Six Months’ Rehabilitation Exercise Affects Lower And Higher Muscle Echo Intensity In Elderly Individuals

Abstract

Muscle echo intensity (EI) reflects the content of fat and connective tissue within a skeletal muscle. Muscle EI becomes higher with aging and/or inactivity caused by increase of fat and connective tissues, and eventually it may induce lower muscle strength. We have previously reported that the EI improved after a few months’ resistance and endurance training in elderly individuals. This result would be led by decreasing of fat and connective tissues (i.e. decrease higher EI area) and/or increasing of contractive muscle tissue (i.e. increase lower EI area); however, it is not well understood how the muscle EI change by several months rehabilitation exercise. PURPOSE: The purpose of this study was to investigate the effects of 6 months rehabilitation exercise on gradation-based muscle EI area in elderly men and women. METHODS: Five men and women (2 men and 3 women; age, 75 ± 5 years; height, 156 ± 4 cm; weight, 53 ± 9 kg) participated in this study. They performed rehabilitation exercises consisting of resistance exercises, stretching, and aerobic exercises once or twice a week for 6 months because they needed long-term care during a part of daily living. B-mode ultrasonographic transverse image was taken from rectus femoris. To obtain EI, region of interest (ROI) was set on rectus femoris as large as possible exclude fascia. Average muscle EI, which was shown by 256 gray scale level, was measured within a ROI. We also calculated cross-sectional area based on 256 grey scale level divided into 6 different components (e.g. 0-49, 50-99, 100-149, 150-199, 200-249 and 250-256 a.u.). RESULTS: Average EI decreased after six months exercise (72.70 ± 7.55 vs. 53.50 ± 15.51 a.u., p < 0.05). Lower ranged EI area was significantly increased after the exercise (0-49; 1.13 ± 0.88 vs. 1.93 ± 1.00 cm2, p < 0.05). Middle to higher ranged EI areas were significantly decreased after the exercise (100-149; 0.44 ± 0.20 vs. 0.24 ± 0.15 cm2, 150-199; 0.08 ± 0.05 vs. 0.03 ± 0.04 cm2, p < 0.05). CONCLUSIONS: Six months rehabilitation exercise improved muscle EI in elderly men and women. This result might be induced by decreasing fat and connective tissues and increasing contractile muscle tissue.