The Effect of Temperature Variations on Volume Pulse. Male and female subjects were connected to three electrodes: a positive lead on the right wrist, a negative lead on left wrist, and a grounded lead on the right leg. The electrodes were subsequently attached to an ECG device (model IWX/214, iWorx). In addition, a pulse plethysmograph (model PT-104) was attached on the volar surface of the subject’s distal segment of the middle finger. After a minute of quiet resting, a bag containing ice cold water (0ºC) was placed on the subject’s left forearm. ECG and volume pulse recordings following the removal of the bag were used to indicate the recovery progress leading to homeostasis. Similarly, the effect of heat stress was measured by placing a bag of warm water (50ºC) on the subject’s left forearm. The information obtained from the ECG was used to calculate pulse wave amplitude (volts), beat period (seconds/beat), heart rate (BPM), and R-Pulse (seconds).
ECG and Volume Pulse after Leg Exercise. The same group of subjects were instructed to perform a random physical exercise that utilized leg muscles, such as linear jumping or walking stairs, for three minutes. Immediately following the exercise, ECGs formatted to show pulse and pulse integral were recorded until the subject’s heart rate and breathing rates returned to normal – baseline. The information obtained from the ECG was used to calculate the average R-wave amplitude (volts), beat period, heart rate, P-R interval (seconds), Q-T interval (seconds), T-P interval (seconds), R-pulse interval, and pulse wave amplitude at 30 second intervals throughout the recovery period.
ECG and Volume Pulse after Hand Exercise. Subjects connected to the ECG device were instructed to sit quietly while grasping a hand dynamometer (model FT-325) with the plethysmograph attached to their middle finger. Subjects rhythmically squeezed the dynamometer bulb until the forearm muscles fatigued. Immediately following the exercise, ECGs were recorded until the amplitude of the finger signal attained a reasonably constant level. The information obtained from the ECG was used to calculate the subject’s heart rate at rest and at 30 second intervals into the recovery period, the average R-pulse amplitude, R-wave amplitude, and pulse wave amplitude.
ECG and Volume Pulse after Coffee Consumption. Male subjects selected for this study were instructed to drink one cup of unsweetened coffee containing approximately 100 milligrams of caffeine. Subjects had fasted two hours prior to treatment and were non-smokers. Following consumption, subjects were immediately connected to an ECG with a plethysmograph attached to their middle finger. The information obtained from the ECG was used to calculate the average beat period, heart rate, R-pulse interval, and pulse wave amplitude.
Statistical Analysis. Significant differences observed between ECG measurements taken at rest versus measurements taken at each variable tested were determined by the Student t-test using Sigmaplot. Data are presented as means ± standard error; statistical significance was accepted at P ≤ 0.05.