V_ESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia

This study compared the ventilation response to an incremental ergometer exercise at two altitudes: 633 mmHg (resident altitude = 1,600 m) and following acute decompression to 455 mmHg (≈4,350 m altitude) in eight male cyclists and runners. At 455 mmHg, the VESTPD at RER EBTPS was higher because of higher breathing frequency; at VO2max, both VESTPD and VEBTPS were not significantly different. As percent of VO2max, the VEBTPS was nearly identical and VESTPD was 30% lower throughout the exercise at 455 mmHg. The lower VESTPD at lower pressure differs from two classical studies of acclimatized subjects (Silver Hut and OEII), where VESTPD at submaximal workloads was maintained or increased above that at sea level. The lower VESTPD at 455 mmHg in unacclimatized subjects at submaximal workloads results from acute respiratory alkalosis due to the initial fall in HbO2 (≈0.17 pHa units), reduction in PACO2 (≈5 mmHg) and higher PAO2 throughout the exercise, which are partially pre-established during acclimatization. Regression equations from these studies predict VESTPD from VO2 and PB in unacclimatized and acclimatized subjects. The attainment of ventilatory acclimatization to altitude can be estimated from the measured vs. predicted difference in VESTPD at low workloads after arrival at altitude

The effect of aging on the autophagic and heat shock response in human peripheral blood mononuclear cells

Autophagy is a lysosome degradation pathway through which damaged organelles and macromolecules are degraded within the cell. A decrease in activity of the autophagic process has been linked to several age-associated pathologies, including triglyceride accumulation, mitochondrial dysfunction, muscle degeneration, and cardiac malfunction. Here, we examined the differences in the autophagic response using autophagy-inducer rapamycin (Rapa) in peripheral blood mononuclear cells (PBMCs) from young (21.8 ± 1.9 years) and old (64.0 ± 3.7 years) individuals. Furthermore, we tested the interplay between the heat shock response and autophagy systems. Our results showed a significant increase in LC3-II protein expression in response to Rapa treatment in young but not in old individuals. This was associated with a decreased response in MAP1LC3B mRNA levels, but not SQSTM1/p62. Furthermore, HSPA1A mRNA was upregulated only in young individuals, despite no differences in HSP70 protein expression. The combined findings suggest a suppressed autophagic response following Rapa treatment in older individuals

Minute ventilation of cyclists, car and bus passengers: an experimental study

<p>Abstract</p> <p>Background</p> <p>Differences in minute ventilation between cyclists, pedestrians and other commuters influence inhaled doses of air pollution. This study estimates minute ventilation of cyclists, car and bus passengers, as part of a study on health effects of commuters' exposure to air pollutants.</p> <p>Methods</p> <p>Thirty-four participants performed a submaximal test on a bicycle ergometer, during which heart rate and minute ventilation were measured simultaneously at increasing cycling intensity. Individual regression equations were calculated between heart rate and the natural log of minute ventilation. Heart rates were recorded during 280 two hour trips by bicycle, bus and car and were calculated into minute ventilation levels using the individual regression coefficients.</p> <p>Results</p> <p>Minute ventilation during bicycle rides were on average 2.1 times higher than in the car (individual range from 1.3 to 5.3) and 2.0 times higher than in the bus (individual range from 1.3 to 5.1). The ratio of minute ventilation of cycling compared to travelling by bus or car was higher in women than in men. Substantial differences in regression equations were found between individuals. The use of individual regression equations instead of average regression equations resulted in substantially better predictions of individual minute ventilations.</p> <p>Conclusion</p> <p>The comparability of the gender-specific overall regression equations linking heart rate and minute ventilation with one previous American study, supports that for studies on the group level overall equations can be used. For estimating individual doses, the use of individual regression coefficients provides more precise data. Minute ventilation levels of cyclists are on average two times higher than of bus and car passengers, consistent with the ratio found in one small previous study of young adults. The study illustrates the importance of inclusion of minute ventilation data in comparing air pollution doses between different modes of transport.</p

A comparison of body composition assessment methods in climbers: Which is better?

Objective To compare body composition estimations of field estimation methods: Durnin & Womersley anthropometry (DW-ANT), bioelectrical impedance analysis (BIA) and Deborah-Kerr anthropometry (DK-ANT) against dual-energy X-ray absorptiometry (DXA) in a male Chilean sport climbing sample. Methods 30 adult male climbers of different performance levels participated in the study. A DXA scan (Lunar Prodigy (R)) was used to determine fat mass, lean mass and total bone mineral content (BMC). Total muscle mass (MM, kg) was estimated through a validated prediction model. DW-ANT and BIA ("non-athletes" and "athletes" equations) were used to determinate fat mass percentage (FM %), while DK-ANT was utilized to estimate MM and BMC. Results A significant (p<0.01) inter-method difference was observed for all methods analyzed. When compared to DXA, DW-ANT and BIA underestimated FM% and DK-ANT overestimated MM and BMC (All p< 0.01). The inter-method differences was lower for DW-ANT. Discussion We found that body composition estimation in climbers is highly method dependent. If DXA is not available, DW-ANT for FM% has a lower bias of estimation than BIA in young male Chilean climbers. For MM and BMC, further studies are needed to compare and estimate the DK-ANT bias level. For both methods, correction equations for specific climbing population should be considered

Design and performance of personal cooling garments based on three-layer laminates

Personal cooling systems are mainly based on cold air or liquids circulating through a tubing system. They are weighty, bulky and depend on an external power source. In contrast, the laminate-based technology presented here offers new flexible and light weight cooling garments integrated into textiles. It is based on a three-layer composite assembled from two waterproof, but water vapor permeable membranes and a hydrophilic fabric in between. Water absorbed in the fabric will be evaporated by the body temperature resulting in cooling energy. The laminate's high adaptiveness makes it possible to produce cooling garments even for difficult anatomic topologies. The determined cooling energy of the laminate depends mainly on the environmental conditions (temperature, relative humidity, wind): heat flux at standard climatic conditions (20 degrees C, 65% R.H., wind 5 km/h) has measured 423.2 +/- 52.6 W/m(2), water vapor transmission resistance, R (et), 10.83 +/- 0.38 m(2) Pa/W and thermal resistance, R (ct), 0.010 +/- 0.002 m(2) K/W. Thermal conductivity, k, changed from 0.048 +/- 0.003 (dry) to 0.244 +/- 0.018 W/m K (water added). The maximum fall in skin temperature, Delta T (max), under the laminate was 5.7 +/- 1.2 degrees C, taken from a 12 subject study with a thigh cooling garment during treadmill walking (23 degrees C, 50% R.H., no wind) and a significant linear correlation (R = 0.85, P = 0.01) between body mass index and time to reach 67% of Delta T (max) could be determined

Estimation of hand and wrist muscle capacities in rock climbers

International audiencePurpose: This study investigated the hand and wrist muscle capacities among expert rock climbers and compared them with those of non-climbers. The objective was to identify the adaptations resulting from several years of climbing practice.Methods: Twelve climbers (nine males and three females) and 13 non-climber males participated in this study. Each subject performed a set of maximal voluntary contractions about the wrist and the metacarpo-phalengeal joints during which net joint moments and electromyographic activities were recorded. From this data set, the muscle capacities of the five main muscle groups of the hand (wrist flexors, wrist extensors, finger flexors, finger extensors and intrinsic muscles) were estimated using a biomechanical model. This process consisted in adjusting the physiological crosssectional area (PCSA) and the maximal muscle stress value from an initial generic model.Results: Results obtained from the model provided several new pieces of information compared to the analysis of only the net joint moments. Particularly, the capacities of the climbers were 37.1 % higher for finger flexors compared to non-climbers and were similar for finger extensor and for the other muscle groups. Climbers thus presented a greater imbalance between flexor and extensor capacities which suggests a potential risk of pathologies.Conclusions: The practice of climbing not only increased the strength of climbers but also resulted in specific adaptations among hand muscles. The proposed method and the obtained data could be re-used to optimize the training programs as well as the rehabilitation processes followinghand pathologies