Biomedical subjects

Michael L Walsh

Publications and source records attributed to Michael L Walsh.

4 recordsLinked to original sources

PubMed2006

Volitional hyperventilation during ramp exercise to exhaustion.

The purpose of this study was to determine whether volitional hyperventilation at 20 L x min(-1) above normal exercise values affected exercise duration while performing ramp exercise to exhaustion. Nine healthy subjects performed a ramp exercise test to exhaustion. On a subsequent test they hyperventilated, with the aid of visual and audio feedback, at 20 L x min(-1) greater than their initial test. Ramp exercise time to exhaustion was substantially reduced from 771.6 +/- 85.2 s to 726.6 +/- 86.6 s (p < 0.002) with the additional hyperventilation. Subjects underwent 2 more ramp exercise tests and performed a 5 s maximum voluntary ventilation or a forced vital capacity test at work rates corresponding to rest, below lactate threshold (LT), above LT, immediately after exercise, and 3 min recovery. Generally, the flow rates were not affected by exercise below LT and were enhanced during above-LT exercise, exhaustion, and recovery. This indicated a change in pulmonary function that is dependent on exercise intensity. In spite of this increased ability to generate high flow rates, exercise performance was diminished when respiratory muscle work was increased volitionally by 20 L x min(-1), indicating a strong coupling between respiratory muscle work and fatigue during ramp exercise in normal subjects.

Adult↗

PubMed2006

Heart rate, mean arterial blood pressure, and pulmonary function changes associated with an ultraendurance triathlon.

OBJECTIVE: We studied 8 triathletes competing in the 3-day World Ultraman Championships (day 1: 10-km swim, 165-km bike; day 2: 261-km bike; day 3: 85-km run) to determine the effect of extreme physical exertion on heart rate (HR), mean arterial blood pressure (MAP) and pulmonary function, and their relation to overall athletic performance. METHODS: Baseline HR, MAP and pulmonary function measurements were made 2 days before the start of competition. During the competition, HR and MAP measurements were made less than 30 minutes before the start and 10 minutes after the finish each race day. Pulmonary function was measured within 5 minutes of the finish each race day. RESULTS: Forced vital capacity and forced expiratory volume in 1 second (FEV1.0) were reduced from baseline at the end of each race day. Peak expiratory flow (PEF) was reduced from baseline on days 1 and 3. Lower baseline resting HR was correlated (r = 0.77, P = .021) with faster total race times. The decreases in FEV1.0 and PEF over the whole race also correlated with performance (r = 0.77 and 0.93). Multiple regression analysis of baseline data indicated that HR and MAP had the strongest association with total race time prediction (54% and 19% of total). However, when declines in pulmonary function over the total race were also included, PEF was found to be associated with 87% of the total race time prediction. CONCLUSIONS: The strong association in the decline in PEF to race time, though just correlative, suggests a link between pulmonary function and ultratriathlon performance.

Adult↗

PubMed2004

Cardiopulmonary physiology and responses of ultramarathon athletes to prolonged exercise.

The purpose of this study was to determine the changes of pulmonary function and autonomic cardiovascular control after an ultramarathon and their relation to performance. Eight entrants to the Canadian National Championship 100-km running race participated in the study. Pulmonary function and 30-s maximum voluntary ventilation (MVV30s) tests were conducted one day before the race and within 5 minutes of race completion. Heart rate and blood pressure data were collected 30 min before and 5 min after the race as well as during a 10-min stand test one day prior to the race. During the race, beat-by-beat R-R interval data were collected over the first and last 20 km. The results showed that MVV30s and MVV30s tidal volumes were reduced postrace (p < 0.001). Prerace supine total harmonic variation (p < 0.01) and prerace MVV values (10 s to 30 s) (p < 0.05) were correlated with race finish time. The changes in pulmonary function and MVV30s values from pre- and postrace were not significantly correlated to race performance. We conclude that maximal sustainable ventilatory power and dynamic autonomic cardiovascular control are important factors in determining overall performance in an ultramarathon.

Adult↗

PubMed2002

Effects of ischaemia on subsequent exercise-induced oxygen uptake kinetics in healthy adult humans.

Leg muscles were occluded (33 kPa) prior to exercise to determine whether the induced metabolic changes, and reactive hyperaemia upon occlusion release just prior to the exercise, would accelerate the subsequent oxygen consumption (VO2) response. Eight subjects performed double bouts (6 min duration, 6 min rest in-between) of square wave leg cycle ergometry both below and above their lactate threshold (LT). Prior to exercise, large blood pressure cuffs were put around the upper thighs. Occlusion durations were 0 min (control), 5 min and 10 min. Ischaemia was terminated within 5 s prior to exercise onset. Heart rate, VO2, ventilatory rate (V(E)), electromyogram (EMG) and haemoglobin/myoglobin (Hb/Mb) saturation were recorded continuously. Single exponential modelling demonstrated that, compared to control (time constant = 53.9 +/- 13.9 s), ischaemia quickened the VO2 response (P < 0.05) for the first bout of exercise above LT (time constant = 48.3 +/- 14.5 s) but not to any other exercise bout below or above LT. The 3-6 min integrated EMG (iEMG) slope was correlated to the 3-6 min VO2 slope (r = 0.73). Hb/Mb saturation verified the ischaemia but did not show a consistent relation to the VO2 time course. Reactive hyperaemia induced a faster VO2 response for work rates above LT. The effect, while significant, was not large considering the expected favourable metabolic and circulatory changes induced by ischaemia.

Adult↗