Test-retest reliability of knee extensor rate of velocity and power development in older adults using the isotonic mode on a Biodex System 3 dynamometer

Abstract

Isotonic testing and measures of rapid power production are emerging as functionally relevant test methods for detection of muscle aging. Our objective was to assess reliability of rapid velocity and power measures in older adults using the isotonic mode of an isokinetic dynamometer. Sixty-three participants (aged 65 to 82 years) underwent a test-retest protocol with one week time interval. Isotonic knee extension tests were performed at four different loads: 0%, 25%, 50% and 75% of maximal isometric strength. Peak velocity (pV) and power (pP) were determined as the highest values of the velocity and power curve. Rate of velocity (RVD) and power development (RPD) were calculated as the linear slopes of the velocity- and power-time curve. Relative and absolute measures of test-retest reliability were analyzed using intraclass correlation coefficients (ICC), standard error of measurement (SEM) and Bland-Altman analyses. Overall, reliability was high for pV, pP, RVD and RPD at 0%, 25% and 50% load (ICC: .85 - .98, SEM: 3% - 10%). A trend for increased reliability at lower loads seemed apparent. The tests at 75% load led to range of motion failure and should be avoided. In addition, results demonstrated that caution is advised when interpreting early phase results (first 50ms). To conclude, our results support the use of the isotonic mode of an isokinetic dynamometer for testing rapid power and velocity characteristics in older adults, which is of high clinical relevance given that these muscle characteristics are emerging as the primary outcomes for preventive and rehabilitative interventions in aging research.

Bench stepping with incremental heights improves muscle volume, strength and functional performance in older women

“…Additionally, the rate of velocity development (RVD in°/s 2 ) at each resistance was calculated (Van Driessche et al, 2018b). Test-retest reliability in our lab shows an ICC ranging from 0.94 to 0.97 and CV% of 7.8 for the isometric tests (Van Roie et al, 2017;Van Driessche et al, 2018a). Reliability for pP, pV and RVD obtained from isotonic tests was also excellent with an ICC ranging from 0.85 to 0.98 for and CV% ranging from 3 to 9 (Van Driessche et al, 2018b).…”

“…Torque and velocity of the knee extensors were obtained using a Biodex System 4 Pro® isokinetic dynamometer (Biodex Medical Systems, Shirley, USA; Fig. 1), in accordance with procedures used in previous studies (Van Roie et al, 2011;Van Driessche et al, 2018a).…”

Reliability of Lower Extremity Muscle Power and Functional Performance in Healthy, Older Women

“…Sample size estimation was made using a web-based sample size calculator ( https://wnarifin.github.io/ssc/ssicc.html ) and methods from Walter et al [ 14 ]. A previous reliability study testing muscle power in older adults [ 9 ] reported an intraclass correlation coefficient (ICC) of 0.96. Using the minimum acceptable reliability of 0.75 [ 15 ], α = 0.05, 80% power, and two repetitions/raters per participant would require a sample size of at least 10 participants.…”

“…Participants were instructed to perform all contractions “as hard and as fast as possible,” and motivation was provided throughout the trial. Maximal voluntary isometric contraction (MVIC) of the knee extensors (KE) and knee flexors (KF) were measured at a knee angle of 90 degrees [ 9 ]. Each trial consisted of KE MVIC, and a brief rest followed by KF MVIC.…”

“…Analysis of video recordings, in other populations, for the assessment of motor skills performance has been shown to be reliable and comparable to live assessment [ 6 ] and could also be used to assess the reliability of functional performance in older adults. While studies typically report the short-term (≤ 2 weeks) reliability of functional outcomes [ 7 – 9 ], the long-term reliability (>12 weeks) [ 10 ] is needed to consider the potential impact of the typical age-related decline in functional performance in addition to measurement error. Buehring et al investigated the short and long-term (∼3 months) reliability of functional tests in older (70–95 years), community-dwelling adults [ 10 ].…”