higher than baseline (23.6 ± 3.9 ng/mL) 30-min post DYN (+70%,38.8 ± 13.3 ng/mL,p = 0.030). A greater myoglobin release was recorded in DYN compared with STA and CTL (p ≤ 0.035). No changes were observed in NSE (p = 0.207) or hscTnT (p = 0.274). Conclusions Five repeated maximal DYN led to a greater muscle injury compared with STA but neither elicited myocardial injury or neuronal-parenchymal damage

Cutaneous exposure to hypoxia does not affect skin perfusion in humans.

$\textbf{Aim:}$ Experiments have indicated that skin perfusion in mice is sensitive to reductions in environmental O$_2$ availability. Specifically, a reduction in skin-surface PO$_2$ attenuates transcutaneous O$_2$ diffusion, and hence epidermal O$_2$ supply. In response, epidermal HIF-1$\alpha$ expression increases and facilitates initial cutaneous vasoconstriction and subsequent nitric oxide-dependent vasodilation. Here, we investigated whether the same mechanism exists in humans. $\textbf{Methods:}$ In a first experiment, eight males rested twice for 8 h in a hypobaric chamber. Once, barometric pressure was reduced by 50%, while systemic oxygenation was preserved by O$_2$-enriched (42%) breathing gas (Hypoxia$_\text{Skin}$), and once barometric pressure and inspired O$_2$ fraction were normal (Control$_1$). In a second experiment, nine males rested for 8 h with both forearms wrapped in plastic bags. O$_2$ was expelled from one bag by nitrogen flushing (Anoxia$_\text{Skin}$), whereas the other bag was flushed with air (Control$_2$). In both experiments, skin blood flux was assessed by laser Doppler on the dorsal forearm, and HIF-1$\alpha$ expression was determined by immunohistochemical staining in forearm skin biopsies. $\textbf{Results:}$ Skin blood flux during Hypoxia$_\text{Skin}$ and Anoxia$_\text{Skin}$ remained similar to the corresponding Control trial ($P$ = 0.67 and $P$ = 0.81). Immunohistochemically stained epidermal HIF-1$\alpha$ was detected on 8.2 ± 6.1 and 5.3 ± 5.7% of the analysed area during Hypoxia$_\text{Skin}$ and Control$_1$ ($P$ = 0.30) and on 2.3 ± 1.8 and 2.4 ± 1.8% during Anoxia$_\text{Skin}$ and Control$_2$ ($P$ = 0.90) respectively. $\textbf{Conclusion:}$ Reductions in skin-surface PO$_2$ do not affect skin perfusion in humans. The unchanged epidermal HIF-1$\alpha$ expression suggests that epidermal O$_2$ homoeostasis was not disturbed by Hypoxia$_\text{Skin}$/Anoxia$_\text{Skin}$, potentially due to compensatory increases in arterial O$_2$ extraction.Gösta Fraenckel Foundatio

Environmental Conditions, Air Pollutants, and Airways

Air pollution is a major problem worldwide, which could be even more serious for athletes who train in urban environments. Exercise increases minute ventilation and exposure to pollutants, but the literature on the effects of air pollution in athletes is relatively scarce, with the exception of chlorine exposure in athletes of aquatic sports and air pollution secondary to ice resurfacing in athletes performing in ice arenas. Although air pollution may exert detrimental effects on athletic performance, little has been published on this topic. The largest body of information regards the impact of air pollution during urban active transport, i.e., walking and cycling in cities, due to the potential risk of air pollution in citizens and the need to rethink urban transportation strategies accordingly. In healthy subjects, the benefits of physical activity largely outweigh the disadvantages of exposure to air pollutants. In susceptible individuals, however, such as patients with cardiac or respiratory disease and children, detrimental effects have been demonstrated. Improvement in air quality, individual protective behaviors, and prompt communication to the population of dangerous air quality may help to limit the negative effects of air pollution on respiratory health