Effects of Low-Intensity Exercise Training on Tissue Oxygen Saturation of Lower-Extremity in Community-Dwelling Older Adults

Abstract

Muscle strength and muscle oxygen saturation are two typical indicators for the evaluation of exercise effects in rehabilitation and sport medicine. The aim of this study was to compare the effects of low-intensity exercise training on muscle strength and muscle oxygen saturation monitored by near infrared spectroscopy (NIRS) in older adults. Eighteen healthy community-dwelling older adults, age mean (SD), 78.7 (7.3) years, were recruited. Ten subjects (exercise group) participated 6-week training program for lower-extremity, and the others were control. The training program was composed of 15-minute exercise course using three machines for lowerextremities training three times a week for six weeks. The intensity of machines were adjusted to 50% of one repetition maximum for each participants respectively. Heart rate, blood pressure, blood oxygen, muscle strength and muscle oxygen saturation, were measured before and after the 15-minute course in week zero (Week 0, before the 6-week training program) and 7th week (Week 7, after the training program). The Student’s t-test was used to compare the difference of these variables between groups. The effective fall in quadriceps muscle oxygen saturation, Deff, is defined as the decrease in oxygen saturation from quiet baseline (BL) to the end of one 15-minute course (Post-exercise, PE). After 6-week training program, Deff did not change in the exercise group, while it decreased significantly in control group. Quadriceps muscle strength did not change after 6-week program in the exercise group, but decreased about 6% in the control group (not significant). Heart rate, blood pressure and blood oxygen were unaffected in the exercise group and the control group. The ambient temperatures were 25.8 .. and 19.9 .. for Week 0 and Week 7 respectively (p<0.0001). The training program counterbalance the muscular function decline due to seasonal variation from the end of autumn to winter for subjects participating the exercise program, while the function declined in control group. We suggest the non-invasive measurement of muscle oxygen could be used to assess the effect of physical activity program in community.