Background: The Senior Fitness Test is a reliable and valid battery of individual tests which collectively measure the strength, balance, and endurance necessary to perform activities of daily living. These tests require little equipment or cost to administer, and are commonly administered in both clinical and community settings. However, with recent and rapid advancements in technology, there is now frequent use of wearable sensors to assess and quantify mobility tasks. It was the primary aim of the present study to compare the relative and absolute test-retest reliability of body-worn sensors vs. manual assessment of Senior Fitness Test components. Methods: Participants (65 years and older) attended a single 2-hour test session at a university academic building, where they performed two blocks of 3 tests (30-Second Chair Stand, 8-Foot Up-and-Go, and 6-Minute Walk Test) with a 45 minute to one hour rest in between blocks. Ambulatory Parkinson's Disease Monitoring (APDM) Opal sensors and stopwatch methods simultaneously measured the intended outcomes for each test. Test-retest relative reliability for the fitness tests was assessed with intra-class correlation coefficients (ICC (2,1) ). The agreement between test and retest was assessed by calculating minimum detectable change, which reflects the smallest amount of absolute change from test to retest that can be considered real. Results: Participants included 17 females and 11 males (Age=70.6±5.4 years; Body Mass=70.6±15.3 kg; Height=1.66±0.08m). All manual 6-Minute Walk Test outcomes exhibited excellent test-retest reliability (ICC≥0.96). The same was true of APDM, except for turn duration (ICC>0.74) and the number of steps in turn (ICC>0.61). Test-retest reliability for the 30-Second Chair Stand and 8-Foot Up-and-Go were excellent for the manual method (ICC>0.83 and >0.88, respectively), but were poor for APDM (ICC>0.41 and >0.28, respectively). Minimum detectable change was similar between the APDM and manual methods for 6-Minute Walk Test cadence (6.8 vs. 6.6 steps/min, respectively) and gait speed (0.11 vs. 0.13 m/s, respectively). There were substantial differences between manual and APDM minimum detectable change for the 30-Second Chair Stand and 8-Foot Up-and-Go, with APDM requiring approximately twice as much change, compared with manual. Conclusions: Both the APDM system and manual methods reliably and validly assessed gait speed and cadence during the 6-Minute Walk Test, though it should be noted that APDM only successfully recorded and reported data for 2 out of every 3 participants. The manual method of assessing the 8-Foot Up-and-Go and 30-Second Chair Stand was more valid and reliable than the APDM method.

Background: There appears to be an undisputed strong relationship between isometric handgrip strength (HGS) and functional fitness test performance, ability to perform activities of daily living (ADLs), and mortality, but the extreme diversity in how HGS data are interpreted make it difficult to utilize the assessment in a meaningful way. The present study aimed to simplify this interpretation by establishing a single and meaningful universal HGS cutoff that would inform the test administrator whether or not additional functional fitness testing was warranted. It was hypothesized that subjects scoring above the HGS cutoff would self-report fewer functional limitations, compared with subjects scoring below the cutoff. It was also hypothesized that subjects scoring above the HGS would perform better on each functional fitness test outcome, compared with subjects scoring below the cutoff. Methods: Male (n=24; Age=62.3±14.3 years) and female (n=59; Age=64.7±13.0 years) subjects were recruited to take part in the Steps Taken Against Neuromuscular Decline (STAND) Initiative, a longitudinal study of aging. The present study is a cross-sectional assessment of the baseline data from the first 83 subjects. Subjects self-reported their perceived ability to complete the variety of ADLs included in the Composite Physical Function Scale (maximum score of 24 indicating no perceived functional limitations). They additionally completed a battery of functional fitness assessments, which included HGS, 30-s Chair Stand, 8-ft Up-and-Go, 10 lb and 25 lb lift and carry, and 400 m Walk Test. A self-developed cell phone application was utilized to produce more outcomes, such as steady-state gait speed and cadence during the 400 m Walk Test. Independent samples t-tests were used to compare the perceived and actual functional fitness outcomes between subjects with grip strength <30 kg and those with grip strength ≥30 kg. Additionally, positive predictive value (PPV) and negative predictive value (NPV) were calculated to investigate the accuracy of a 30 kg HGS cutoff to identify subjects with perceived functional limitations (indicated by a CPF Scale score <24) or actual functional limitations (indicated by scoring below 2 standard deviations from the mean of the reference group, subjects with HGS ≥30 kg). Results: Subjects with a HGS ≥30 kg scored significantly higher on the CPF Scale, compared with subjects with a HGS <30 kg (23.9+/-vs. 22.4+/-3.3, respectively). Likewise, subjects with a HGS ≥30 kg performed significantly better on every functional fitness test outcome, compared with subjects with a HGS <30 kg. The NPV (true negative) was excellent (≥90%) for all outcomes, while the PPV (true positive) was poor (≤ 56%) for all outcomes. Conclusions: A HGS ≥ 30 kg appears to be an appropriate cutoff to accurately rule out current functional limitations in males and females 40 years of age and older, but it is not suitable to accurately identify individuals with current functional limitations. It is suggested that individuals with a HGS <3...

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Background: Our lab previously demonstrated that the manual assessment (with a cell phone stopwatch) of the 30-s Chair Stand, 8-ft Up-and-Go, and 6 Minute Walk Test was as or more valid and reliable than using body-worn sensors. Based on this finding, we developed an Android cell phone application (App) to improve the feasibility of data collection and to automatically calculate outcomes. The main purpose of the present study was to validate the App against slow-motion video analysis for the assessment of outcomes from the 30-s Chair Stand, 8-ft Up-and-Go, and 400 m Walk Test. Methods: A subset of 15 subjects were randomly selected from our larger Steps Taken Against Neuromuscular Decline (STAND) Initiative cohort for this validity assessment. Each subject completed a single trial of the 30-s Chair Stand, 8-ft Up-and-Go, and 400 m Walk Test (in that order). One investigator assessed the subject using the App, while another filmed the test at 240 frames per second. The videos were played back frame-by-frame to manually timestamp the same events that were timestamped live using the App. The mean difference between the App and video (bias) was assessed with paired t-tests, and 95% Limits of Agreement were established to represent the random error between the two measures. Results: No significant bias between the App and slow-motion video was detected for any 30-s Chair Stand or 400 m Walk Test outcome, or for the total time taken to complete the 8-ft Up-and-Go. Paired t-tests did, however, suggest a numerically small but systematic negative bias for all other 8-ft Up-and-Go outcomes, indicating that subcomponents of the 8-ft Up-and-Go are slightly faster when being assessed by the App, compared with slow-motion video. The 95% Limits of Agreement were most narrow for the 30-s Chair Stand and 400 m Walk Test components, as well as total time on the 8-ft Up-and-Go, with a broader limits for other 8-ft Up-and-Go components. Conclusions: The App validly assessed all 30-s Chair Stand and 400 m Walk Test outcomes, as well as the total time taken to complete the 8-ft Up-and-Go. Given that the App is as or more valid than existing technologies, with respect to the outcomes it reports, its greater feasibility may make it an appropriate addition to clinical and fitness settings.