Download emg analysis of lower extremity muscle recruitment patterns during

EMG ANALYSIS OF LOWER EXTREMITY MUSCLE RECRUITMENT PATTERNS DURING OPEN KINETIC CHAIN AND
CLOSED KINETIC CHAIN EXERCISES
+*Kawamura, K (A-the Promotion and Mutual Aid Corporation for Private Schools of Japan)
+*Kibi International University, Okayama, JAPAN. Takahashi city, 716-8508, 81-866-22-9454, Fax: 81-866-22-7560, [email protected]
DISCUSSION: The most remarkable observation of this study was the EMG
activities of rectus femoris.
The CKC knee extension generated
approximately twice as much knee extension torque as OKC knee extension
while CKC knee extension generated approximately half as much rectus
femoris activity as OKC knee extension. This decrease in the IEMG of the
rectus femoris might be due to an antagonistic inhibition induced by the
increase in activities of the antagonistic muscles such as gluteus maximus and
hamstrings. During maximal voluntary effort in CKC knee extension, the
force was directed from hip joint to the center of the foot. This means that the
moment around hip joint was almost zero and knee extension moment was
greatest. These results suggest that there appears to be a mechanism to keep
the hip moment at zero in order to stabilize hip joint and to transfer hip monoarticular muscle forces to knee extension torque. In this situation the biarticular muscles must have performed a very important role without fatigue.
Another remarkable observation of this study was that, during CKC knee
extension, minimal hamstrings EMG activity existed. It was speculated that
joint compressive forces play very important roles in knee stability.
a: OKC knee flex/ext
b: CKC knee extension
Fig. 1: Schematic drawing of testing set up
C K C E xt
O K C E xt
O K C F le x
100%
80%
EMG activ
INTRODUCTION: "Closed kinetic chain" (CKC) exercise has become
popular in the last 10 years for use after anterior cruciate ligament (ACL)
reconstructive surgery. Closed kinetic chain exercises appear to have gained
popularity over more traditionally used open kinetic chain (OKC) exercises
because many clinicians believe that CKC exercises are safer and more
functional[1]. Recently various types of CKC exercise method have been
developed[2]. However, comparison of the EMG activity and fatigue patterns
of lower extremity muscles during OKC and CKC has not been reported.
There is a concern that exercises, if prescribed too soon or aggressively, may
be detrimental to the reconstructed graft due to muscle fatigue. The objective
of this study was to investigate the effects of kinetic chain conditions on the
EMG activities of lower extremities.
MATERIALS AND METHODS: Sixteen healthy young male subjects aged
20 to 22 years (21.4 ± 0.7) were tested.
CYBEX 6000 isokinetic
dynamometer was used to measure open and closed concentric torque
generated by the right lower extremity. After informed consent was received,
each subject was instructed to exert isometric maximal voluntary effort in
both of the following two settings.
OKC knee flexion/extension testing procedures Each subject was seated on a
testing bench with the backrest at vertical position. Standard attachments were
used (Fig. 1-a).
CKC knee extension testing procedures Subjects were positioned supine on a
testing bench with the backrest 30 degrees from horizontal. A custom made
foot plate and load cell were attached to the tip of the dynamometer arm.
Stabilization straps were fastened across the anterior ankle and forefoot. The
lengths of the lever arm were adjusted to the length of the subject's lower leg.
Angle referencing was performed by placing the knee in 60 degrees of flexion
with the dynamometer arm 60 degrees from horizontal. This system was
absolutely closed (Fig. 1-b). The isometric force at right angles to the axis
force generated by the right lower extremity (Fa) was measured by the
CYBEX 6000. The axis force (Fb) was measured by the load cell. The actual
force (F) was calculated from the two component forces (Fa and Fb). Each
subject was instructed to exert maximal isometric voluntary effort in knee
extension.
EMG activity measurement The EMG activity from eight muscles was
monitored simultaneously for each exercise using surface electromyography.
The muscles selected were the gluteus maximus, rectus femoris, vastus
medialis, vastus lateralis, medial hamstring, lateral hamstring, medial
gastrocnemius and the lateral gastrocnemius. EMG signals were full-wave
rectified and integrated (IEMG). IEMG values of lower extremity muscles
were normalized to the greatest IEMG value for each subject.
EMG fatigue analysis The median power frequency (MDPF) during
continuous isometric contraction in each condition was measured. The
muscles selected were the rectus femoris, vastus medialis, vastus lateralis and
the biceps femoris.
RESULTS: The OKC knee extension torque was 191.9 ± 43.9 Nm and knee
flexion torque was 105.5 ± 22.5 Nm. The CKC knee extension torque was
387.9 ± 72.4 Nm and the force was directed from hip joint to the center of the
foot. CKC knee extension generated approximately twice as much hamstrings
and gastrocnemius activity as OKC knee extension. However the results
revealed minimal hamstrings and gastrocnemius activity during CKC knee
extension compared with that of OKC knee flexion. OKC knee extension
produced more quadriceps activities while CKC knee extension produced
gluteus maximus and vasti muscle activities. CKC knee extension generated
approximately half as much rectus femoris activity as OKC knee extension
(Fig. 2).
During continuous isometric contraction the MDPF value of four
muscles were decreased. The change in the frequency content of the EMG
signal indicates that the monitored muscles fatigued. CKC knee extension
produced less rectus femoris muscle fatigue.
60%
40%
20%
0%
GM
RF
VM
VL
MH
LH
MG
LG
GM: gluteus maximus, RF: rectus femoris,VM: vastus medialis,
VL: vastus lateralis, MH: medial hamstring, LH: lateral hamstring,
MG: medial gastrocnemius, LG: lateral gastrocnemius
Fig. 2: EMG activities of the lower extremity
Reference
1) Palmitier RA, An KN, Scott SG et al. Kinetic chain exercise in knee
rehabilitation. Sports Medicine 11: 402-413, 1991.
2) Kawamura K., Isokinetic Open versus Closed Kinetic Chain Strength
Testing and Exercising of the Knee. Trans Ortho Res Soc: 725, 1997.
Poster Session - Muscle and Nerve - Hall E
47th Annual Meeting, Orthopaedic Research Society, February 25 - 28, 2001, San Francisco, California
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