ACTIVATION PATTERNS OF MONO- AND BI-ARTICULAR MUSCLES IN THE LOWER EXTREMITY AS AN
EXPRESSION OF THE REAL NATURE OF CLOSED KINETIC CHAIN EXERCISE OF THE KNEE
+*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]
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]. But little information is available on the definition of CKC.
This study was conducted upon the hypothesis that the co-activation of the
quadriceps and the hamstrings during CKC exercise is explained by the
coordination of mono- and bi-articular muscles in the lower extremity, with its
activation patterns decided by force direction. The objective of this study was
to assess coordinating functions among antagonistic pairs of the mono- and biarticular muscles in the human lower extremity under CKC conditions by
electromyographic(EMG) kinesiology.
MATERIALS AND METHODS: Eight healthy young male subjects aged
21 to 22 years (21.0±0.5) were tested.
Muscles tested were ; gluteus
maximus(GM) and iliopsoas(IP), vastus medialis(VM) and biceps femoris
short head(BFSH), rectus femolis(RF) and biceps femoris long head(BFLH)
(Fig. I). The CYBEX 6000 isokinetic dynamometer was used. After giving
informed consent, subjects were positioned supine on the testing bench with
the backrest fixed at 15° 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°of flexion with the dynamometer arm
60° from horizontal(Fig. 1). 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. Forces were
normalized to the greatest value for each subject. The EMG activity from six
muscles was recorded during isometric leg press and pull movements in all
directions (360°) around the center of the foot, with maximal effort in the
sagittal plane. EMG data were acquired with surface electrodes on GM, VM,
RF and BFLH, and with fine wire electrodes on IP and BFSH. Those were
integrated and normalized to the greatest IEMG value for each subject. Each
subject was instructed to exert maximal voluntary effort in various directions.
All round force directions were divided into six ranges resulting in three
crossing lines at the foot(Fig. 1). Directions 60°and -120° represented pressing
up and pulling down along the lower leg, and directions 0° and
180°represented pulling up and pushing down, respectively, parallel with the
thigh. Directions 30° and -150° represented the line passing through the hip
joint and the center of foot.
RESULTS: All subjects showed almost the same EMG patterns, whereby the
RF and the BFLH reversed their activity levels in the ranges between 30° and
60 and between -120° and -150°(Fig. 2), the GM and the IP muscle, in the
ranges between 0° and 30° and between -150° and
-180°, and the VM and
the BFSH, in the ranges between 60° and 90° and between -90°and -120°.
Thus, two pairs of the antagonistic mono-articular muscles as well as the pair
of bi-articular muscles showed criss-cross activity patterns in each pair of the
opposing ranges. In the other ranges than the opposing pair of ranges where
the criss-cross patterns appeared, one muscle of the antagonistic pair of monoas well as the bi-articular muscles showed full activity level and the other
antagonist of the pair showed almost nothing.
The pressing force was largest when the force was directed from hip
joint to the center of the foot (30°) (Fig. 3). At this direction only
quadriceps(RF and VM) were activated. Co-activation of quadriceps and
hamstrings were observed in the range between 30° and 60°.
DISCUSSION: Steindler described that a CKC is one in which the terminal
joint meets with some considerable external resistance which prohibits or
restrains its free motion[3]. However he did not describe what considerable
external resistance is nor the participation of force directions. According to
these results, when the maximal pressing force exists in the range between hip
to foot direction and knee to foot direction, co-activation of quadriceps and
hamstrings occur and the force is greatest. By controlling the force direction,
it will be possible to control muscle activation patterns. An understanding of
these results can help in selecting appropriate exercises for knee rehabilitation
and training.
Fig. 1: Schematic drawing showing the testing set up
BFLH
RF
100
50
-180 -150 -120
-90
0
-60 -30
0
30
60
Force Direction (degree)
90
120
150
180
Fig. 2: EMG activities of rectus femoris and biceps femoris long head
100
50
0
-180 -150 -120
-90
-60
-30
0
30
60
90
120
150
180
Force Direction (degree)
Fig. 3: Pressing or pulling forces
REFERENCES: [1] Lutz GE et al, JBJS 75-A:732-739, 1993. [2]
Kawamura K, Trans Ortho Res Soc: 725, 1997. [3]Steindler A, Kinesiology
of the human body under normal and pathological conditions.ed 5: 63-64,
1977.
ACKNOWLEDGMENTS: This work was financially supported by the Science
Research Promotion Fund from the Promotion and Mutual Aid Corporation for
Private Schools of Japan.
Poster Session - Muscle and Nerve - VALENCIA D
46th Annual Meeting, Orthopaedic Research Society, March 12-15, 2000, Orlando, Florida
0831