Asthma in medium altitude--exercise-induced bronchoconstriction in hypobaric environment in subjects with asthma.

BACKGROUND: Hypoxic gas inhalation has been reported to enhance airway responsiveness and results in bronchoconstriction in animal models and in humans with asthma. However, the data have so far been conflicting. The aim of the present study was to examine the effect of reduced barometric pressure on exercise-induced bronchoconstriction (EIB) in subjects with asthma. METHODS: Twenty subjects (10-45 years old, male symbol/female symbol = 13/7) with asthma (at least 10% reduction in forced expiratory volume in 1-second postexercise) participated in exercise testing in barometric pressure corresponding to altitudes of 200 (normobaric) and 2500 (hypobaric) m above sea level in random order on separate days. Lung function was measured before and after exercise, as well as after inhalation of salbutamol. Heart rate, oxygen uptake (), arterial oxygen saturation (S(p)O(2)), respiratory gas exchange ratio (RER) and minute ventilation () were measured during exercise. RESULTS: There was no difference in lung function after exercise. The and HR(peak) during exercise did not differ. The RER(peak) was higher (P = 0.04) in hypobaric environment. The decreased 10.1% (7.2-13.0) [mean (95% confidence intervals)] (P < 0.001) from normobaric to hypobaric environment. At the same time, S(p)O(2) at decreased from 94.4 (92.2-96.6) to 85.6% (82.8-88.4) (P < 0.001). CONCLUSIONS: A barometric pressure corresponding to altitude of 2500 m did not increase EIB in subjects with asthma. The reduction in is most probably due to the lower S(p)O(2) in hypobaric environment.

Stress reactivity to and recovery from a standardised exercise bout: a study of 31 runners practising relaxation techniques.

OBJECTIVE: To compare the efficacy in runners of two relaxation techniques with regard to exercise reactivity and recovery after exercise. METHODS: Thirty one adult male runners were studied prospectively for six months in three groups practising either meditation (n = 11) or autogenic training (n = 11) or serving as controls (n = 10). Before and after the six months relaxation intervention, indicators of reactivity to exercise and metabolism after exercise (blood lactate concentration, heart rate (HR), and oxygen consumption (VO2)), were tested immediately after and 10 minutes after exercise. Resting HR was also assessed weekly at home during the trial. State anxiety was measured before and after the intervention. RESULTS: After the relaxation training, blood lactate concentration after exercise was significantly (p<0.01) decreased in the meditation group compared with the control group. No difference was observed in lactate responses between the autogenic training group and the control group. There were no significant differences among the groups with regard to HR, VO2, or levels of anxiety. CONCLUSION: Meditation training may reduce the lactate response to a standardised exercise bout.

A comparison of VO2(peak) between patients with congenital heart disease and healthy subjects, all aged 8-17 years.

The peak oxygen uptake (VO2(peak)) of 196 healthy children and adolescents aged 8-16 years, and 187 children and adolescents (in the same age range) with congenital heart disease (CHD), was measured using a graded treadmill test (Oslo-protocol). The healthy population was tested to assess the reference values that were to be used in the interpretation of the results obtained from patients with CHD. The results revealed that patients with CHD exhibited lower VO2(peak) values, with declining values for boys after the age of 12-13 years. When separated into different diagnostic groups, on average, patients with a chronic pressure overload of the left ventricle and patients with tetralogy of Fallot have lower VO2(peak) values, but make approximately the same progress with age as healthy subjects. Patients with transposition of the great arteries, however, displayed a marked decline in VO2(peak) after the age of 12-13 years. Whether exercise testing should be included in routine follow-up in patients with CHD, especially those between the ages of 10 and 16 years, when the condition of some patients deteriorates, requires special attention.

Aerobic endurance testing of children and adolescents--a comparison of two treadmill-protocols.

Fifty-eight children and adolescents of both sexes, aged 8-16, were tested on a treadmill using two different protocols. The well-known Bruce-protocol has the disadvantages of steep incline and large increments at each step. A new protocol (Oslo-protocol) with less incline and smaller increments was compared to the Bruce-protocol. The results from the two protocols showed no differences with regard to peak oxygen uptake (VO2peak) or peak heart rate (HRpeak). However, the respiratory exchange ratio (R) and blood lactate concentration [La-] showed higher values when the Bruce-protocol was used. The study also indicated that the often used criteria of HRpeak, R and achievement of a plateau in VO2 to estimate VO2peak, were not reliable indicators in either protocol. When time to exhaustion was used as an estimation of aerobic endurance level, the Oslo-protocol discriminated better than the Bruce-protocol. As a conclusion, the results indicate that none of the criteria may be used as a reliable indicator of having achieved VO2peak. An experienced testleader may be essential to define when VO2peak has been reached in children. On the basis of the results from the current study, the Oslo-protocol seems suitable as a test-protocol when testing children and adolescents for VO2peak.

[Aerobic capacity in children and adolescents--Nordic results over the past 45 years]. / Aerob kapasitet hos barn og unge--nordiske resultater gjennom 45 år.

The aim of this study was to reveal whether today's children and adolescents have lower aerobic capacity compared with earlier studies. Aerobic capacity may be defined as the highest amount of oxygen a subject is able to consume per unit of time. Peak oxygen uptake (VO2peak) is often used as a measure of aerobic capacity in children. VO2peak in 196 healthy children and adolescents of both sexes, aged 8-16 years, was measured on a graded treadmill test. The mean results of VO2peak (l.min-1) showed only small differences compared with previous studies in Scandinavia. There was, however, greater dispersion in the present study when the VO2peak-values were corrected for weight (ml.kg-1.min-1) than in the earlier studies. When compared to other countries in Europe, Norwegian subjects achieved higher values. The reason may be due to either genetic differences or to a higher level of physical activity among the Norwegian subjects.

[A protocol for testing aerobic capacity in children and adolescents with congenital heart defects]. / Protokoll for testing av aerob kapasitet hos barn og unge med medfødte hjertefeil.

Testing aerobic capacity is compulsory when diagnosing the severity of heart failure in adults. Up until now, physical testing of children and adolescents with congenital heart disease has only been done sporadically. An ergometer bicycle is the most extensively used method for testing adults, but it is usually designed for adults and can seldom be adjusted properly for small children. Treadmill is the most extensively used ergometer for testing children; it does not require any adjustment and allows a more dynamic pattern of movement where more muscle mass is in use. A test-protocol for children should allow for warming-up, should not have too steep an incline and there should only be small increments between each stage. Likewise the increments between each stage should become smaller as the workload increases. This is especially relevant for children and adolescents with congenital heart diseases, since they usually have less muscle mass than healthy subjects. Oxygen uptake should be measured during the test together with EKG, blood pressure and oxygen saturation. In this way, valuable information on the patients' aerobic capacity is gained.

The effect of inhaled salbutamol and salmeterol on lung function and endurance performance in healthy well-trained athletes.

The present randomized, double-blind placebo-controlled study aimed at investigating the possible improvement in endurance performance caused by inhaled salmeterol (long-acting beta 2-agonist) and salbutamol (short-acting) compared to placebo in 18 healthy well-trained athletes, aged 17-30 years old. Lung function (flow-volume loops) was measured before and after each inhaled study drug and after run to exhaustion. After inhalation of study drug and 10 min warm-up, anaerobic threshold was measured; thereafter maximum oxygen uptake, peak ventilation and running time until exhaustion during a brief graded exercise were measured. No significant differences were found for ventilation, oxygen uptake or heart rate at anaerobic threshold or at maximum performance between placebo and the beta 2-agonists. Lung function increased significantly after exercise, but without differences between the beta 2-agonists and placebo. Running time till exhaustion was significantly reduced after both the long- and the short-acting beta 2-agonist compared to the placebo.

Meditation: a modulator of the immune response to physical stress? A brief report.

OBJECTIVE: To test the hypothesis that stress reducing techniques such as meditation alter immune responses after strenous physical stress. METHODS: The hypothesis was tested by studying six meditating and six non-meditating male runners in a concurrent, controlled design. After a period of six months with meditation for the experimental group, blood samples were taken immediately before and after a maximum oxygen uptake test (VO2max). RESULTS: The increase in CD8+ T cells after VO2max was significantly less in the meditation group than in the control group (P = 0.04). The amount of CD2+ cells doubled after VO2max, mainly because of a rise in the CD8+ fraction. CONCLUSIONS: Meditation may modify the suppressive influence of strenous physical stress on the immune system.

[High altitude training]. / Høydetrening.

The physiological rationale for altitude training is discussed in the article. Acclimatisation to high altitude is accompanied by increases in haematocrit and haemoglobin concentrations, primarily due to a reduction in plasma volume but also to increased erythropoiesis as a result of enhanced erythropoietin release. Owing to the reduction of training load during acclimatisation, maximal aerobic capacity is not necessarily enhanced after high altitude training. However, the increase in the blood lactate concentration during standardised submaximal work has been shown to be significantly reduced--reflecting improved ability to exercise at higher submaximal workloads, as compared with previous ability at lower altitudes. An increase in buffer capacity may be responsible. The importance of a reduced training load and individualised control of training intensity during the acclimatisation period is emphasised. This control takes the form of regular heart rate monitoring and comparison of the blood lactate concentration during training sessions with the individual's pre-established 'lactate profile'. The Norwegian Altitude training project, including the various routines, procedures and problems involved in three successive sojourns at moderate altitudes, is briefly discussed. Finally, a practical approach to altitude training is presented--dealing with training control, iron demand, nutritional advice, fluid intake and recovery. Only top athletes should be selected for training at high altitudes.

Rate of accumulation of blood lactate during graded exercise as a predictor of 'anaerobic threshold'.

The subject group comprised 35 endurance-trained males: 11 young adults, 11 seniors and a control group of 13 young adults. A graded submaximal exercise test on a treadmill was performed by 22 of the subjects. The exponential function [La-] = a.ebx + c (where x = running velocity) showed a high degree of correlation with the experimental results (mean r = 0.997) and had randomly distributed residuals. Twenty-two subjects performed a series of running sessions at constant speed to establish the highest working intensities that could be endured without an increase in blood lactate (BLa) - the maximal steady-state workload (MSSW). The observed velocities of MSSW were related to the BLa vs velocity curves from the graded test. The graded submaximal exercise tests yielded mean derivatives from the BLa vs velocity relationship curves equal to 0.089 and 0.083 mM per m.min-1 for the young and senior groups, respectively. The derivatives had moderate inter-individual variations. In reversing the procedure, MSSW was estimated for all of the subjects using a common slope of 0.086. Only small individual variations were found between observed and estimated MSSW. The mean BLa value f (x), calculated using exponential functions where x = individual observed MSSW, was 3.0 mM. Thus, for endurance-trained athletes, a BLa accumulation rate of 0.086 mM per m.min-1 or, alternatively, a fixed BLa concentration of 3 mM, is recommended as a predictor of MSSW when analysing the BLa-velocity profiles from a graded submaximal test.

L-tryptophan supplementation does not improve running performance.

In 1988 Segura and Ventura (14) reported that 1.2 g of L-Tryptophan (L-TRY) supplementation increased total exercise time by 49.4% when the subjects were running at 80% of maximal oxygen uptake (VO2max). In human performance research, acute improvements of that category are rather uncommon. Both for this reason and because ingestion of purified L-TRY may have adverse effects, it seemed pertinent to repeat the investigation of Segura and Ventura. Forty-nine well-trained male runners, aged 18-44, with an average maximal aerobic power of 66 (57-78) ml.kg-1.min-1, participated in a randomized double blind placebo (P) study. Each subject underwent four trials on the treadmill. The first two served as learning experience, including measurement of VO2max and anaerobic threshold. During the last two trials the subjects ran until exhaustion at a speed corresponding to 100% of their VO2max-first an initial trial and then after receiving a total of 1.2 g L-TRY or P over a 24 hour period prior to the run. No significant difference between the improvements in the L-TRY and P group could be demonstrated. It is concluded that oral L-TRY supplementation does not enhance running performance.

Physiological effects of altitude training on elite male cross-country skiers.

Seven elite male cross-country skiers trained for 3 weeks at an altitude of 1900 m. Haemoglobin concentration ([Hb]), haematocrit (Hct) (obtained from venous blood), maximal oxygen uptake (VO2 max) and energy expenditure during a standard submaximal workload were measured before and after training at altitude, and 1 year later while training at sea level (control). Both [Hb] and Hct increased significantly, and the skiers with the lowest initial [Hb] and Hct experienced the largest increases during training at altitude. The increase in blood lactate (BLa) concentration (using haemolysed capillary blood) during a standard submaximal exercise test was significantly lower after training at altitude than before it or 1 year later (control). A significant correlation was found between the magnitude of increase in [Hb] and Hct and the difference in the lactate response to the standard submaximal workload pre- and post-altitude training. Although VO2 max remained unchanged, lower BLa concentration during the submaximal test probably reflects an improved ability to exercise at higher submaximal workloads shortly after training at altitude compared with pre-altitude training. It is suggested that subjects with low initial [Hb] and Hct improve their aerobic performance capacity most during altitude training.

Development of maximal oxygen uptake in young elite male cross-country skiers: a longitudinal study.

The aim of this study was to investigate the effects of extensive endurance training (15-25 h per week) on the development of maximal oxygen uptake (VO2 max) in boys from puberty. Maximal oxygen uptake was measured a number of times each year from the age of puberty and for the next 6-9 years in seven young male elite cross-country skiers. Mean VO2 max was measured as 76.3 and 80.1 ml kg-1 min-1 at the ages of 14 and 15 years respectively. Despite the fast rate of growth during puberty, maximal aerobic power showed seasonal variations from the age of 14, reaching a plateau at the age of 15, whereas VO2 max (ml kg-2/3 min-1) increased continuously. It is concluded that, during puberty, boys probably attain significant increases in VO2 max when appropriate amounts of endurance training are undertaken.

Aerobic endurance, anatomical factors and time properties of laser Doppler recorded skin postocclusive hyperaemia.

Aerobic endurance capacity is partly dependent on blood supply to and metabolic capacity of the active muscles. Recordings of lower limb skin postocclusive hyperaemia with laser Doppler flowmetry can differentiate between patients with lower limb atherosclerosis and healthy controls. In this study, we investigated the relationship between aerobic endurance, calf volume, common femoral artery diameter and time properties of the postocclusive laser Doppler curve. A group of 16 healthy male subjects with values for aerobic endurance which varied from those of untrained men to elite endurance trained athletes were examined. Duration of laser Doppler recorded skin postocclusive hyperaemia was significantly correlated to both aerobic power and anaerobic threshold (P less than 0.01). Hyperaemia in subjects with large common femoral artery diameter was of shorter duration (P less than 0.05). The peak and mean body mass related blood flow during hyperaemia was correlated to anaerobic threshold (P less than 0.05). These results were in agreement with previous studies indicating an effect of endurance training on the blood supply to the muscles concerned.

Sex differences in performance-matched marathon runners.

Six male and six female runners were chosen on the basis of age (20-30 years) and their performance over the marathon distance (mean time = 199.4, SEM 2.3 min for men and 201.8, SEM 1.8 min for women). The purpose was to find possible sex differences in maximal aerobic power (VO2max), anaerobic threshold, running economy, degree and utilization of VO2max (when running a marathon) and amount of training. The results showed that performance-matched male and female marathon runners had approximately the same VO2max (about 60 ml.kg-1.min-1). For both sexes the anaerobic threshold was reached at an exercise intensity of about 83% of VO2max, or 88%-90% of maximal heart rate. The females' running economy was poorer, i.e. their oxygen uptake during running at a standard submaximal speed was higher (P less than 0.05). The heart rate, respiratory exchange ratio and blood lactate concentration also confirmed that a given running speed resulted in higher physiological strain for the females. The percentage utilization of VO2max at the average marathon running speed was somewhat higher for the females, but the difference was not significant. For both sexes the oxygen uptake at average speed was 93%-94% of the oxygen uptake corresponding to the anaerobic threshold. Answers to a questionnaire showed that the females' training programme over the last 2 months prior to running the actual marathon comprised almost twice as many kilometers of running per week compared to the males (60 and 33 km, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endurance training on muscle fibre ATP-ase activity, capillary supply and mitochondrial content in man.

Seven young females were subjected to 24 weeks of intensive endurance training. Adaptive changes in myofibrillary ATP-ase activity, capillary supply and mitochondrial content were investigated with light- and electron microscopy in needle biopsies from the quadriceps femoris. 1. The average value for the maximal oxygen uptake increased from 45.7 to 57.2 (ml . kg-1 min-1) (25.2%, P less than 0.005). 2. The average number of capillaries per muscle fibre increased from 1.39 to 1.79 (28.8%, P less than 0.005). Since no significant change in fibre area was found, this suggests that a considerable number of new capillaries have been formed during the training period. 3. An increased capillary supply of all fibre types was found, being greatest for type I and smallest for type IIB. 4. The relative amount of type I fibres before and after the training period was 57.9 and 56.5% respectively (n.s.), for type IIA fibres 26.4 and 31.5% (P less than 0.005), for type IIB fibres 9.2 and 3.4% (P less than 0.005) and for type IIC fibres 0.4 and 2.2% (P less than 0.005). Thus, in the type II group, significant changes in subtypes take place during the endurance training. The data suggest that type IIAB may represent a transitional state between type IIA and IIB. 5. Correlation of capillary supply, myofibrillar ATP-ase activity and mitochondrial content (determined semiquantitatively of individual muscle fibres indicators that the capillary supply to a given fibre is more closely related to its mitochondrial content than to the fibre type as determined on the basis of myofibrillar ATP-ase activity.

Effects of active, passive or no warm-up on the physiological response to heavy exercise.

Six endurance-trained young men were subjected to a 4 min maximal aerobic treadmill run (100% of VO2 max), after active or passive warm-up or rest on separate days. The increase in body temperature during the active and passive warm-up was controlled, so that the temperature reached the same level, before the subject was exposed to the maximal exercise. On average the rectal temperature rose to 38.3 degrees C (range 38.1-38.6 degrees C). The standard work resulted in a significant higher oxygen uptake, lower lactate concentration and higher blood pH when the work was preceded by active warm-up as compared with passive or no warm-up. The difference in total oxygen uptake during the run between the active and passive warm-up procedure was 0.8 1. No significant difference in minute volume of expired air or respiratory quotient was found. It is concluded that the physiological effects of a thorough active warm-up may be of substantial benefit to athletic performance.