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Christopher C Dunbar

Publications and source records attributed to Christopher C Dunbar.

4 recordsLinked to original sources
PubMed2005

Usefulness of P-wave morphology during submaximal treadmill exercise to predict coronary artery disease.

Standard electrocardiographic criteria for exercise testing require near maximal exertion and fail to detect ischemia in the presence of previous infarction or conduction or repolarization abnormalities, in women, or in the presence of certain drugs. Changes in P-wave morphology have been suggested as having diagnostic utility; however, no specific criteria exist, and it is not clear which changes are most useful. This investigation evaluated the ability to detect the presence of coronary artery disease by examining changes in P-wave morphology during exercise. A group of 123 consecutive patients underwent maximum (symptom-limited) exercise nuclear stress tests. The electrocardiograms at rest, 2 minutes of exercise, 50% of maximum exercise time, maximum exercise, and 3 minutes of recovery were analyzed for the duration of the P wave in lead II, the duration of the terminal negative component of the P wave in lead V1, the amplitude of the terminal negative component of the P wave in lead V1, and the duration of the P wave in lead V5. These variables were then analyzed for their relation to the presence of perfusion defects. Of all the P-wave criteria tested, a change in amplitude of the negative component of the P wave in lead V1 from at rest to 50% of maximum exercise time of <0.025 mV was the most predictive of coronary artery disease.

Adult↗
PubMed2004

Using RPE to regulate exercise intensity during a 20-week training program for postmenopausal women: a pilot study.

Feelings of effort sense quantified via the Borg Rating of Perceived Exertion (RPE) scale have been validated for regulating exercise intensity. Most studies validating RPE for exercise prescription have used young, male subjects and only a few exercise sessions. As part of a larger study we examined the accuracy of RPE for regulating exercise intensity in a group of postmenopausal women. Six women (70.0+/-7.1 yr.) were given a maximal graded exercise test. Target RPEs equivalent to 40%, 50% and 60% VO2 max were developed from this test using standard techniques. These RPEs were used to regulate intensity during a 20-wk. training program. During the initial 5 wk. of training target intensity was increased from 40% to 60% VO2 max and exercise duration from 15 to 30 min. Accuracy of exercise intensity regulation was determined by comparing the heart rate during exercise to a target heart rate equivalent to the desired %VO2 max. At Week 2 of training (target 40% VO2 max) the mean intensity produced did not differ from target. During Weeks 4 (target 50% VO2 max), 6 and 10 of training (target 60% VO2 max) the mean exercise intensity was below target. At Week 20 the mean intensity produced was not different from target. This suggests that elderly women can accurately use RPE to regulate exercise intensity, but at intensities above 40% VO2 max an acclimation period is needed.

Aged↗
PubMed2002

Effect of naloxone on perceived exertion and exercise capacity during maximal cycle ergometry.

We assessed the effects of naloxone, an opioid antagonist, on exercise capacity in 13 men and 5 women (mean age = 30.1 yr, range = 21-35 yr) during a 25 W/min incremental cycle ergometer test to exhaustion on different days during familiarization trial and then after 30 mg (iv bolus) of naloxone or placebo (Pl) in a double-blind, crossover design. Minute ventilation (Ve), O(2) consumption (Vo(2)), CO(2) production, and heart rate (HR) were monitored. Perceived exertion rating (0-10 scale) and venous samples for lactate were obtained each minute. Lactate and ventilatory thresholds were derived from lactate and gas-exchange data. Blood pressure was obtained before exercise, 5 min postinfusion, at maximum exercise, and 5 min postexercise. There were no control-Pl differences. The naloxone trial demonstrated decreased exercise time (96% Pl; P < 0.01), total cumulative work (96% Pl; P < 0.002), peak Vo(2) (94% Pl; P < 0.02), and HR (96% Pl; P < 0.01). Other variables were unchanged. HR and Ve were the same at the final common workload, but perceived exertion was higher (8.1 +/- 0.5 vs. 7.1 +/- 0.5) after naloxone than Pl (P < 0.01). The threshold for effort perception amplification occurred at approximately 60 +/- 4% of Pl peak Vo(2). Thus we conclude that peak work capacity was limited by perceived exertion, which can be attenuated by endogenous opioids rather than by physiological limits.

Adult↗