Martin Faulhaber

Interval hypoxic training improves autonomic cardiovascular and respiratory control in patients with mild chronic obstructive pulmonary disease

Objectives Chronic obstructive pulmonary disease (COPD) is associated with cardiac autonomic nervous system dysregulation. This study evaluates the effects of interval hypoxic training on cardiovascular and respiratory control in patients with mild COPD. Methods In 18 eucapnic normoxic mild COPD patients (age 51.7 ± 2.4 years, mean ± SEM), randomly assigned to either training or placebo group, and 14 age-matched healthy controls (47.7 ± 2.8 years), we monitored end-tidal carbon dioxide, airway flow, arterial oxygen saturation, electrocardiogram, and continuous noninvasive blood pressure at rest, during progressive hypercapnic hyperoxia and isocapnic hypoxia to compare baroreflex sensitivity to hypoxia and hypercapnia before and after 3 weeks of hypoxic training. In double-blind fashion, both groups received 15 sessions of passive intermittent hypoxia (training group) or normoxia (placebo group). For the hypoxia group, each session consisted of three to five hypoxic (15–12% oxygen) periods (3–5 min) with 3-min normoxic intervals. The placebo group inhaled normoxic air. Results Before training, COPD patients showed depressed baroreflex sensitivity, as compared with healthy individuals, without evident chemoreflex abnormalities. After training, in contrast to placebo group, the training group showed increased (P < 0.05) baroreflex sensitivity up to normal levels and selectively increased hypercapnic ventilatory response (P < 0.05), without changes in hypoxic ventilatory response. Conclusion Eucapnic normoxic mild COPD patients already showed signs of cardiovascular autonomic abnormalities at baseline, which normalized with hypoxic training. If confirmed in more severe patients, interval hypoxic training may be a therapeutic strategy to rebalance early autonomic dysfunction in COPD patients.

Hypoxia‐Related Altitude Illnesses

BACKGROUND Millions of tourists and climbers visit high altitudes annually. Many unsuspecting and otherwise healthy individuals may get sick when sojourning to these high regions. Acute mountain sickness represents the most common illness, which is usually benign but can rapidly progress to the more severe and potentially fatal forms of high-altitude cerebral edema and high-altitude pulmonary edema. METHODS Data were identified by searches of Medline (1965 to May 2012) and references from relevant articles and books. Studies, reviews, and books specifically pertaining to the epidemiology, prevention, and treatment of high-altitude illnesses in travelers were selected. RESULTS This review provides information on geographical aspects, physiology/pathophysiology, clinical features, risk factors, and the prevalence of high-altitude illnesses and also state-of-the art recommendations for prevention and treatment of such illnesses. CONCLUSION Given an increasing number of recreational activities at high and extreme altitudes, the general practitioner and specialist are in higher demand for medical recommendations regarding the prevention and treatment of altitude illness. Despite an ongoing scientific discussion and controversies about the pathophysiological causes of altitude illness, treatment and prevention recommendations are clearer with increased experience over the last two decades.

Intermittent hypoxia increases exercise tolerance in patients at risk for or with mild COPD

The effects of repeated short-term hypoxia on exercise tolerance in patients at risk for, or with mild COPD were investigated. Eighteen patients (10 males, 8 females; 33-72 years) were randomly assigned in a double-blind fashion to receive 15 sessions of intermittent hypoxia (FiO(2): 0.15-0.12) or normoxia within 3 weeks. Three weeks of intermittent hypoxia increased total haemoglobin mass (+4% vs. 0%, p<0.05), total exercise time (+9.7% vs. 0%, p<0.05) and the exercise time to the anaerobic threshold (+13% vs. -7.8%, p<0.05) compared to controls. Changes in the total exercise time were positively related to the changes in total haemoglobin mass (r=0.59, p<0.05) and changes in the time to the anaerobic threshold were positively related to the changes in the lung diffusion capacity for carbon monoxide (r=0.48, p<0.05). Intermittent hypoxia treatment may be a valuable addition to therapy designed to improve exercise tolerance in patients at risk for, or with mild COPD.

Hypoxia, Oxidative Stress and Fat

Metabolic disturbances in white adipose tissue in obese individuals contribute to the pathogenesis of insulin resistance and the development of type 2 diabetes mellitus. Impaired insulin action in adipocytes is associated with elevated lipolysis and increased free fatty acids leading to ectopic fat deposition in liver and skeletal muscle. Chronic adipose tissue hypoxia has been suggested to be part of pathomechanisms causing dysfunction of adipocytes. Hypoxia can provoke oxidative stress in human and animal adipocytes and reduce the production of beneficial adipokines, such as adiponectin. However, time-dose responses to hypoxia relativize the effects of hypoxic stress. Long-term exposure of fat cells to hypoxia can lead to the production of beneficial substances such as leptin. Knowledge of time-dose responses of hypoxia on white adipose tissue and the time course of generation of oxidative stress in adipocytes is still scarce. This paper reviews the potential links between adipose tissue hypoxia, oxidative stress, mitochondrial dysfunction, and low-grade inflammation caused by adipocyte hypertrophy, macrophage infiltration and production of inflammatory mediators.

Short-term supplementation with alpha-ketoglutaric acid and 5-hydroxymethylfurfural does not prevent the hypoxia induced decrease of exercise performance despite attenuation of oxidative stress.

Reactive oxygen species are thought to partly be responsible for the hypoxia induced performance decrease. The present study evaluated the effects of a broad based antioxidant supplementation or the combined intake of alpha-ketoglutaric acid (α-KG) and 5-hydroxymethylfurfural (5-HMF) on the performance decrease at altitude. 18 healthy, well-trained males (age: 25±3 years; height: 179±6 cm; weight: 76.4±6.8 kg) were randomly assigned in a double-blind fashion to a placebo group (PL), a α-KG and 5-HMF supplementation group (AO1) or a broad based antioxidant supplementation group (AO2). Participants performed 2 incremental exercise tests to exhaustion on a cycle ergometer; the first test under normoxia and the second under hypoxia conditions (simulated altitude, FiO2=13% ~ 4 300 m). Supplementation started 48 h before the hypoxia test. Maximal oxygen uptake, maximal power output, power output at the ventilatory and lactate threshold and the tissue oxygenation index (NIRS) were measured under both conditions. Oxidative stress markers were measured before the supplementation and after the hypoxia test. Under hypoxia conditions all performance parameters decreased in the range of 19-39% with no differences between groups. A significant change from normoxia to hypoxia (p<0.001) and between groups (p=0.038) were found for the tissue oxygenation index. Post hoc test revealed significant differences between the PL and both, the AO1 and the AO2 group. The oxidative stress parameter carbonyl protein changed from normoxia to hypoxia in all participants and 4-hydroxynonenal decreased in the AO1 group only. In conclusion the results suggest that short-term supplementation with an antioxidant does not prevent the performance decrease at altitude. However, positive effects on muscle oxygen extraction, as indicated by the tissue oxygenation index, might indicate that mitochondrial functioning was actually influenced by the supplementation.

Effects of intermittent hypoxia on running economy.

We investigated the effects of two 5-wk periods of intermittent hypoxia on running economy (RE). 11 male and female middle-distance runners were randomly assigned to the intermittent hypoxia group (IHG) or to the control group (CG). All athletes trained for a 13-wk period starting at pre-season until the competition season. The IHG spent additionally 2 h at rest on 3 days/wk for the first and the last 5 weeks in normobaric hypoxia (15-11% FiO2). RE, haematological parameters and body composition were determined at low altitude (600 m) at baseline, after the 5 (th), the 8 (th) and the 13 (th) week of training. RE, determined by the relative oxygen consumption during submaximal running, (-2.3+/-1.2 vs. -0.3+/-0.7 ml/min/kg, P<0.05) and total running time (+1.0+/-0.9 vs. +0.4+/-0.5 min, P<0.05) changed significantly between the IHG and CG only during the first 5-wk period. Haematological and cardiorespiratory changes indicate that the improved RE was associated with decreased cardiorespiratory costs and greater reliance on carbohydrate. Intermittent hypoxia did not affect RE during the second 5-wk period. These findings suggest that the effects of intermittent hypoxia on RE strongly depend on the training phase.

Normobaric Intermittent Hypoxia over 8 Months Does Not Reduce Body Weight and Metabolic Risk Factors - a Randomized, Single Blind, Placebo-Controlled Study in Normobaric Hypoxia and Normobaric Sham Hypoxia

Objective: Both a 1- to 4-week continuous or intermittent stay and moderate exercise in hypoxia versus normoxia can lead to weight loss. We examined the reproducibility and durability of added hypoxic exposure in a feasible health program of several months. Methods: 32 obese persons, randomly assigned to either a hypoxia (age 50.3 ± 10.3 years, BMI 37.9 ± 8.1 kg/m²) or a normoxia (age 52.4 ± 7.9 years, BMI 36.3 ± 4.0 kg/m²) group, completed 52 exercise sessions within 8 months. Participants exercised for 90 min (65-70% HRpeak) either at a simulated altitude of 3,500 m or in normoxia, and rested for further 90 min at 4,500 m or normoxia. Before, after 5 weeks, after 3 months, and after the intervention, body composition and exercise capacity were determined. Risk markers (e.g., blood pressure, cholesterol) were measured before, after 3 months, and after the intervention period. Results: Body weight, BMI, waist and hip circumference, Ppeak and BPsys improved over time (p < 0.05) but without group difference. Fat mass reductions correlated with HDL changes (r = -0.427; p < 0.05) in the entire group. Conclusion: Long-term, moderate intensity exercise and rest in hypoxia does not lead to higher reductions in body weight than normoxia alone. Therefore, for weight loss and metabolic markers hypoxic exposure does not add effects at least when stimuli (i.e., hypoxia dose, exercise intensity/duration) are unaltered throughout the intervention.

Intermittent hypoxia does not affect endurance performance at moderate altitude in well-trained athletes

Abstract In this study, we examined the effects of a pre-acclimatization programme on endurance performance at moderate altitude using a resting intermittent hypoxia protocol. The time-trial performance of 11 cyclists was determined at low altitude (600 m). Athletes were randomly assigned in a double-blind fashion to the hypoxia or the control group. The pre-acclimatization programme consisted of seven sessions each lasting 1 h in normobaric hypoxia (inspired fraction of oxygen of 12.5%, equivalent to approximately 4500 m) for the hypoxia group (n = 6) and in normoxia (inspired fraction of oxygen of 20.9%) for the control group (n = 5). The time-trials were repeated at moderate altitude (1970 m). Mean power output during the time-trial at moderate altitude was decreased in the hypoxia group (−0.26 ± 0.11 W · kg−1) and in the control group (−0.13 ± 0.04 W · kg−1) compared with at low altitude but did not differ between groups (P = 0.13). Our results suggest that the applied protocol of intermittent hypoxia had no positive effect on endurance performance at moderate altitude. Whether different intermittent hypoxia protocols are advantageous remains to be determined.

Kardiorespiratorische und metabolische Reaktionen beim Bergwandern und alpinen Skilauf

SummaryIn Austria, more than 10 million hikers and skiers annually visit moderate altitudes. Nevertheless, there is little information on the frequency of cardiovascular diseases in mountaineers and the exercise responses during physical activity in the mountains. The prevalence of cardiovascular diseases was determined by an inquiry of 527 mountain hikers and 785 alpine skiers. Two groups (n = 35) performed step tests at low altitude (600 m) and at high altitude (2000 m and 3500 m). Exercise responses to hiking and skiing were recorded in the subjects of the third group (n = 10). Hiking and skiing at moderate intensity evoked moderate cardiovascular and metabolic responses which are also well tolerated by persons with non-severe cardiovascular and respiratory diseases. Low fitness, increasing altitude and intensity increased exercise responses, thereby enhancing the probability of cardiovascular events. A high degree of fitness based on regular training decreases exercise responses and improves exercise tolerance.ZusammenfassungIn Österreich besuchen jährlich über 10 Millionen Wanderer und Skifahrer mittlere Höhenlagen. Dennoch existieren nur wenige Basisinformationen über die Häufigkeit von Herzkreislauferkrankungen sowie Belastungsreaktionen bei körperlicher Aktivität in den Bergen. Eine Stichprobe von insgesamt 527 Bergwanderern und 785 Skifahrern diente der Erhebung der Prävalenz von Herzkreislauferkrankungen. Zwei Gruppen (n = 35) führten einen Stufentest in Tallage (600 m) und anschließend in Höhenlage (2000 m und 3500 m) durch. Bei den Probanden der Gruppe 3 (n = 10) wurden Belastungsreaktionen beim Bergwandern und Skifahren aufgezeichnet. Bei moderater Intensität durchgeführtes Bergwandern und Skifahren bewirkte bei gesunden Personen mittleren und höheren Alters auch nur moderate kardiorespiratorische und metabolische Belastungsreaktionen, die auch von Menschen mit leichten Herzkreislauf- und Atemwegserkrankungen gut toleriert werden. Niedrige Fitness, zunehmende Höhe und Belastungsintensität bewirkten deutlich ausgeprägtere Belastungsreaktionen, was die Wahrscheinlichkeit von kardiopulmonalen Zwischenfällen anwachsen lässt. Ein ausreichend hoher Fitnessgrad durch regelmäßiges Training ist mit geringeren Belastungsreaktionen und dadurch gesteigerter Belastungstoleranz verbunden.

Factors Associated With the Ability to Estimate Actual Speeds in Recreational Alpine Skiers

OBJECTIVE To measure on-slope speeds of alpine skiers and to compare their ability to accurately estimate their actual speed with regard to measured speed, age, sex, skill level, helmet use, and risk-taking behavior. METHODS Skiing speeds of 416 adult skiers (62% men, 38% women) were measured with a radar speed gun. Skiers were interviewed about their age, sex, skiing ability, helmet use, and risk-taking behavior. Additionally, skiers had to estimate their measured speed as accurately as possible. The difference between estimated and measured speed was described as error of estimation (EE). RESULTS Mean measured speed (±SD) of all participants was 48.2 (±14.3) km/h. Pearson correlation coefficient between the actual speed and the estimated speed was 0.57 (P < .001) for all participants. Skiers underestimated their measured speed on average by 5.8 km/h or 8.1%. A multiple hierarchical linear regression analysis revealed that when skiing speed is increased by 1 km/h the EE significantly decreases by 0.5 km/h. Male sex, higher skill level, risky skiing behavior, and younger age groups showed a significantly better ability to estimate skiing speed, whereas ski helmet use did not. CONCLUSIONS Skiing speed, age, sex, skill level, and risk-taking behavior seem to influence the ability to estimate actual speeds in recreational alpine skiers.