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Muscle activation and torque generat...

McNutt, Jennifer Suzanne.

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Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis./
Author:	McNutt, Jennifer Suzanne.
Description:	109 p.
Notes:	Source: Masters Abstracts International, Volume: 45-03, page: 1558.
Contained By:	Masters Abstracts International45-03.
Subject:	Biology, Physiology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=MR20528
ISBN:	9780494205280

Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis.
McNutt, Jennifer Suzanne.

Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis. - 109 p.

Source: Masters Abstracts International, Volume: 45-03, page: 1558.

Thesis (M.A.Sc.)--Dalhousie University (Canada), 2006.

Muscle activation and maximal torque generation has been thought to be impaired in knee osteoarthritis (OA). Deficits in muscle activation and maximal torque generation have yet to be clearly established in the early stage of the OA disease process. There is a need to understand what deficits in muscle activation and knee torque generation exist in those with early-stage knee OA so that appropriate interventions such as therapeutic exercise can be prescribed. The purpose of this study was to determine if muscle activation and torque generating capabilities of the knee extensor (KE) and knee flexor (KF) musculature differ between subjects with moderate knee OA and asymptomatic controls (CON) during maximal voluntary isometric contractions (MVIC). Twenty patients with moderate knee OA and twenty participants with healthy knees were matched for BMI and sex. Anterior-posterior standard radiographs were available for the twenty OA subjects. Both groups completed the WOMAC Osteoarthritis Index. Surface electromyography (EMG) was collected from silver/silver chloride electrodes placed over the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), lateral (LH) and medial hamstrings (MH) and lateral (LG) and medial gastrocnemius (MG) muscles of the affected limb for the OA subjects and a random leg for the controls. The EMG signals from each muscle were amplified (AMTI-8, Bortec, Canada) and digitized at 1000 Hz using the Optotrak motion analysis system and processed using Matlab(TM) software. A series of eight three second MVIC targeting specific muscles were used to elicit maximum muscle activation from the seven muscles. The 0.1 second maximal raw root-mean-square (RMS) EMG amplitudes per muscle was the dependent variable analyzed to determine whether differences existed between groups and among muscles for the maximum activity generated. Maximum knee extension (KE) and flexion (KF) torques were measured using a Cybex II dynamometer at two positions (KE 45° and 15° and KF 55° and 15°) and were used to test for strength differences between groups and whether position affected strength. For each muscle, the 0.5 second window of linear enveloped (LE) EMG matched to the maximum torque was normalized to that muscle's maximum LE EMG amplitude obtained from the MVIC tasks. Analysis of variance models were used to test for differences in maximal RMS EMG amplitudes between groups and muscles, differences in KE and KF maximal torques between groups and positions and differences in the maximal torque matched normalized LE EMG amplitudes between groups, muscles and positions for the KE and KF MVIC. There were no significant differences in maximal RMS EMG amplitudes between groups. The CON group produced significantly (p < 0.05) higher torques for KE at 45° and KF at both 55° and 15°. No group differences in normalized LE EMG amplitudes were found for the KE exercises; however for KF exercises, the OA group activated the medial hamstrings and the two gastrocnemius muscles to lower percentages of maximum compared to the CON group. Antagonist muscles were activated to less than 12% of their maximum amplitude by both groups for all exercises. This is the first study to combine maximal torque with EMG data in early-stage knee OA. These findings highlight the need to consider agonist, antagonist and synergist muscle activation when assessing knee muscle function and developing therapeutic interventions in knee OA.

ISBN: 9780494205280Subjects--Topical Terms:

1017816
Biology, Physiology.

Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis.
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245 1 0 $a Muscle activation and torque generating capabilities at the knee joint in moderate knee osteoarthritis.
300 $a 109 p.
500 $a Source: Masters Abstracts International, Volume: 45-03, page: 1558.
502 $a Thesis (M.A.Sc.)--Dalhousie University (Canada), 2006.
520 $a Muscle activation and maximal torque generation has been thought to be impaired in knee osteoarthritis (OA). Deficits in muscle activation and maximal torque generation have yet to be clearly established in the early stage of the OA disease process. There is a need to understand what deficits in muscle activation and knee torque generation exist in those with early-stage knee OA so that appropriate interventions such as therapeutic exercise can be prescribed. The purpose of this study was to determine if muscle activation and torque generating capabilities of the knee extensor (KE) and knee flexor (KF) musculature differ between subjects with moderate knee OA and asymptomatic controls (CON) during maximal voluntary isometric contractions (MVIC). Twenty patients with moderate knee OA and twenty participants with healthy knees were matched for BMI and sex. Anterior-posterior standard radiographs were available for the twenty OA subjects. Both groups completed the WOMAC Osteoarthritis Index. Surface electromyography (EMG) was collected from silver/silver chloride electrodes placed over the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), lateral (LH) and medial hamstrings (MH) and lateral (LG) and medial gastrocnemius (MG) muscles of the affected limb for the OA subjects and a random leg for the controls. The EMG signals from each muscle were amplified (AMTI-8, Bortec, Canada) and digitized at 1000 Hz using the Optotrak motion analysis system and processed using Matlab(TM) software. A series of eight three second MVIC targeting specific muscles were used to elicit maximum muscle activation from the seven muscles. The 0.1 second maximal raw root-mean-square (RMS) EMG amplitudes per muscle was the dependent variable analyzed to determine whether differences existed between groups and among muscles for the maximum activity generated. Maximum knee extension (KE) and flexion (KF) torques were measured using a Cybex II dynamometer at two positions (KE 45° and 15° and KF 55° and 15°) and were used to test for strength differences between groups and whether position affected strength. For each muscle, the 0.5 second window of linear enveloped (LE) EMG matched to the maximum torque was normalized to that muscle's maximum LE EMG amplitude obtained from the MVIC tasks. Analysis of variance models were used to test for differences in maximal RMS EMG amplitudes between groups and muscles, differences in KE and KF maximal torques between groups and positions and differences in the maximal torque matched normalized LE EMG amplitudes between groups, muscles and positions for the KE and KF MVIC. There were no significant differences in maximal RMS EMG amplitudes between groups. The CON group produced significantly (p < 0.05) higher torques for KE at 45° and KF at both 55° and 15°. No group differences in normalized LE EMG amplitudes were found for the KE exercises; however for KF exercises, the OA group activated the medial hamstrings and the two gastrocnemius muscles to lower percentages of maximum compared to the CON group. Antagonist muscles were activated to less than 12% of their maximum amplitude by both groups for all exercises. This is the first study to combine maximal torque with EMG data in early-stage knee OA. These findings highlight the need to consider agonist, antagonist and synergist muscle activation when assessing knee muscle function and developing therapeutic interventions in knee OA.
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