Biomedical subjects

Summer B Cook

Publications and source records attributed to Summer B Cook.

4 recordsLinked to original sources

PubMed2006

Reliability of techniques to assess human neuromuscular function in vivo.

The purpose of this study was to comprehensively evaluate the reliability of a large number of commonly utilized experimental tests of in vivo human neuromuscular function separated by 4-weeks. Numerous electrophysiological parameters (i.e., voluntary and evoked electromyogram [EMG] signals), contractile properties (i.e., evoked forces and rates of force development and relaxation), muscle morphology (i.e., MRI-derived cross-sectional area [CSA]) and performance tasks (i.e., steadiness and time to task failure) were assessed from the plantarflexor muscle group in 17 subjects before and following 4-weeks where they maintained their normal lifestyle. The reliability of the measured variables had wide-ranging levels of consistency, with coefficient of variations (CV) ranging from approximately 2% to 20%, and intraclass correlation coefficients (ICC) between 0.53 and 0.99. Overall, we observed moderate to high-levels of reliability in the vast majority of the variables we assessed (24 out of the 29 had ICC>0.70 and CV<15%). The variables demonstrating the highest reliability were: CSA (ICC=0.93-0.98), strength (ICC=0.97), an index of nerve conduction velocity (ICC=0.95), and H-reflex amplitude (ICC=0.93). Conversely, the variables demonstrating the lowest reliability were: the amplitude of voluntary EMG signal (ICC=0.53-0.88), and the time to task failure of a sustained submaximal contraction (ICC=0.64). Additionally, relatively little systematic bias (calculated through the limits of agreement) was observed in these measures over the repeat sessions. In conclusion, while the reliability differed between the various measures, in general it was rather high even when the testing sessions are separated by a relatively long duration of time.

Adult↗

PubMed2006

Evaluating task modification as an objective measure of functional limitation: repeatability and comparability.

BACKGROUND: Modification of everyday tasks in older adults is associated with risk of deleterious health outcomes. The purpose of this study was to develop a task modification scale to examine its reliability and comparability to timed performance and common measures of physical function and impairment. METHODS: Eighty-two (21 men, 61 women) older adults (74.4 +/- 8.2 years) were observed performing a chair rise (sitting heights: 43 cm, 38 cm, and 30 cm), stair ascent/descent, and kneel and supine rise tasks. Six hierarchically ranked categories (0-5) of modification were created for each task and then summed across tasks (summary modification [MOD] score: range 0-35). Comparisons were made with timed performance, knee extension strength, single-leg balance, self-reported function, five chair stands, and gait speed. RESULTS: Inter-rater reliability (intra-class correlation = 0.98) and participant repeatability (intra-class correlation = 0.92) of the MOD score were excellent. Ninety-six percent of participants modified at least one task (MOD score: 10.5 +/- 7.51, range 0-27). After adjusting for task modification, timed performance showed a lower association with gait speed (time vs MOD score, semipartial r2 = 0.31 vs 0.68), strength (semipartial r2 = 0.14 vs 0.65), and single-leg balance (semipartial r2 = 0.10 vs 0.40) than did the MOD score. The MOD score showed higher correlations with muscle strength and balance impairment than did other measures of functional limitation such as gait speed, time to complete five chair stands, and self-reported physical function. CONCLUSION: Documentation of task modification is reliable across raters and repeatable within participants; in addition, it compares well with other measures of physical function and impairment. Task modification reveals important and intuitive information regarding physical limitation, and deserves greater attention.

Activities of Daily Living↗

PubMed2006

Accelerometry as a measure of subject compliance in unilateral lower limb suspension.

INTRODUCTION: Human unilateral lower limb suspension (ULLS) is a commonly used model to study the effects of disuse and unweighting of human skeletal muscle. ULLS requires subjects to ambulate on crutches with an elevated shoe on the weight-bearing limb or a strap on the unloaded limb for prolonged periods of time (i.e., 4-5 wk). Ensuring compliance during ULLS participation is critical to the integrity of the study. PURPOSE: The purpose of this study was to determine the accuracy of an accelerometer to detect steps taken while walking and to measure the effectiveness of an accelerometer to monitor compliance during ULLS. METHODS: There were 10 subjects (26.2 +/- 3.6 yr; 170.9 +/- 6.9 cm; 68.0 +/- 9.6 kg) who participated in two conditions: normal walking and ULLS (left leg was unweighted via an elevated shoe on the contralateral limb) at various speeds. Additionally, subjects completed an obstacle course to simulate daily activities. During these activities, subjects wore a planar accelerometer on their left ankle to measure acceleration. The mean peak axial acceleration (MPAA) of the leg in the swing phase of walking was determined by the accelerometer and a step was detected during ULLS if the MPAA was greater than or equal to the minimum MPAA observed during walking. From this, the sensitivity of the accelerometer was determined. During ULLS, the number of steps detected by the accelerometer with an MPAA--the minimum MPAA during walking was computed and the specificity of the accelerometer was determined. RESULTS: The sensitivity of the accelerometer during walking was 96% and the specificity during ULLS was 97%. CONCLUSION: An accelerometer is an accurate tool to quantify the number of steps taken during walking and it may be used to measure subject compliance during ULLS.

Acceleration↗

PubMed2005

Knee extensor isometric unsteadiness does not predict functional limitation in older adults.

OBJECTIVE: To determine how knee extensor steadiness is related to age and difficulty performing everyday tasks. DESIGN: In this cross-sectional study performed at a research laboratory, 50 older adults (age range, (56-95 yrs) performed steadiness testing at 50% of maximum strength and were timed and rated on four tasks of daily living: chair rise, stair ascent and descent, and walk. The independent variables of age, steadiness, and strength-to-weight ratio were entered into regression models with the ratings and time to complete the four everyday tasks as dependent variables. RESULTS: The strength-to-weight ratio was the only significant predictor in the multiple regression models, explaining 29%, 33%, 14%, and 14% of the variance in gait speed and time to complete a chair rise, stair ascent, and stair descent, respectively. Similar results were seen with task ratings. Age was not correlated with steadiness (r = 0.25, P = 0.07). CONCLUSION: This study suggests that knee extensor isometric steadiness performance does not carry over to tasks of everyday living, and older subjects, regardless of age, have similar steadiness values. Because the strength-to-weight ratio predicted the most variance in functional performance, it is recommended that muscle strength be improved to increase function in older adults.

Activities of Daily Living↗