Strength Training to Contraction Failure Increases Voluntary Activation of the Quadriceps Muscle Shortly After Total Knee Arthroplasty: A Cross-sectional Study.
OBJECTIVE
The objective of this study was to investigate voluntary activation of the quadriceps muscle during one set of knee extensions performed until contraction failure in patients shortly after total knee arthroplasty.


METHODS
This was a cross-sectional study of 24 patients with total knee arthroplasty. One set of knee extensions was performed until contraction failure, using a predetermined 10 repetition maximum loading. In the operated leg, electromyographic (EMG) activity of the lateral and medial vastus, semitendinosus, and biceps femoris muscles was recorded during the set. Muscle activity (%EMGmax) and median power frequency of the EMG power spectrum were calculated for each repetition decile (10%-100% contraction failure).


RESULTS
Muscle activity increased significantly over contractions from a mean of 90.0 and 93.6 %EMGmax (lateral vastus and medial vastus, respectively) at 10% contraction failure to 99.3 and 105.5 %EMGmax at 100% contraction failure (P = 0.009 and 0.004). Median power frequency decreased significantly over contractions from a mean of 66.8 and 64.2 Hz (lateral vastus and medial vastus, respectively) at 10% contraction failure to 59.9 and 60.1 Hz at 100% contraction failure (P = 0.0006 and 0.0187).


CONCLUSIONS
In patients shortly after total knee arthroplasty, 10 repetition maximum-loaded knee extensions performed in one set until contraction failure increases voluntary activation of the quadriceps muscle during the set.


RESULTS
Gov-identifier: NCT01713140 to the abstract to increase trial transparency.
From the Physical Medicine & Rehabilitation Research-Copenhagen (PMR-C), Department of Physical Therapy, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark (EKM, TB); Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark (EKM); Lundbeck Foundation Centre for Fast-Track Hip and Knee Arthroplasty, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark (TLJ); Frederiksberg Rehabilitation and Health Centre, Frederiksberg Municipality, Copenhagen, Denmark (TLJ); Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, Odense University Hospital and Institute of Clinical Research, University of Southern Denmark, Odense, Denmark (AH-L); National Research Centre for the Working Environment, Copenhagen, Denmark (LLA); Physical Activity and Human Performance Group, SMI, Department of Health Science and Technology, Aalborg University, Denmark (LLA); Department of Orthopedic Surgery, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark (TB); and Clinical Research Centre, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark (TLJ, TB).
Elin Karin
EK
Mikkelsen
Thomas Linding
TL
Jakobsen
Anders
A
Holsgaard-Larsen
Lars Louis
LL
Andersen
Thomas
T
Bandholm
D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007592:Joint Diseases / Q000503:physiopathology / Q000534:rehabilitation* / Q000601:surgery; D007719:Knee Joint; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D016059:Range of Motion, Articular; D055070:Resistance Training / Q000379:methods*; D016474:Weight-Bearing