ISOMETRIC EXERCISE AND AGE--CARDIOVASCULAR-SYMPATHOADRENAL-METABOLIC RESPONSES

静态（等距）肌肉收缩是用力的常见组成部分

Static (isometric) muscle contractions are common components of effort in performing daily activities. The problem of static exercise becomes important since isometric contractions cause marked increase in blood pressure and catecholamine levels. This study is designed to describe the relationships among age, sex, body weight, pattern of body fat distribution, level of physical fitness, and static exercise responses. The subjects for the study are selected from three volunteer groups: participants in the Johns Hopkins Academic Teaching Nursing Home, the Baltimore Longitudinal Study of Aging (BLSA), and the Senior Athletes Study. They are divided into four age groups: 20-45, 45-59, 60-74 and 75 and over years. They are mildly to moderately obese ranging in body fat from 20 to 40% and are further subdivided into two subgroups of subjects representing upper and lower body segment type of obesity. Normal controls are lean but age and sex matched to these obese subjects. The experimental protocol is the same for all subjects: sustained hand-grip exercise on a hand dynamometer at 30% of their individual maximal voluntary force to fatigue (usually 3 - 6 minutes). Before the test, at one minute intervals during the test, and 3 minutes after its termination, blood pressure, heart rate and blood samples for catecholamines, glucose and free fatty acids are taken. To date, a total of 14 subjects have been studied from the Teaching Nursing Home and Senior Athletes groups. Studies in the BLSA participants will be initiated in the coming year. We plan to test 40 subjects in each of the 4 age groups. The study should be completed with the next year.