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The role of M. popliteus in unpredictable and in self-initiated balance provocations.
Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.ORCID iD: 0000-0002-0366-4609
2006 (English)In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 24, no 3, 524-530 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study was to determine whether m. popliteus (POP) activity would contribute to the control of knee joint position in unpredictable and in self-initiated provocations of standing balance. Ten healthy women (age 25.2 +/- 4.5 years, means and SD) without known knee pathology were tested for postural reactions (1) to unpredictable support surface translations in anterior and posterior directions, and (2) in self-initiated balance provocations in a reaction time (RT) forward reach-and-grip task. Electromyographic activity was recorded from POP and other leg muscles plus the deltoid muscle. Three-dimensional kinematics were captured for the knee joint and the body centre of mass was calculated. POP was active first of all the muscles recorded, regardless of translation direction, and knee joint movements elicited were either knee extension or external rotation of the tibia. In the RT task, the POP was active after initiation of reaching movement, and there was little consistency in the kinematic response. POP activity was not direction specific in response to support surface translation, but appeared triggered from reactive knee joint movement. The response to the support-surface translation suggests that POP served to control knee joint position rather than posture. In the RT task, we could not deduce whether POP activity was attributed to knee joint control or to postural control. Copyright 2006 Orthopaedic Research Society.

Place, publisher, year, edition, pages
2006. Vol. 24, no 3, 524-530 p.
Keyword [en]
Adult, Biomechanics, Electromyography, Female, Humans, Knee Joint/*physiology, Motor Activity, Muscle; Skeletal/*physiology, Musculoskeletal Equilibrium/*physiology
Research subject
URN: urn:nbn:se:umu:diva-14304DOI: 10.1002/jor.20057PubMedID: 16456827OAI: diva2:153975
Available from: 2008-01-03 Created: 2008-01-03 Last updated: 2015-01-21Bibliographically approved
In thesis
1. Motor control of the knee: kinematic and EMG studies of healthy individuals and people with patellofemoral pain
Open this publication in new window or tab >>Motor control of the knee: kinematic and EMG studies of healthy individuals and people with patellofemoral pain
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Patellofemoral pain (PFP) is believed to be associated with deficits in coordination between the different heads of the quadriceps muscle; however, considerable debate exists in the literature regarding the presence of such a deficit. Discrepancies between studies may be explained by differences in experimental tasks, such as whether the task is performed with open (OKC) or closed kinetic chain (CKC), or whether the activity is voluntary or triggered. Particular interest has been directed toward the function of the vastus medialis obliquus (VMO), which is a short muscle with limited ability to exert torque across the knee joint, but probably has a particular role in controlling patellofemoral joint position. Another short muscle that may influence knee joint position control is popliteus (POP), which is located in the back of the knee.

This thesis investigates task specific activity of quadriceps in CKC versus OKC and studies the relative activity between the four heads of the quadriceps in PFP subjects compared to controls without knee pain in voluntary activity (CKC and OKC) and postural responses to balance perturbations. In addition, this thesis investigates the presumed function of POP for control of joint position in postural tasks in healthy individuals.

All subjects were of normal weight and height and between 18 and 40 years. Quadriceps activity was tested for isometric with identical joint configuration in CKC and OKC, and it was performed as a reaction time task. Balance perturbations were elicited by unpredictable anterior and posterior translations of the support surface. Function of POP was investigated in unpredictable support surface translations and in self induced provocations to balance by moving the arms. Muscle activity was recorded with electromyography (EMG). Optic kinematic analysis was used to obtain specific movement responses to perturbations of balance.

The quadriceps muscles were activated differently in CKC and OKC. VMO was activated earlier and to a greater degree in CKC. Rectus femoris was activated earlier and to a greater degree in OKC. PFP subjects reacted slower in both CKC and OKC, but there was no difference between groups in the relative activity between the different heads of the quadriceps. In the unpredictable support surface translation in the anterior direction, PFP subjects responded with earlier onset of VMO and with greater trunk and hip flexion in the anterior translation. POP activation in response to support surface translations in both directions occurred before all other muscles measured. In the self-initiated provocations of balance, POP was activated after the initiation of the balance provocation.

This thesis concludes that quadriceps activity was task specific. The lack of difference between groups in OKC and CKC, and the difference between groups in postural responses suggest that variations in motor behaviour may occur only in tasks habitually performed. Differences in muscle activation patterns may be related to compensatory strategies to unload the quadriceps muscles and the patellofemoral joint. Furthermore, this thesis suggests that POP muscle may have a particular role in active control of the knee joint.

Place, publisher, year, edition, pages
Umeå: Samhällsmedicin och rehabilitering, 2005. 90 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 987
Kinematics; Kinetic chain tasks; Knee; Motor Control; Muscle activity; Patellofemoral pain; Unpredictable perturbations
National Category
urn:nbn:se:umu:diva-644 (URN)91-7305-951-X (ISBN)
Public defence
2005-12-16, Aulan, Vårdvetarhuset, Umeå Universitet, Umeå, 09:00 (English)
Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2015-01-21Bibliographically approved

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