Extreme Physiology & Medicine - Latest Articles

Cold sensitivity test for individuals with non-freezing cold injury: the effect of prior exercise

Clare Eglin — 2013-05-01T00:00:00Z

Background: One of the chronic symptoms of non-freezing cold injury (NFCI) is cold sensitivity. This study examined the effects of prior exercise on the response to a cold sensitivity test (CST) in NFCI patients with the aim of improving diagnostic accuracy. Methods: Twenty three participants, previously diagnosed with NFCI by a Cold Injuries Clinic, undertook two CSTs. Participants either rested (air temperature 31[degree sign]C) for approximately 80 min (prior rest condition (REST)) or rested for 30 min before exercising gently for 12 min (prior exercise condition (EX)). Following REST and EX, the participants placed their injured foot, covered in a plastic bag, into 15[degree sign]C water for 2 min; this was followed by spontaneous rewarming in 31[degree sign]C air for 10 min. Results: The great toe skin temperature (Tsk) before immersion averaged 32.5 (3.4)[degree sign]C in both conditions. Following immersion, the rate of rewarming of the great toe Tsk was faster in EX compared to REST and was higher 5 min (31.7 (3.4)[degree sign]C vs. 29.8 (3.4)[degree sign]C) and 10 min (33.8 (4.0)[degree sign]C vs. 32.0 (4.0)[degree sign]C) post-immersion. Over the first 5 min of rewarming, changes in the great toe Tsk correlated with the changes in skin blood flow (SkBF) in EX but not the REST condition. No relationship was observed between Tsk in either CST and the severity of NFCI as independently clinically assessed. Conclusions: Exercise prior to the CST increased the rate of the toe Tsk rewarming, and this correlated with the changes in SkBF. However, the CST cannot be used in isolation in the diagnosis of NFCI, although the EX CST may prove useful in assessing the severity of post-injury cold sensitivity for prognostic and medico-legal purposes.

Participation and performance trends in ultra-endurance running races under extreme conditions - `Spartathlon¿ versus `Badwater¿

Kristina da Fonseca-Engelhardt — 2013-05-01T00:00:00Z

Background: The aim of the present study was to compare the trends in participation, performance and age of finishers in ‘Badwater’ and ‘Spartathlon’ as two of the toughest ultramarathons in the world of more than 200 km of distance. Methods: Running speed and age of male and female finishers in Badwater and Spartathlon were analyzed from 2000 to 2012. Age of peak performance and sex difference in running speed were investigated during the studied period. Results: The number of female and male finishes increased in Badwater and Spartathlon. Women accounted on average for 21.5% ± 6.9% in Badwater and 10.8% ± 2.3% in Spartathlon. There was a significant increase in female participation in Badwater from 18.4% to 19.1% (p < 0.01) and in Spartathlon from 11.9% to 12.5% (p = 0.02). In men, the age of finishers was higher in Badwater (46.5 ± 9.3 years) compared to Spartathlon (44.8 ± 8.2 years) (p < 0.01). The age of female finishers of both races was similar with 43.0 ± 7.5 years in Badwater and 44.5 ± 7.8 years in Spartathlon (p > 0.05). Over the years, the age of the annual five fastest men decreased in Badwater from 42.4 ± 4.2 to 39.8 ± 5.7 years (p < 0.05). For women, the age remained unchanged at 42.3 ± 3.8 years in Badwater (p > 0.05). In Spartathlon, the age was unchanged at 39.7 ± 2.4 years for men and 44.6 ± 3.2 years for women (p > 0.05). In Badwater, women and men became faster over the years. The running speed increased from 7.9 ± 0.7 to 8.7 ± 0.6 km/h (p < 0.01) in men and from 5.4 ± 1.1 to 6.6 ± 0.5 km/h (p < 0.01) in women. The sex difference in running speed remained unchanged at 19.8% ± 4.8% (p > 0.05). In Spartathlon, the running speed was stable over time at 10.8 ± 0.7 km/h for men and 8.7 ± 0.5 km/h for women (p > 0.05). The sex difference remained unchanged at 19.6% ± 2.5% (p > 0.05). Conclusions: These results suggest that for both Badwater and Spartathlon, (a) female participation increased, (b) the fastest finishers were approximately 40 to 45 years, and (c) the sex difference was at approximately 20%. Women will not outrun men in both Badwater and Spartathlon races. Master ultramarathoners can achieve a high level of performance in ultramarathons greater than 200 km under extreme conditions.

A report on the first conference on physiological and physical employment standards, Canberra, Australia November 27 to 28, 2012

Gemma Milligan — 2013-05-01T00:00:00Z

This is a report of the First Conference on Physiological and Physical Employment Standards. This was the first conference of its kind, attended by scientists, physicians, occupational medics, high-ranking politicians and military personal from ten nations.

Career perspective: Paolo Cerretelli

Paolo Cerretelli — 2013-04-25T00:00:00Z

This article is an autobiographical account of my career as a human physiologist. I have spent 55 years traversing mountains, continents, seas, and skies, carrying out research in the laboratories of several international institutions as well as in the field. My scientific roots, approach to the mountains and altitude populations, both in Europe and in Asia, together with an account of my experimental studies at altitude, including extreme conditions, shall be presented together with pertinent occasional reflections of a personal nature.

Sex difference in Double Iron ultra-triathlon performance

Katrin Sigg — 2013-04-01T00:00:00Z

Background: The present study examined the sex difference in swimming (7.8 km), cycling (360 km), running (84 km), and overall race times for Double Iron ultra-triathletes. Methods: Sex differences in split times and overall race times of 1,591 men and 155 women finishing a Double Iron ultra-triathlon between 1985 and 2012 were analyzed. Results: The annual number of finishes increased linearly for women and exponentially for men. Men achieved race times of 1,716 ± 243 min compared to 1,834 ± 261 min for women and were 118 ± 18 min (6.9%) faster (p < 0.01). Men finished swimming within 156 ± 63 min compared to women with 163 ± 31 min and were 8 ± 32 min (5.1 ± 5.0%) faster (p < 0.01). For cycling, men (852 ± 196 min) were 71 ± 70 min (8.3 ± 3.5%) faster than women (923 ± 126 min) (p < 0.01). Men completed the run split within 710 ± 145 min compared to 739 ± 150 min for women and were 30 ± 5 min (4.2 ± 3.4%) faster (p = 0.03). The annual three fastest men improved race time from 1,650 ± 114 min in 1985 to 1,339 ± 33 min in 2012 (p < 0.01). Overall race time for women remained unchanged at 1,593 ± 173 min with an unchanged sex difference of 27.1 ± 8.6%. In swimming, the split times for the annual three fastest women (148 ± 14 min) and men (127 ± 20 min) remained unchanged with an unchanged sex difference of 26.8 ± 13.5%. In cycling, the annual three fastest men improved the split time from 826 ± 60 min to 666 ± 18 min (p = 0.02). For women, the split time in cycling remained unchanged at 844 ± 54 min with an unchanged sex difference of 25.2 ± 7.3%. In running, the annual fastest three men improved split times from 649 ± 77 min to 532 ± 16 min (p < 0.01). For women, however, the split times remained unchanged at 657 ± 70 min with a stable sex difference of 32.4 ± 12.5%. Conclusions: To summarize, the present findings showed that men were faster than women in Double Iron ultra-triathlon, men improved overall race times, cycling and running split times, and the sex difference remained unchanged across years for overall race time and split times. The sex differences for overall race times and split times were higher than reported for Ironman triathlon.

A comparison between the 2010 and 2005 basic life support guidelines during simulated hypogravity and microgravity

Thais Russomano — 2013-04-01T00:00:00Z

Background: Current 2010 terrestrial (1Gz) CPR guidelines have been advocated by space agencies for hypogravity and microgravity environments, but may not be feasible. The aims of this study were to (1) evaluate rescuer performance over 1.5 min of external chest compressions (ECCs) during simulated Martian hypogravity (0.38Gz) and microgravity (μG) in relation to 1Gz and rest baseline and (2) compare the physiological costs of conducting ECCs in accordance with the 2010 and 2005 CPR guidelines. Methods: Thirty healthy male volunteers, ranging from 17 to 30 years, performed four sets of 30 ECCs for 1.5 min using the 2010 and 2005 ECC guidelines during 1Gz, 0.38Gz and μG simulations (Evetts-Russomano (ER) method), achieved by the use of a body suspension device. ECC depth and rate, range of elbow flexion, post-ECC heart rate (HR), minute ventilation (V E), peak oxygen consumption (VO2peak) and rate of perceived exertion (RPE) were measured. Results: All volunteers completed the study. Mean ECC rate was achieved for all gravitational conditions, but true depth during simulated microgravity was not sufficient for the 2005 (28.5 ± 7.0 mm) and 2010 (32.9 ± 8.7 mm) guidelines, even with a mean range of elbow flexion of 15°. HR, V E and VO2peak increased to an average of 136 ± 22 bpm, 37.5 ± 10.3 L·min−1, 20.5 ± 7.6 mL·kg−1·min−1 for 0.38Gz and 161 ± 19 bpm, 58.1 ± 15.0 L·min−1, 24.1 ± 5.6 mL·kg−1·min−1 for μG from a baseline of 84 ± 15 bpm, 11.4 ± 5.9 L·min−1, 3.2 ± 1.1 mL·kg−1·min-1, respectively. RPE was the only variable to increase with the 2010 guidelines. Conclusion: No additional physiological cost using the 2010 basic life support (BLS) guidelines was needed for healthy males performing ECCs for 1.5 min, independent of gravitational environment. This cost, however, increased for each condition tested when the two guidelines were compared. Effective ECCs were not achievable for both guidelines in simulated μG using the ER BLS method. This suggests that future implementation of an ER BLS in a simulated μG instruction programme as well as upper arm strength training is required to perform effective BLS in space.

Patent foramen ovale and scuba diving: a practical guide for physicians on when to refer for screening

Oliver Sykes — 2013-04-01T00:00:00Z

Divers are taught some basic physiology during their training. There is therefore some underlying knowledge and understandable concern in the diving community about the presence of a patent foramen ovale (PFO) as a cause of decompression illness (DCI). There is an agreement that PFO screening should not be done routinely on all divers; however, when to screen selected divers is not clear. We present the basic physiology and current existing guidelines for doctors, advice on the management and identify which groups of divers should be referred for consideration of PFO screening. Venous bubbles after diving and right to left shunts are common, but DCI is rare. Why this is the case is not clear, but the divers look to doctors for guidance on PFO screening and closure; both of which are not without risks. Ideally, we should advise and apply guidelines that are consistent and based on best available evidence. We hope this guideline and flow chart helps address these issues with regard to PFOs and diving.

Integrative physiology and systems biology: reductionism, emergence and causality

Michael P Grocott — 2013-03-22T00:00:00Z

No description available

Applying systems biology methods to the study of human physiology in extreme environments

Lindsay Edwards — 2013-03-22T00:00:00Z

Systems biology is defined in this review as ‘an iterative process of computational model building and experimental model revision with the aim of understanding or simulating complex biological systems’. We propose that, in practice, systems biology rests on three pillars: computation, the omics disciplines and repeated experimental perturbation of the system of interest. The number of ethical and physiologically relevant perturbations that can be used in experiments on healthy humans is extremely limited and principally comprises exercise, nutrition, infusions (e.g. Intralipid), some drugs and altered environment. Thus, we argue that systems biology and environmental physiology are natural symbionts for those interested in a system-level understanding of human biology. However, despite excellent progress in high-altitude genetics and several proteomics studies, systems biology research into human adaptation to extreme environments is in its infancy. A brief description and overview of systems biology in its current guise is given, followed by a mini review of computational methods used for modelling biological systems. Special attention is given to high-altitude research, metabolic network reconstruction and constraint-based modelling.

Minute ventilation and heart rate relationship for estimation of the ventilatory compensation point at high altitude: a pilot study

Gabriele Valli — 2013-03-01T00:00:00Z

Background: The ventilatory compensation point (VCP) is an exercise threshold which has been used in the design of training programs in sports medicine and rehabilitation. We recently demonstrated that changes in the slope of the minute ventilation to heart rate relationship ( Δ V ˙ E / Δ HR ) can be utilized for estimation of the VCP during incremental exercise at sea level (SL). We hypothesized that in hypoxic conditions, such as high altitude (HA), VCP can be also reliably estimated by Δ V ˙ E / Δ HR . Methods: At SL and on immediate ascent to HA (5,050 m), six healthy subjects (42 ± 14 SD years) performed a maximal incremental exercise test on a cycle ergometer; O2 uptake ( V ˙ O 2 ), CO2 output ( V ˙ CO 2 ), V ˙ E , and HR were measured breath-by-breath. The Δ V ˙ E / Δ HR method for VCP estimation was compared to the standard method using the ventilatory equivalent for CO2 ( V ˙ E / V ˙ C O 2 ) and end-tidal PCO2 (PETCO2). The Δ V ˙ E / Δ HR slope values below (S1) and above (S2) VCP were computed by linear regression analysis. Results: A significant difference between S1 and S2 was observed, at SL and HA, for both the Δ V ˙ E / Δ HR and V ˙ E / V ˙ CO 2 methods for VCP estimation. A good agreement between the two methods ( Δ V ˙ E / Δ HR vs. V ˙ E / V ˙ CO 2 ) was found for both environmental conditions; the mean difference ± 2 SD of V ˙ O 2 at VCP (VCP- V ˙ O 2 ) was −22 ± 112 ml/min at SL and 39 ± 81 ml/min at HA. The VCP- V ˙ O 2 was significantly lower at HA compared to SL; in addition, S1 and S2 mean values were significantly higher at HA compared to SL. Conclusion: At HA, VCP may be reliably estimated by the Δ V ˙ E / Δ HR method.