Participants
Participants were recruited by advertisements placed on web pages, in local newspapers, journals, posters, and flyers throughout the city of Cologne and surrounding areas. Initially, each participant completed a health questionnaire and submitted a medical clearance certificate.
Exclusion criteria included: severe heart diseases; respiratory, renal, or hepatic problems; severe osteoporosis; unstable diabetes; neurological diseases or arterial hypertension; diagnosed gait disorders; artificial joints and need of walking aids for gait; and one or more falls during the last 6 months. Prospective participants who reported to have fallen were not included at this stage of the study in order to draw a homogenous sample. Prior to analysis, all performance data was anonymous. Participants were tested on three different days at 1-week intervals (on the same day of the week) in a test–retest design by the same researcher. Participants were required to maintain their usual behavior (nutrition, hydration, and physical activity) over the duration of the study. To avoid circadian variations in the performance, all participants performed their measurements at the same time of the day. The duration of the study was 10 weeks. This study was approved by the Ethic Committee of the German Sport University Cologne, and all participants signed a written informed consent form before study participation.
The sample consisted of 29 untrained, healthy participants (11 men and 18 women, M = age: 68.8 ± 5.3 years, mean body mass index: 24.4 ± 2.5 kg/m2). One of the participants had mild osteoporosis, seven with stable diabetes, two with a slight scoliosis, and one was a smoker. Four participants performed strength training once a week and completed the self-reported physical performance (using a five-point scale from very poor to very good) survey. All of the participants were rated between medium and very good. Participants wore their usual footwear, which was identical on each test day.
Instruments
Layout of the MSOT
The MSOT integrated different ground surfaces that simulated different locations and tasks were reported with high incidences of falls in previous studies [4, 20, 32]. To fulfill these presuppositions, they were minimized into a track of 10 m. This track provides a functionally oriented assessment of real-life conditions and tasks to the environmental conditions regularly experienced by older adults. The primary object was to reproduce a situation similar to that experienced in the real world by older adults. The MSOT was developed by sport scientists, working in the field of movement science, sport gerontology, and fall prevention. Initially, specific fall movements and obstacles were researched and discussed, which resulted in a selection of suitable obstacles to be implemented. The developed track was tested by individual participants, discussed with colleagues, and modified on the basis of their feedback. At the end of the pilot phase, the final version of the MSOT was determined and documented.
The total length of the test track was 10 m (cf. Fig. 1; Appendix Fig. 3). The first and last meters provide space for acceleration and deceleration; therefore, the distance timed includes only the intermediate distance of 8 m (testing zone). The testing zone consists of different surface conditions and obstacles to overcome while walking (cf. Fig. 1; Appendix Fig. 3). After 0.5-m flat surface, the first obstacle (length: 2 m) simulates road kerbs. It is constructed of a wooden box (step on 10 cm height, step off 8 cm height; length: 0.6 m) and a 2-cm high area (0.8 m length). Together with a second box (step on 13 cm height, step off 15 cm height; length: 0.6 m), the first obstacle should simulate different kerb heights and edges located on pavements or in the home.
Additionally, this is followed by an area with fixed round pebble stones on a length of 0.6 m, as a simulation of a path in a municipal park or in the garden. The next surface condition is similar to an uneven forest or garden path in the form of two Terrasensa® plates (Ludwig Artzt GmbH, Dornburg, Germany) with a length of 1 m. Stepping off the plates, there is a 1.20 m long carpet with artificial turf integrated onto the pathway, followed by wooden plates (0.6 m), similar to that found on a terrace. The track ends with a stairs element. At first, there are three stairs upwards, then a small flat area on top, and three stairs downwards. The flat surface comprises of 0.4 m prior to 8 m at the end. The stairs element has a total length of 1.70 m; each step is 17 cm high and 29 cm deep (according to German standards-DIN for stairs). The final element reproduces basic stair climbing or, in combination with the previous elements, a walk from the garden into the house. The MSOT was developed in relation to the general recommendations for gait analysis [28]. A flat track of 12 m length and 2 m width is needed to put the MSOT into practice. The integrated objects can be handled by two persons and need a storage area of 2 m2.
Measurements
The walking time in the 8-m testing zone was taken using a digital stop watch on 1/100 s. To exclude subjective influences of the researcher on the test and handling the digital stop watch, we used the three first trials on flat ground to compare the results with the data of a gait analysis system RehaWatch (Hasomed GmbH, Magdeburg, Germany). Results showed high correlations from r = .90 to .97 (p < .001). A stop watch was used in terms of future usability under practice conditions with older adults in the field. Because of the high correlations between the two measures, using the digital stop watch seems to be justifiable.
The time commenced when the first foot of the participant(s) made contact with the ground in the testing zone and stopped at the first contact out of the 8 m zone. The 8-m testing zone was highlighted with dark green tape to make measuring easier for the researcher but not to cause distraction to the participant. The participants were unaware that their time was being recorded during the testing zone. This approach was considered to prevent unwanted influence on acceleration and deceleration. The number of steps required for the 8-m distance was counted with a handheld counter for calculating cadence (steps per minute). See Appendix, for the instructions.
Testing procedures
The MSOT was conducted in an indoor environment. Participants walked on the flat surface (laboratory/floor surface) for 10 m. The initial trials were performed as a physical warm-up and to become familiar with their habitual gait velocity. Afterwards, participants received instructions to walk the entire distance of the MSOT (10 m) with their habitual gait velocity as safely as possible.
The researcher provided the participants with the instruction, “Please gear up for the start of the measurement,” which was given in front of the yellow-marked line in a parallel stance. At the end of the track, participants had to stop with their toes behind the second yellow line (after 10 m), again with a parallel stance. The researcher walked alongside but slightly behind the participant to ensure their safety. The stop watch and the counter were attached by a cord at the wrist of the researcher.
On each test session, the same testing procedure was applied with three trials on flat ground followed by three trials on the MSOT (cf. Fig. 2). To evaluate the requirement of a potential familiarization session, three sessions were executed. As a result, additional information about the consistency of older adults in their test performance should be assessed. Total test duration was approximately 20 min per participant for the six trials. The rest between trials was 60 s. A researcher (a sport scientist) was trained by the lead researcher, in this case, the primary author, in measuring the participants with the MSOT for each trial and was specifically instructed in the sequential arrangement by the lead researcher of the MSOT.
Statistical analysis
According to Hopkins [14] and based on an a priori power analysis, a sample size of 27 participants was estimated to detect a size effect of 0.5 with a power of 0.8118, an alpha of <.05, and a critical t of 1.71. Power analyses were performed with the software GPower (GPower, v3.1.3, University of Dusseldorf, Germany). In the field of reliability research, the used significance level and power are the commonly applied ones [16]. Conducting a study with three measurement days and a sample size of 30 participants, a standardized error of measurement (SEM) would be assumed in a range of SEM ×/÷ 1.2 (the lower limit is the observed value divided by 1.20 and the upper limit is the observed value times 1.20), which is equivalent to the 95 % confidence interval [14]. The smallest detectable difference (SDD) was estimated on the basis of the coefficient of variation (CV) [3, 26].
The normal distribution (Shapiro–Wilk test), homoscedasticity (Levene test) of the data, and Spearman's correlation coefficient (r
s) were calculated with the statistical software IBM SPSS Statistics 19.0 for Windows (International Business Machines Corporation, Armonk, NY, USA). If no normal distribution and/or homoscedasticity were provable, a logarithmic transformation was calculated. The calculations for reliability were conducted with the excel spreadsheet “xrely.xls” (Hopkins, 2011, Auckland, New Zealand) in Microsoft Office Excel 2007 (Microsoft Corporation, Redmond, USA). An alpha ≤0.05 was considered statistically significant.
To test the reliability between the specific trials and between sessions, the relevant parameters for absolute reliability [14, 15] were: mean difference (MD), CV, standardized MD (sMD), and standardized standard error of measurement (sSEM) and for relative reliability [1]: intraclass correlation coefficient (ICCr(2,1)) and r
s. Objectivity is given if there is good reliability and low changes between the three sessions, so that a subjective influence of the testing person is excluded. Additionally, a comparison of the single three trials in one test session and also between the sessions was used. Therefore, ANOVA with repeated measurements or a Friedman test was conducted. If there was no sphericity given, the Greenhouse-Geisser correction was used. Significant differences were examined with Bonferroni post hoc test.