Prevalence of exercise-induced arterial hypoxemia in healthy women.

Purpose: Exercise-induced arterial hypoxemia (EIAH) is reported to occur in approximately 50% of highly trained male endurance athletes. Few studies have examined EIAH in women and the prevalence remains unclear. It has been reported that some female subjects who develop EIAH possess maximal oxygen consumption (VO2max) values that are within 15% of their predicted value.

Sex differences in respiratory exercise physiology.

Respiratory exercise physiology research has historically focused on male subjects. In the last 20 years, important physiological and functional differences have been noted between the male and female response to dynamic exercise where sex differences have been reported for most of the major determinants of exercise capacity. Female participation in competitive and recreational sport is growing worldwide and it is universally accepted that participation in regular physical activity is of health benefit for both sexes.

Physiology of sport rock climbing.

Rock climbing has increased in popularity as both a recreational physical activity and a competitive sport. Climbing is physiologically unique in requiring sustained and intermittent isometric forearm muscle contractions for upward propulsion. The determinants of climbing performance are not clear but may be attributed to trainable variables rather than specific anthropometric characteristics.

Effects of upper extremity exercise training on peak aerobic and anaerobic fitness in patients after transplantation.

We found that patients with transplants, regardless of transplant type, and sedentary control subjects experience significant increases in aerobic fitness after 10 weeks of Dragon boat training. However, the magnitude of improvement in aerobic fitness depends on the transplant type, with patients having cardiac transplant experiencing greater relative changes in response to training than patients with noncardiac transplant. It also appears that patients with cardiac and noncardiac transplants have an increased reliance on anaerobic energy systems during exercise conditions compared with healthy control subjects.

[The John Sutton Lecture: CSEP, 2002]. Pulmonary system limitations to exercise in health.

It is commonly held that the structural capacity of the normal lung is "overbuilt" and exceeds the demand for pulmonary O2 and CO2 transport in the healthy, exercising human. On the other hand, the adaptability of pulmonary system structures to habitual physical training is substantially less than are other links in the O2 transport system. Accordingly, in some highly fit, and even in some not so fit habitually active individuals, the lung's diffusion surface, airways, and/or chest-wall musculature are underbuilt relative to the demand for maximal O2 transport.

Physiological responses to indoor rock-climbing and their relationship to maximal cycle ergometry.

Purpose: To quantify the cardiorespiratory responses to indoor climbing during two increasingly difficult climbs and relate them to whole-body dynamic exercise. It was hypothesized that as climbing difficulty increased, oxygen consumption ([V02] and heart rate would increase, and that climbing would require utilization of a significant fraction of maximal cycling values.

Methods: Elite competitive sport rock climbers (6 male, 3 female) completed two data collection sessions.

Respiratory influences on sympathetic vasomotor outflow in humans.

We have attempted to synthesize findings dealing with four types of respiratory system influences on sympathetic outflow in the human. First, a powerful lung volume-dependent modulation of muscle sympathetic nerve activity (MSNA) occurs within each respiratory cycle showing late-inspiratory inhibition and late-expiratory excitation. Secondly, in the intact human, neither reductions in spontaneous respiratory motor output nor voluntary near-maximum increases in central respiratory motor output and inspiratory effort, per sec, influence MSNA modulation within a breath, MSNA total activity or limb vascular conductance.

Respiratory muscle training in healthy individuals: physiological rationale and implications for exercise performance.

The respiratory system has traditionally been viewed to be capable of meeting the substantial demands for ventilation and gas exchange and the cardiopulmonary interactions imposed by short-term maximum exercise or long-term endurance exercise. Recent studies suggest that specific respiratory muscle (RM) training can improve the endurance and strength of the respiratory muscles in healthy humans. The effects of RM training on exercise performance remains controversial.

Threshold effects of respiratory muscle work on limb vascular resistance.

The purpose of this study was to determine whether the human diaphragm, like limb muscle, has a threshold of force output at which a metaboreflex is activated causing systemic vasoconstriction. We used Doppler ultrasound techniques to quantify leg blood flow (Q(L)) and utilized the changes in mouth twitch pressure (DeltaP(M)T) in response to bilateral phrenic nerve stimulation to quantify the onset of diaphragm fatigue. Six healthy male subjects performed four randomly assigned trials of identical duration (8 +/- 2 min) and breathing pattern [20 breaths/min and time spent on inspiration during the duty cycle (time spent on inspiration/total time of one breathing cycle) was 0.

Effects of expiratory muscle work on muscle sympathetic nerve activity.

We hypothesized that contractions of the expiratory muscles carried out to the point of task failure would cause an increase in muscle sympathetic nerve activity (MSNA). We measured MSNA directly in six healthy men during resisted expiration (60% maximal expiratory pressure) leading to task failure with long [breathing frequency (f(b)) = 15 breaths/min; expiratory time (TE)/total respiratory cycle duration (TT) = 0.7] and short (f(b) = 30 breaths/min; TE/TT = 0.

Fatiguing inspiratory muscle work causes reflex reduction in resting leg blood flow in humans.

1. We recently showed that fatigue of the inspiratory muscles via voluntary efforts caused a time-dependent increase in limb muscle sympathetic nerve activity (MSNA) (St Croix et al. 2000).

Influence of inhaled nitric oxide on gas exchange during normoxic and hypoxic exercise in highly trained cyclists.

This study tested the effects of inhaled nitric oxide [NO; 20 parts per million (ppm)] during normoxic and hypoxic (fraction of inspired O(2) = 14%) exercise on gas exchange in athletes with exercise-induced hypoxemia. Trained male cyclists (n = 7) performed two cycle tests to exhaustion to determine maximal O(2) consumption (VO(2 max)) and arterial oxyhemoglobin saturation (Sa(O(2)), Ohmeda Biox ear oximeter) under normoxic (VO(2 max) = 4.88 +/- 0.

Alveolar epithelial integrity in athletes with exercise-induced hypoxemia.

The effect of incremental exercise to exhaustion on the change in pulmonary clearance rate (k) of aerosolized (99m)Tc-labeled diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) and the relationship between k and arterial PO(2) (Pa(O(2))) during heavy work were investigated. Ten male cyclists (age = 25 +/- 2 yr, height = 180.9 +/- 4.

Relationship between decreased oxyhaemoglobin saturation and exhaled nitric oxide during exercise.

Decreases in oxyhaemoglobin saturation (SaO2) are frequently observed in highly trained male endurance athletes during heavy work and has been termed exercise-induced hypoxaemia (EIH). Ventilation perfusion (VA/Q) mismatching and diffusion limitations are thought to be responsible. Nitric oxide (NO), a potent vasodilator, is present in the exhaled air of resting and exercising humans.

Exhaled nitric oxide during exercise.

Endogenously produced nitric oxide (NO) is detectable in the exhaled air of resting humans, and the amount of exhaled NO increases during exercise. It is believed that NO is likely to have an important role in the normal physiological response to exercise. Despite accumulating evidence of exhaled NO during exercise, the effects and relevance of NO to exercise are not yet completely understood.

The effect of repeat exercise on pulmonary diffusing capacity and EIH in trained athletes.

Purpose: The purpose of this study was to determine the effects of repeated heavy exercise on postexercise pulmonary diffusing capacity (DL) and the development of exercise induced arterial hypoxemia (EIH).

Methods: 13 endurance-trained, male athletes (age = 27+/-3 yr, height = 179.6+/-5.

The time course of pulmonary diffusing capacity for carbon monoxide following short duration high intensity exercise.

We investigated the time course of changes in post-exercise pulmonary diffusing capacity for carbon monoxide (DLCO), membrane diffusing capacity (DM), and pulmonary capillary blood volume (VC) in highly trained (HT), moderately trained (MT) and untrained (UT) male subjects (n = 8/group). Subjects were assigned to groups based on their aerobic capacity from a preliminary VO2max test (HT > or = 65, MT = 50-60, UT < or = 50 ml x kg(-1) x min(-1)). Resting (BASE) DLCO, DM and VC were obtained, then subjects cycled to fatigue at the highest workrate attained during the preliminary tests.

Comparison of aero-bars versus traditional cycling postures on physiological parameters during submaximal cycling.

The purpose of this investigation was to quantify the difference in energy expenditure between traditional cycling handlebars and aero-bars during outdoor submaximal cycling. Eleven trained cyclists (age = 29.3 +/- 1.