Abstract
BackgroundHigher muscle echo intensity (EI) reflects higher content of fat and/or connective tissue within skeletal muscle, eventually inducing lower muscle strength, physical dysfunction, and metabolic impairment. Continuous exercise decreases muscle EI in older individuals; however, it is not well understood how several months’ rehabilitation exercise affects gradation-based EI. The purpose of this study was to investigate the effects of 6 months of rehabilitation exercise on gradation-based higher and lower EI in older men and women.MethodsTwenty-seven men and women (7 men, 20 women; age, 75.6 ± 6.4 years; height, 154.3 ± 8.5 cm; weight, 55.8 ± 9.7 kg) participated in this study. This study was a one-group before-and-after trial. They needed long-term care for activities of daily living. They performed rehabilitation exercises consisting of resistance exercises using a hydraulic resistance machine, stretching, and aerobic exercises using a recumbent bicycle once or twice a week for 6 months. B-mode ultrasonographic transverse image was taken from thigh muscles, e.g., rectus femoris, vastus lateralis, and biceps femoris. We calculated gradation-based cross-sectional area (CSA) from thigh muscles by dividing 256 greyscale level to 10 different components levels (e.g., 0–24, 25–49, 50–74, …, 200–224 and 225–249 a.u.).ResultsLowest EI (e.g., 0–24 a.u.) CSA of thigh muscle was significantly increased after the exercise (0.3 ± 0.3 to 1.0 ± 0.8 cm2; P < 0.05). Middle to higher EI (e.g., 50–74, 75–99, 100–124, 125–149, 150–174, 175–199 and 200–224 a.u.) CSAs were significantly decreased from 23.0 to 68.7% after the exercise (P < 0.05).ConclusionsSeveral months’ rehabilitation exercise affected both lower and higher EI in older men and women. This result suggests that rehabilitation exercise changes muscle composition by increasing contractile muscle tissue and decreasing fat and connective tissues.
Highlights
Higher muscle echo intensity (EI) reflects higher content of fat and/or connective tissue within skeletal muscle, eventually inducing lower muscle strength, physical dysfunction, and metabolic impairment
muscle thickness (MT) in rectus femoris (RF), vastus intermedius (VI)-anterior, VI-lateral, Biceps femoris (BF) and thigh muscles were significantly increased after 6 months of exercise (P < 0.05)
In the RF, Vastus lateralis (VL), BF and thigh muscles, the average EI significantly decreased after the exercise compared with before the exercise (P < 0.05)
Summary
Higher muscle echo intensity (EI) reflects higher content of fat and/or connective tissue within skeletal muscle, eventually inducing lower muscle strength, physical dysfunction, and metabolic impairment. The purpose of this study was to investigate the effects of 6 months of rehabilitation exercise on gradation-based higher and lower EI in older men and women. Muscle quality, determined by the content of IntraMAT and/or connective tissue within the muscle, is negatively associated with locomotive functions and muscle glucose metabolism, eventually inducing a decrease in activities of daily living (ADL) and diabetes [3, 4]. The intensity of traditional resistance and endurance training have been determined based on onerepetition maximum and ventilatory threshold [10, 14]; there have been challenges associated with measuring these parameters in older adults because of higher blood pressure, joint pain, and physical disability. Intensity is one of the key factors in the evaluation of the exercise effect; it is speculated that the change in physiological muscle parameters in older individuals would be difficult to ascertain by low-intensity rehabilitation exercise
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