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The purpose of this study was to investigate the resistance to breathing (RES) in heat and moisture exchanging devices (HME) intended for use during physical activity in the cold. RES was investigated for seventeen HMEs, including different types of filters. In addition, the influence of headwind on RES was tested using four representative HMEs. HMEs were mounted to the face of an artificial head manufactured from ABS plastic. The HMEs were connected to a mechanical lung simulator, which delivered standardised inspiratory and expiratory air flow rates (V·, L/s). The delta pressure (Δp, Pa) between ambient air and the air inside the HME was measured, whereupon RES was calculated. The results showed significant (p< 0.05) differences in RES between HMEs from different manufacturers, while the difference was smaller, and in some cases not significant (p> 0.05), between different models/filters within the same brand. The results also showed that RES was highly influenced by different ventilations and headwind conditions. RES increased with increased V·and, when a headwind was introduced, RES decreased during inspiration and increased during expiration. Calculations showed that the oxygen and energy cost for breathing through an HME was very small for most of the tested models. The effect of HME dead space on pulmonary gas fractions depends on the tidal volume. At large tidal volumes and ventilations, the effect of HMEs on pulmonary gas fractions becomes relatively small.

The aim of this study was to investigate the effects on pulmonary ventilation and oxygen uptake (V.O2) in athletes with a very high maximal oxygen uptake (V.O2max) and corresponding high ventilation capacity when using a modern metabolic system with relatively high resistance to breathing (HIGHRES), compared to a traditional system with low resistance to breathing (LOWRES). Four rowers and three cross-country skiers (without asthma), competing at a high international level, performed in experimental conditions with LOWRESand HIGHRESusing a rowing ergometer and roller skis on a treadmill. The results showed that V.O2, blood lactate, heart rate and respiratory exchange ratio were not different between the LOWRESand HIGHREStest conditions during both submaximal and maximal exercise. Also, the athlete’s time to exhaustion (treadmill) and mean power (rowing ergometer) from maximal tests were no different between the two conditions. However, ventilation and expiratory O2and CO2concentrations were different for both submaximal and maximal exercise. Thus, the authors have concluded that the differences in resistance to breathing of metabolic systems influence elite endurance athletes V.Eat low to very high workloads, thus affecting the expired gas fractions, but not the submaximal V.O2, V.O2maxand performance in a laboratory setting at sea level.

The aim of this project was to develop a wind tunnel that enables the study of human performance during various types of sports and physical activities by examining the influence of aerodynamic drag, precipitation, frictional forces and gravitational forces on uphill and downhill travel on a moving substrate. An overall design for a wind tunnel and working section containing a large treadmill was drafted, followed by computational fluid dynamics simulations of flow conditions to assess the design’s feasibility and select from different geometries prior to its construction. The flow conditions in the completed wind tunnel were validated using different flows, speeds and treadmill inclinations. Pilot experiments were carried out using a cross-country skier to investigate the effect of aerodynamic drag on oxygen uptake during double poling and the maximal achieved speed when rolling on a declined treadmill. The purpose was to validate the usefulness of the tunnel. The results showed that flow conditions are acceptable for experiments even in worst-case scenarios with maximal inclined and declined treadmill. Results also showed that aerodynamic drag has a significant impact on the skier’s energy expenditure.

The purpose of this study was to investigate the resistance to breathing in metabolic systems used for the distribution and measurement of pulmonary gas exchange. A mechanical lung simulator was used to standardize selected air flow rates (V·, L/s). The delta pressure (Δp, Pa) between the ambient air and the air inside the equipment was measured in the breathing valve’s mouthpiece adapter for four metabolic systems and four types of breathing valves. Resistance for the inspiratory and expiratory sides was calculated as RES = (Δp/V·) Pa/L/s. The results for resistance showed significant (p< 0.05) between-group variance among the tested metabolic systems, breathing valves, and between most of the completed V·. The lowest resistance among the metabolic systems was found for a Douglas Bag system which had approximately half of the resistance compared to the automated metabolic systems. The automated systems were found to have higher resistance even at low V·in comparison with previous findings and recommendations. For the hardware components, the highest resistance was found for the breathing valves, while the lowest resistance was found for the hoses. The results showed that resistance in metabolic systems can be minimized through conscious choices of system design and hardware components.

Background: Astronauts are required to perform both resistance and aerobic exercise while in orbit. This study assessed the aerobic energy yield and related physiological measurements using a nongravity de-pendent flywheel device designed for both resistance and aerobic exer-cise (RAD) in space. Methods: Eight physically active men and women performed all-out rowing on the RAD. For comparison, exercise was also carried out employing a commercially available rowing ergometer (C2). Results: Peak oxygen uptake during exercise using RAD and C2 averaged 3.11 ± 0.49 and 3.18 ± 0.50 L · min-1 respectively. Similarly, peak plasma lactate concentration (9.6 vs. 11.2 mmol · L-1), heart rate (183 vs. 184 bpm), and rate of perceived exertion (15.8 vs. 16.0) were comparable across exercise using the two devices. Discussion: Collectively, the results suggest that this novel exercise modality offers cardiovascular and metabolic responses, and thus aerobic exercise stimulus that is equally effective as that evoked by established technol-ogy for indoor rowing. Given the need for physiologically sound and highly effective exercise countermeasures that features small mass and envelope, and allows for resistance and aerobic exercise in a single apparatus, we believe this novel hardware should be considered for use in space. [ABSTRACT FROM AUTHOR]