Voluntary Activation During Isokinetic Contractions in Subjects With Neuromotor Disorders

Study Overview
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Brief Summary
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Activation is the amount of voluntary recruitment of a muscle during voluntary contraction. Full activation implies the recruitment of all muscle fibres at their tetanic frequency. In healthy subjects, and even in sports performances, full activation may be rarely achieved despite a subjectively maximal effort. Highly decreased activation has been observed in patients affected by various orthopaedic and neurological disorders. In these subjects, paresis may be caused or aggravated by primitive impairments of the central nervous system and/or, by stimuli arising from peripheral damaged tissues that inhibit the corticospinal or the intraspinal recruitment of motoneurones (arthrogenous muscle weakness). There are numerous investigations in the literature on activation measured during isometric contractions, while they are substantially missing as far as isokinetic concentric contractions are concerned. There are reasons to suppose that, contrary to what has been demonstrated for healthy subjects, in patients with various motor impairments the activation is diminished the more, the higher is the joint rotation speed. The present study aims to investigate the amount of activation of the quadriceps femoris during subjectively maximal isometric contractions at 40° knee flexion (0°=complete extension) and isokinetic concentric contractions at an angular velocity of 100°/s in patients with various orthopaedic and neurologic conditions. Activation will be measured on an isokinetic dynamometer, through the interpolated twitch technique. This consists of stimulating a representative sample of the muscle belly through an electric shock. If the shock does not generate an extra force during contraction, all muscle fibres belonging to the sample reached by the electric shock can be claimed to be recruited at their tetanic frequency. Otherwise, following the stimulus, a twitch can be observed revealing submaximal voluntary recruitment of the muscle.

Official Title
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Measuring Voluntary Activation of the Quadriceps Femoris During Isokinetic Concentric Contractions With the Interpolated Twitch Technique (ITT) in Subjects With Neuromotor Disorders

Conditions
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Multiple Sclerosis, Poststroke/CVA Hemiparesis, Parkinson Disease, Knee Impairment

Intervention / Treatment
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* Other: Pathologic group


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age between 18 and 70 years old; ability to sign the informed consent form; ability to understand the instructions and to complete the motor task; voluntary knee flexion-extension range of at least 70°; maximal extension of angle < 30° (0°=full extension, 180° sagittal tibio-femural angle). Exclusion Criteria: pregnancy; a history of epilepsy (to avoid the risk for seizures triggered by the stimuli); Mini Mental State Examination ≤27/30; implanted electro-sensitive devices; any orthopedic condition limiting the articular mobility or muscular strength of the lower limbs; current treatment with oral anticoagulant therapy (to avoid the risk for muscle hemorrhage); medium/serius osteoporosis (femoral Bone Mineral Density on the affected side, t-score < (-3.5)); familiarity with the testing method.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Pathologic group<br>At least 20 participants with various neurologic or orthopaedic conditions (for example, hemiparesis post-stroke, multiple sclerosis, traumatic knee injuries, knee osteoarthritis) will be enrolled. | Other: Pathologic group<br>* Voluntary Activation level will be determined according to the interpolate twitch technique (ITT). During isometric contractions (knee at 40° flexion), three electric shocks (doublets) will be delivered. The first shock will be delivered at rest before contraction. The second one will be delivered 3-4 s after the beginning of the effort. The third one will be delivered at rest 2-3 s after the contraction has ended. Two isometric contractions will be performed, with a 3-minute break. Then, 3 consecutive continuous passive motion (CPM) extension-flexions of the knee joint (range 105-0°), and 3 isokinetic concentric contractions (ISOK) will be performed. During both CPM and ISOK an electric shock will be delivered during each repetition. The instant of stimulation will be determined in a way allowing the twitch moments to peak at exactly 40° of knee flexion during extension. The same procedure will be administered first to the affected limb, and then to the non-affected limb.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Voluntary Activation | Voluntary Activation = [1 - (Interpolated Twitch/Resting Twitch)]%, where Interpolated Twitch and Resting Twitch are the peak torques caused by the electric shock during the voluntary contraction and a rest, respectively | Day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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voluntary activation, rehabilitation, lower limb, interpolated twitch technique