Experimental Study of Strength Training to Activate the Quadriceps Muscle After Total Knee Arthroplasty

Copenhagen University Hospital, Hvidovre20 enrolled

Overview

Background: Progressive strength training is a training modality used in rehabilitation after total knee arthroplasty (TKA). Strength deficits up to 80% in the quadriceps muscle is shown to be present in the operated leg after TKA, which relates to reduced central nervous system (CNS) activation of the muscle. As increased CNS activation occurs during strength training when muscular fatigue is approaching in healthy subjects, it is relevant to investigate if this also is the case after TKA. The clinical implication is that repetitions performed to contraction failure during strength training, may help reduce CNS activation deficits of the quadriceps muscle after TKA. Purpose: The aim of this study is to investigate CNS activation of the quadriceps muscle during strength training performed with repetitions to contraction failure after TKA. Method: Electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST) and biceps femoris (BF) muscles will be recorded during knee extensions performed in a knee extension machine until contraction failure. The relative loading will be 10 repetition maximum (RM). The absolute load (kilograms) corresponding to 10 RM is defined a minimum of 3 days before the day where the EMG-data are recorded. The primary outcomes will be normalized EMG amplitude and median power frequency for each 10th (10%, 20%, 30% failure, etc.) of the set to failure. Hypothesis: Based on previous findings in healthy subjects, we hypothesize that in patients with a TKA, the EMG amplitude will increase while the median power frequency will decrease during a strength training set performed to contraction failure after TKA.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Interventions

1 strength training set performed until contraction failureOTHER

Electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST) and biceps femoris (BF) muscles will be recorded during knee extensions performed in a knee extension machine in a single set performed until contraction failure. The relative loading will be 10 repetition maximum (RM). The absolute load (kilograms) corresponding to 10 RM is defined a minimum of 3 days before the day where the EMG-data are recorded. Range of motion and time under tension for each repetition will be controlled for.

Outcomes

Primary Outcomes

Change from 10% contraction failure in normalized EMG amplitude (%EMGmax).

EMG amplitude-data from the set performed until contraction failure will be reduced to time points corresponding to 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% contraction failure.

Time frame: 10% to 100% contraction failure in a single set performed until contraction failure. The set is performed at a single day, 4 to 8 weeks after surgery.

Change from 10% contraction failure in median power frequency (Hz)

Median power frequency-data from the set performed until contraction failure will be reduced to time points corresponding to 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% contraction failure.

Time frame: 10% to 100% contraction failure in a single set performed until contraction failure. The set is performed at a single day, 4 to 8 weeks after surgery.

Secondary Outcomes

Change from baseline (pre strength training) in Nm/kg body mass

Maximal isometric knee-extension force will be measured, using a fixated hand-held dynamometer, and expressed as the maximal voluntary torque per kilo body mass, using the external lever arm and body weight of each subject.

Time frame: From baseline (pre strength training) to after the set. The set is performed at a single day, 4 to 8 weeks after surgery.

Change from baseline (pre strength training) in knee pain (VAS-mm)

Knee pain is scored by each subject at rest and during strength training, using a standard VAS-ruler with endpoints of "no pain" (0 mm) and "worst pain imaginable" (100 mm).