Respiratory Responses during Exercise in Self-contained Breathing Apparatus among Firefighters and Nonfirefighters.

Background: Firefighters are required to use self-contained breathing apparatus (SCBA), which impairs ventilatory mechanics. We hypothesized that firefighters have elevated arterial CO when using SCBA.

Methods: Firefighters and controls performed a maximal exercise test on a cycle ergometer and two graded exercise tests (GXTs) at 25%, 50%, and 70% of their maximal aerobic power, once with a SCBA facemask and once with protective clothing and full SCBA.

Effect of rehydration schedule after four-hour head-out water immersion on running performance and recovery.

Introduction: Head-out water immersion (HOWI) results in diuresis, which could potentially limit performance after egress to land. We examined the effect of rehydration on endurance, cardiovascular stability, and overnight recovery following a four-hour thermoneutral HOWI on 12 subjects.

Methods: Twelve males completed a crossover design consisting of no hydration, replacement of fluid loss during immersion (RD), and replacement of fluid after the immersion period (RA).

Effect of wetted surface area on friction, pressure, wave and total drag of a kayak.

Using theoretical principles, the components of drag (friction D , pressure D and wave D ) of a single-seat kayak were analysed. The purpose was to examine the effect of changes in wetted surface area due to changes in kayaker's weight and the relative contribution of D , D and D to the total passive drag as function of velocity. The total passive drag values were based on experimental data collected in a single-seat kayak.

Respiratory Muscle Training and Exercise Endurance at Altitude.

Background: Climbing and trekking at altitude are common recreational and military activities. Physiological effects of altitude are hypoxia and hyperventilation. The hyperventilatory response to altitude may cause respiratory muscle fatigue and reduce sustained submaximal exercise.

Do 5% changes around maximal lactate steady state lead to swimming biophysical modifications?

Our purpose was to examine the swimming biophysical responses at velocities (v) of 97.5, 100 and 102.5% of the maximal lactate steady state (MLSS).

Respiratory Muscle Training and Cognitive Function Exercising at Altitude.

Background: Hiking and trekking often occur at altitudes up to 12,000 ft altitude. The hypoxia-induced hyperventilation at altitude paradoxically reduces arterial CO2 (Paco2). A reduction in Paco2 results in vasoconstriction of the blood vessels of the brain and thus in local hypoxia.

Is passive drag dependent on the interaction of kayak design and paddler weight in flat-water kayaking?

Drag is one of the major factors that influences kayaking performance. To focus on the drag of the kayak's hull shape and the paddlers' weight per se, the passive drag (Dp) was measured on a flat-water sprint course for one paddler with added weights. Dp was measured by an electromechanical towing device using a load cell, at incremental and constant velocities from 2.

Human Physiology in an Aquatic Environment.

Water covers over 70% of the earth, has varying depths and temperatures and contains much of the earth's resources. Head-out water immersion (HOWI) or submersion at various depths (diving) in water of thermoneutral (TN) temperature elicits profound cardiorespiratory, endocrine, and renal responses. The translocation of blood into the thorax and elevation of plasma volume by autotransfusion of fluid from cells to the vascular compartment lead to increased cardiac stroke volume and output and there is a hyperperfusion of some tissues.

Cerebral Blood Flow During Treadmill Exercise Is a Marker of Physiological Postconcussion Syndrome in Female Athletes.

Objective: Some patients with postconcussion syndrome (PCS) have reduced exercise capacity that may reflect altered central cardiorespiratory control. The purpose of this study was to evaluate control of cerebral blood flow (CBF) during exercise in females with PCS.

Setting: University Concussion Clinic.

Effects of ambient temperature on nitrogen uptake and elimination in humans.

Tissue nitrogen (N2) exchange is primarily dependent on circulation, which may be modified by body thermal status. Thermal effects on uptake and washout of N2 have not been systematically investigated earlier. In the present study of eight subjects, N2 was washed out in thermally neutral ambient conditions (TN; skin temperature (Ts) = 33.

Electrocardiogram at an altitude of 3600 m with reference to T wave depression.

Introduction: Exposure to high altitude decreases arterial oxygen saturation (Sa(O2)). Previous studies have shown decreased voltage of the T wave of the electrocardiogram (ECG) at altitudes up to 7000 m (22,966 ft) secondary to hypoxia. This pilot study explored changes in the ECG at the maximum altitude pilots can fly without supplemental oxygen.

The effects of respiratory muscle training on respiratory mechanics and energy cost.

Resistance respiratory muscle training (RRMT) increases respiratory muscle strength and can increase swimming endurance time by as much as 85%. The purpose of this study was to examine potential mechanisms by which RRMT improves exercise endurance. Eight healthy adult male scuba divers underwent experiments in a hyperbaric chamber at sea level (1 atmosphere absolute (ATA)), 2.

Negative pressure breathing increases cardiac output and nitrogen elimination in seated subjects.

During denitrogenation for rescue, crew members of an internally pressurized disabled submarine (DISSUB) must sit upright, which may hamper venous return, cardiac output and peripheral circulation. Since negative pressure breathing (NPB) might counteract this problem, denitrogenation was measured in sitting subjects performing NPB. Seven male subjects completed 125-minute nitrogen (N2) washouts breathing either 100% oxygen (O2) or a normoxic gas (21% O2 in argon) in control conditions and intermittent (I: inspirations only) or continuous (C) NPB at -10 or -15 cmH2O.

Interplay of biomechanical, energetic, coordinative, and muscular factors in a 200 m front crawl swim.

This study aimed to determine the relative contribution of selected biomechanical, energetic, coordinative, and muscular factors for the 200 m front crawl and each of its four laps. Ten swimmers performed a 200 m front crawl swim, as well as 50, 100, and 150 m at the 200 m pace. Biomechanical, energetic, coordinative, and muscular factors were assessed during the 200 m swim.

Relative effects of submersion and increased pressure on respiratory mechanics, work, and energy cost of breathing.

Submersion and increased pressure (depth) characterize the diving environment and may independently increase demand on the respiratory system. To quantify changes in respiratory mechanics, this study employed a unique protocol and techniques to measure, in a hyperbaric chamber, inspiratory and expiratory alveolar pressures (interrupter technique), inspiratory and expiratory resistance in the airways (RawI and RawE, esophageal balloon technique), nitric oxide elimination (thought to correlate with Raw), inspiratory and expiratory mechanical power of breathing, and the total energy cost of ventilation. Eight healthy adult men underwent experiments at 1, 2.

Exercise treatment for postconcussion syndrome: a pilot study of changes in functional magnetic resonance imaging activation, physiology, and symptoms.

Purpose: To compare functional magnetic resonance imaging (fMRI) activation patterns during a cognitive task, exercise capacity, and symptoms in postconcussion syndrome (PCS) patients who received exercise treatment (n = 4) with a PCS placebo stretching group (n = 4) and a healthy control group (n = 4).

Methods: Subjects completed a math processing task during fMRI and an exercise treadmill test before (time 1) and after approximately 12 weeks (time 2). Exercise subjects performed aerobic exercise at 80% of the heart rate (HR) attained on the treadmill test, 20 minutes per day with an HR monitor at home, 6 days per week.

Statin therapy depresses fat metabolism in older individuals.

Objective: Statins (3-hydroxy-3-methylglutaryl coenzyme A [HMG CoA] reductase inhibitors) reduce blood lipoproteins and reduce the risk of cardiovascular events. However, they may reduce fat metabolism. This study tested the hypothesis that total body fat oxidation is reduced by statins in older subjects and the reduction is not due to substrate availability.

Effects of different types of respiratory muscle training on exercise performance in runners.

To compare two different types of respiratory muscle training on exercise performance, a protocol was devised consisting of a combination of a 4-week, 12-session resistive respiratory muscle training (RRMT) followed by a 4-week, 12-session voluntary isocapnic hyperpnea training (VIHT) and conducted in experienced runners (4 men, 4 women). Measurements before and 5 days after training included: pulmonary function (spirometry), maximal inspiratory and expiratory mouth pressures, respiratory endurance time, maximal oxygen uptake (V(o2)max), running time to voluntary exhaustion at 80% V(o2)max, blood lactate concentration, and minute ventilation. There were no statistically significant differences in pulmonary functions and V(o2)max post-RRMT and post-VIHT compared to pre-RMT.

Cardiovascular and pulmonary responses to increased acceleration forces during rest and exercise.

Background: The reduced cardiac output (CO) secondary to increased acceleration forces (+Gz) has applicability to daily life and pathophysiology. Increased +Gz and reduced CO affect the lung, resulting in reduced oxygen transport. A variety of studies have examined tolerance to high +Gz.

Exercising divers' thermal protection as a function of water temperature.

Physiological adjustments and passive thermal insulation are not sufficient to protect divers in the cold and warm waters experienced by sport, professional and military divers. In a previous study of resting subjects, divers were protected by actively heated/cooled water that perfused a six-zone (head, torso, arms, hands, legs and feet) tube suit. Subsequently a self-contained diver thermal protection system (DTPS) was developed and used in this study to test male divers (n = 8) wearing a 6-mm foam neoprene wetsuit in water temperatures (T(W)) of 10 degrees C-39 degrees C at 4 feet in depth.

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise.

The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the G(z) axis (a (g)) ranging from 0 to 3 g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a (g).

Respiratory muscle training reduces the work of breathing at depth.

Resistance respiratory muscle training (RRMT) increases respiratory muscle and swimming performance at depths down to 17 msw. It is unknown if RRMT improves swimming performance at greater depths and if the improvements are associated with a reduced work of breathing (WOB), altered respiratory mechanics and/or improved respiratory muscle performance. Eight male subjects (30.

A preliminary study of subsymptom threshold exercise training for refractory post-concussion syndrome.

Objective: To evaluate the safety and effectiveness of subsymptom threshold exercise training for the treatment of post-concussion syndrome (PCS).

Design: Prospective case series.

Setting: University Sports Medicine Concussion Clinic.

In-situ mechanical characteristics of the tongue are not altered in the obese Zucker rat.

Study Objectives: Obese Zucker rats have more collapsible isolated upper airways, compared with their lean counterparts. The functional characteristics of the tongue as a potential mechanism for the enhanced upper airway collapsibility in the obese Zucker rat are unknown. This study measured the functional characteristics of the tongue muscle in lean and obese Zucker rats.