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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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EFFECTS OF FATIGUE ON FRONTAL PLANE KNEE MOTION, MUSCLE ACTIVITY, AND GROUND REACTION FORCES IN MEN AND WOMEN DURING LANDING |
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Michael P. Smith  ,
Phillip S. Sizer and C. Roger James |
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Texas Tech University Health Sciences Center, Center for Rehabilitation Research, Lubbock, Texas, USA |
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© Journal of Sports Science and Medicine (2009) 8, 419 - 427 |
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| ABSTRACT | |||
| Women tear their Anterior Cruciate Ligament (ACL) 2-8 times more
frequently than men. Frontal plane knee motion can produce a pathological
load in the ACL. During a state of fatigue the muscles surrounding the knee
joint may lose the ability to protect the joint during sudden deceleration
while landing. The purpose of this study was to investigate the effects
of fatigue and gender on frontal plane knee motion, EMG amplitudes, and
GRF magnitudes during drop- jump landing. Pretest-posttest comparison group
design was used. Twenty-six volunteers (14 women; 12 Men; Mean ± standard
deviation age = 24.5 ± 2.7 yrs; height = 1.73 ± 0.09 m; mass = 74.3 ± 11.8
kg) participated in the study. Knee frontal plane ranges of motion and positions,
ground reaction force peak magnitudes, and surface EMG RMS amplitudes from
five lower extremity muscles (vastus medialis, vastus lateralis, medial
hamstring, lateral hamstring, and lateral gastrocnemius) were obtained during
the landing phase of a drop-jump. MANOVA and ANOVA indicated that peak GRF
significantly (p < 0.05; 2.50 ± 0.75 BW vs. 2.06 ± 0.93 BW) decreased
during fatigued landings. No other variables exhibited a fatigue main effect,
although there was a significant (p < 0.05) fatigue by gender interaction
for the frontal plane range of motion from initial contact to max knee flexion
variable. Follow-up analyses failed to reveal significant gender differences
at the different levels of fatigue for this variable. Additionally, no variables
exhibited a significant gender main effect. Single subject analysis indicated
that fatigue significantly altered frontal plane knee motion, peak GRF,
and EMG in some subjects and the direction of differences varied by individual.
Fatigue altered some aspects of landing performance in both men and women,
but there were no gender differences. Additionally, both group and single
subject analyses provided valuable but different information about factors
representing neuromuscular control during drop-jump landing.
Key words: ACL, injury, gender differences, drop-jump landing. |
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