Ascertaining maximal voluntary effort production during isokinetic knee strength testing of anterior cruciate ligament-reconstructed patients.

OBJECTIVE: The aim of this study was to assess the performance of prediction rules meant for declaration of efforts as being maximal or not during isokinetic strength testing in a cohort that underwent anterior cruciate ligament reconstruction. DESIGN: Thirty-six individuals performed four sets of six reciprocal concentric knee extension/flexion repetitions at a testing speed of 60 degrees per second through a 60-degree range of motion. The sets consisted of a maximal voluntary effort, two nonmaximal sincere efforts at 50% and 75% of self-perceived maximum, and a set attempting to feign or exaggerate thigh muscle strength deficiencies. Strength curve derived set internal consistency measures, namely, cross-correlation and percent root mean square difference scores, were inputted into the prediction rules, whose performance is reported as specificity and sensitivity percentages. RESULTS: Dependent on the prediction rule used and when expressed on an individual participant basis, the corresponding specificity and sensitivity values ranged from 66.6% to 97.2% and 97.2% to 94.4%, respectively. CONCLUSIONS: Using the prediction rules presented in this investigation, clinicians may be able to ascertain maximal effort production during isokinetic testing in those who have undergone surgical reconstruction of their anterior cruciate ligament.

Reproducibility of isokinetic knee eccentric and concentric strength indices in asymptomatic young adults.

OBJECTIVE: To assess the reproducibility of isokinetic eccentric and concentric knee extension and flexion strength indices obtained at two different angular velocities. DESIGN: Cohort study. SETTING: University human performance laboratory. PARTICIPANTS: 45 healthy physically active young adults (25 males). MAIN OUTCOME MEASURES: A non reciprocal protocol of concentric and eccentric contractions of the knee extensors and flexors was performed at 30 and 120°/s. Strength indices evaluated included peak moment; dynamic control ratios; and the difference between eccentric and concentric ratio at the two angular velocities. RESULTS: No evidence for inter-test bias in any of the strength indices was noted. Measurement precision for peak moment, as quantified using ratio limits of agreement, suggest that scores may be expected to vary up to 15% for the knee extensors in both eccentric and concentric contraction modes. An error of up to 19% was calculated for the peak moment scores of the knee flexors. Intraclass correlation coefficients revealed fairly robust preservation of participants' rank order for the majority of strength indices (>0.85). CONCLUSION: Isokinetic-related indices of knee muscles performance enable an acceptable level of detection of expected changes in muscular strength parameters as a result of planned interventions.

Discriminating between maximal and feigned isokinetic knee musculature performance using waveform similarity measures.

BACKGROUND: Muscle strength test outcomes may aid in determination of impairment or disability rating following injury. In such settings, verification of participant effort during testing is imperative. This investigation explored the utilization of within-set moment waveform similarity measures, namely cross correlation and percent root mean square difference scores, to develop decision rules for discriminating between maximal and feigned efforts during isokinetic testing of the knee joint musculature. METHODS: A mixed-gender sample of 46 participants performed non-reciprocal sets of maximal or feigned knee extension and flexion concentric and eccentric efforts at testing velocities of 30°s(-1) and 120°s(-1). Logistic regression and Monte Carlo simulations were used to derive decision rules for differentiating between the two effort types. FINDINGS: Employing cutoff scores corresponding to 100% specificity; sensitivities of the knee extensor's velocity-specific decision rules were 92.4% and 84.8%, respectively. The velocity-specific knee flexor's test sensitivities were 56.5% and 46.7%. INTERPRETATION: Utilizing the proposed decision rules, substantiating maximal effort performance of the knee extensors may be possible using this specific testing protocol. However, the proposed methods are limited in their ability to verify performance of maximal knee flexor efforts.

Differentiating between types and levels of isokinetic knee musculature efforts.

This investigation assessed whether a measure of moment curve shape similarity, and a measure quantifying curve magnitude differences, enables differentiation between types (sincere vs. feigned) and levels (maximal vs. submaximal) of effort exerted during isokinetic testing of the knee. Healthy participants (n=37) performed four sets of six concentric knee extension-flexion repetitions on two occasions. The sets consisted of: (1) maximal effort; (2) self-perceived 75% of maximal effort; (3) self-perceived 50% of maximal effort; and (4) a set attempting to feign injury. Average cross-correlation and percent root mean square difference values were computed between moment curves in each direction. Logistic regression was used to derive decision rules for differentiating between maximal and submaximal effort levels; and between sincere and feigned effort types. Using a cutoff criteria corresponding to 100% specificity, maximal effort production could be ascertained with 96% sensitivity within the sample. Feigned efforts, however, could be ascertained with only 31% sensitivity due to overlap with sincere submaximal effort. Using the proposed models, clinicians may be able to ascertain whether maximal efforts were produced during isokinetic knee musculature testing. Additionally, evidence regarding participant's intentions with regard to influencing test results may be gauged, although to a lesser extent.