2. Materials and Methods
knee joints’, knee joints
CONTRACTION
This study employed the single-blind randomized controlled trial design to prevent the examiners from knowing if a participant belonged to the experimental or control group. This study was approved by the hospital’s clinical research ethics committee (Ministry of Health and Welfare Tsaotun Psychiatric Center Institutional Review Board IRB104056, Clinical Trial Registration Number ChiCTR-IOR-16008059). All participants were fully informed of the contents of this study beforehand and had signed a consent form.This study enrolled 80 middle-aged and elderly individuals. The inclusion criteria are as follows: (1) Individuals older than 45 years who lack regular exercise habits or have not received exercise instruction. According to the latest Taiwan Social Change Survey (TSCS), participant who answered that they exercised “several times a week” or “every day” were excluded from the study [Intervention conditions: Eligible participants were randomly assigned to three experimental groups and a control group. The vibration instrument used in this study was a commercial-grade WBV training machine (LV-1000, X-trend, Taiwan). Participants were randomly assigned to a WBV group (20 Hz, Outcome measure: Before undertaking the formal test, the participants first engaged in two familiarization exercises (for 10 s per session). The test parameters include each participant’s pre-WBV training, 3 months post-WBV training, and 6 months post-WBV training balance abilities and muscle strength, as well as the 1-year incidence of falls for all participants. Participants’ balance abilities were measured using the limits of stability (LOS) test on a balance system (Biodex Balance System, Shirley, NY, USA). The LOS test mainly challenges an individual’s center of gravity and movements within their base of support. In each test, participants are repeatedly instructed to shift their center of gravity to a randomly designated position according to the machine’s instructions and then return to the starting position afterwards. Additionally, this index (LOS) assesses participants’ ability to control their center of gravity in different directions.Data processing: Before undertaking this test, a participant’s age, height, and stability grade were input into the balance testing machine. The test results, expressed in percentage, were derived from the ratio of the actual displacement of a participant’s center of pressure under the feet to the vertical distance between the center of pressure and the target position. The score is calculated as follows: (vertical distance to the target position/sample size) × 100% This balance ability assessment system has been demonstrated to have a good validity (ICC: 0.60–0.95) [Muscle strength was measured using an isokinetic lower extremity dynamometer (Biodex System IV Pro, Shirley, NY, USA). The pretest and posttest knee extensor and flexor strength were tested along with their isokinetic concentric and eccentric muscle strength at a 60°/s angular speed.After warming up, the participants were instructed to sit on the Biodex isokinetic dynamometer. Their trunk, pelvis, lower right thigh, and ankles were secured on the seat according to the instructions on the machine to prevent them from shifting their position during the rest and affecting the test results. The relative position of the seat and the dynamometer were adjusted such that the knee joints’ centers of rotation (lateral malleoli of the tibia) are aligned with the dynamometer’s axis of rotation. Isokinetic flexor strength tests began after the calf center of gravity was corrected. The isokinetic concentric contraction mode at a 60°/s angular speed was applied during the tests. Each participant underwent three tests, with a 1-min rest between each contraction.Flexibility was measured through the sit-and-reach test, which assesses flexibility of the waist and lower limb joints. Participants are first instructed to sit on the floor or a mat with their shoes off, their thighs at shoulder width, the knee joints extended, and the toes facing upwards. A tape measure is placed between the legs. The bottom of the heel must be aligned with the 25-cm mark on the tape measure. The hands are placed on top of one another so that the middle fingers align, palms together. The participant then reaches to touch the tape measure for two seconds using their middle finger, and the farthest distance (in cm) is recorded. During the tests, the first reading is considered a practice result and the better of the latter two readings is taken as the final result [The treatment rate for falls was assessed through phone interviews and pen-and-paper questionnaires about the participants’ history of being treated for falls within the last year.The participants’ basic information and measurement variables were recorded as descriptive statistics. Chi-squared tests and one-way ANOVA were used to examine for differences between the four groups, while repeated-measure ANOVA was used to analyze the pretest and posttest differences of the descriptive statistics across all groups and the pretest and posttest differences in their LOS, muscle strength and flexibility. Data analysis was performed using SPSS 14.0 statistical software. The level of significance (α) was at 0.05 in all tests. Post-hoc analyses were performed through the Scheffe test in the case of significant between-group and pretest/posttest interactions.