Changes of cardiac output during treadmill exercise by impedance cardiography

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.

Effect of pH on Physical Properties of Guinea Pig Skin / 대한피부과학회지

This study was undertaken to investigate some mechanical properties of the skin with special relatio to pH. The abdomenal skin of guinea pig was prepared and cut into appropriate skin strips(1.5mm*15mm). The pieces of skin strips were then suvject to measurement (stretching and vreaking load) using a rheometer after treatment in various pH vuffers and humectant solutions (lactic acid, PCA, citric acid). The result are summarized as follows ; 1. Treatment of the skin in the extreme acidic (pH3) solution showed significant deformity (swelling and shrinkage in length). 2. The overall measurements after treatment in the humectant solutions were not significantly different from those in standard vuffer solutions. 3. The stretching was maxiaml at pH7 and minimal in the extreme ranges of pH(pH 3 and pH11). 4. The measurement of vreaking load showed minimal value at acidic pH3 and revealed linear increments as pH increased.