Static pre-load effect on knee extensor isokinetic concentric and eccentric performance

Jensen, Reece C.; Warren, Bryan F.; Laursen, Carlton; Morrissey, Matthew C.

doi:10.1249/00005768-199101000-00003

Cited by 43 publications

(42 citation statements)

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“…Across all strength evaluations (20 subjects, three joints, two limbs, two directions), the preload was a mean of 66%±17 of the peak torque value. Optimum preload values have not been established in the literature, however, the preloads used in this study were similar in magnitude to the high preload conditions used by Kramer et al 43 and a Chattanooga Group Inc., TN Jensen et al 44 Their high preload conditions were equivalent to 70 to 75% of the peak torque values and were found to increase average torque over lower preload conditions. Participants were asked to "push or pull as hard as possible" throughout their available range of motion for a minimum of four repetitions or until consistency of the force-angle profile (i.e., pattern) was found across three repetitions (the maximum number of repetitions experienced by any one subject was six).…”

Section: Test Protocolsupporting

confidence: 53%

“…43,44 The preload was individualized 45 for each subject, joint and direction of motion and was set at a minimum of 50% of the peak torque values observed during the warm-up trials and kept constant across the two test sessions. Across all strength evaluations (20 subjects, three joints, two limbs, two directions), the preload was a mean of 66%±17 of the peak torque value.…”

Section: Test Protocolmentioning

confidence: 99%

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Reliability of lower extremity strength measures in persons with chronic stroke

Eng

Kim

MacIntyre

2002

Archives of Physical Medicine and Rehabilitation

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Objective-To determine the reliability of isokinetic concentric strength measures of both the hemiparetic and non-involved limbs for flexion and extension motions of the hip, knee, and ankle joints in individuals who have had a stroke.Design-Test-retest, repeated-measures intraobserver reliability design. Setting-Tertiary rehabilitation center.Participants-20 community-dwelling individuals who have had a stroke, with motor deficits ranging from 3 to 6 on the Chedoke-McMaster Stroke Assessment; volunteer sample. Interventions-Not applicable.Main Outcome Measures-Peak torque and average torque (ie, mean over the range of motion tested) from an ensemble-averaged (three trials) torque-angle curve during isokinetic concentric extension and flexion movements of the ankle, knee, and hip.Results-Although peak and average torque were significantly less for the hemiparetic limb compared with the non-involved limb, the intraclass correlation coefficients (ICCs) between the two test sessions were high (0.95-0.99 for peak torque, 0.88-0.98 for average torque) for both limbs for all 3 joints. However, there was a learning effect, as observed by the slightly greater values attained from the second test session.Conclusions-Peak and average isokinetic torque can be used to assess reliably lower extremity strength in persons with chronic stroke. Practice sessions may be required before the actual test to reduce the effect of learning.

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Section: Test Protocolsupporting

confidence: 53%

Section: Test Protocolmentioning

confidence: 99%

Reliability of lower extremity strength measures in persons with chronic stroke

Eng

Kim

MacIntyre

2002

Archives of Physical Medicine and Rehabilitation

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“…This appears to be intuitively obvious because the use of preload deletes the lower torques used at the beginning of the range, thereby increasing the average torque. It has also been reported that implementing a preload appears to have no effect on peak torque values (Jensen et al 1991;Kramer et al 1991;Laurie et al 1993;Narici et al 1991).…”

Section: Introductionmentioning

confidence: 97%

“…Average torque has been defined as the average of torque measurements over the selected range of motion. Several authors have reported that increasing the preload results in greater average torques (Jensen et al 1991;Kramer et al 1991;Laurie et al 1993). This appears to be intuitively obvious because the use of preload deletes the lower torques used at the beginning of the range, thereby increasing the average torque.…”

Section: Introductionmentioning

confidence: 99%

“…The possibility existed that a view of the effect of preload on variability in average torques might be confounded by the interacting effect of force magnitude on variability. On the other hand, it has been reported that peak torque magnitude is unaffected by preload (Jensen et al 1991;Kramer et al 1991;Laurie et al 1993;Narici et al 1991). We therefore selected to study peak, rather than average torque measurements.…”

Section: Introductionmentioning

confidence: 99%

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The effect of preload on variability in dynamometric measurements of knee extension

Morton

Keating

2002

Eur J Appl Physiol

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The unwanted variability in dynamometric measurements limits accurate interpretation of these measurements. Although unpredictable variability in measurements has been identified repeatedly, few studies have investigated strategies for reducing measurement error. This study investigated the effect of preload on variability in dynamometry. Preload is the force that must be overcome before the lever arm begins to move at a preset speed. On the basis of related research, it was hypothesised that under higher preloads, subjects would perform more consistently. Twenty subjects (ten male and ten female), aged 19-24 years, performed repeated right concentric knee extension tests. Using the Kin-Com dynamometer and a lever arm speed of 60 degrees x s(-1), extension torques were recorded for each subject under four different preload conditions. Preloads were 5%, 25%, 45% and 65% of the torque achieved during each subject's maximal voluntary contraction (MVC). Each subject performed six test repetitions under each preload. Variability in peak torque was significantly smaller under the 65% preload compared to the 5% preload. In addition, the regression of preload against group mean variability indicated that as preload increased, the variability in peak torque decreased in a highly predictable way. The results from this study suggest that subjects perform more consistently under conditions of higher preload than under lower preloads. By adopting higher preloads for dynamometry testing, measurement accuracy and the potential clinical utility of measurements is improved.

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