The effects of fatigue on landing characteristics in college female and male recreational athletes



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Texas Tech University


The purpose of the first study (Chapter II) was to investigate the effects of fatigue and gender on frontal plane knee motion during drop-jump landing. Additionally, neuromuscular and ground reaction force performance characteristics that are thought to be related to the control of frontal plane knee motion were also investigated. The purpose of the second study (Chapter III) was to examine the relationships between static anatomical structural characteristics and frontal plane knee motion. Alterations in these relationships during fatigue were also investigated.

Design of Chapter II: A two factor mixed repeated measures design was used to evaluate the gender and fatigue effects. Subjects were tested in a pre-fatigue state and then again in a fatigued state. A 2 X 2 mixed design repeated measures multivariate analysis of variance (MANOVA), with gender as the between-subjects factor and fatigue as the within-subjects factor, was performed. Fatigue, gender, and fatigue by gender interaction were tested at á = 0.05. Univariate F-tests of the dependent variables were undertaken to establish where significance was present.

Design of Chapter III: A correlation matrix was constructed to determine the relationship among the dependent variables and between the dependent and independent variables. Following generation of the correlation matrix the two variables that showed the highest positive relationship were used in a linear regression model to determine the predictive value of the variables.

Subjects: Twenty-six (14 women and 12 men) healthy active volunteers of average height and weight, between the ages of 18 and 35 years old, participated in the study.

Measurements for Chapter II: All subjects completed 10 pre-fatigue landings from a 50cm height onto a force platform. The fatigue protocol followed and included repeated bouts of isometric contractions of the quadriceps in the squat position with the knee flexed to 60°. Subjects were deemed adequately fatigued when there force production fell below 50% MVC. Kinematic data was collected for frontal plane knee motion with an electric goniometer. Kinetic data was collected from the force platform on which the subjects landed. Surface EMG was collected from 5 muscles: vastus medialis, vastus lateralis, medial hamstring, lateral hamstring, and lateral gastrocnemius.

Measurements for Chapter III: Four clinical measurements were taken: QA, ND, TFA, FT.

Results Chapter II: The fatigue affect showed significance for the peak ground reaction force (F1,24 = 15.89; p < 0.05). No other variables were significant for a fatigue effect. No variables were significant for a gender effect. A significant interaction between fatigue and gender was found for the following variable: valgus range of motion from contact to maximum knee flexion (F1,24 = 7.35; p < 0.05), all other variables were non-significant.

Results Chapter III: The correlation matrix for the non-fatigue group data revealed a significant relationship between FP30 and TFA (r = 0.39) and a significant positive relationship between FProm30 and TFA (r = 0.33) for the group. The correlation matrix for the fatigue group data revealed a significant positive relationship between FProm30 and TFA (r = 0.35) for the group. The correltation matrix for the men (non-fatigue) revealed a significant positive relationship between; FPmax and QA (r=0.61), FP30 and QA (r=0.55), and FPrommax and QA (r=0.51). During the fatigue condition, however, there were no significant relationships between the variables for the men. The correlation matrix for the women (non-fatigue) revealed a significant positive relationship between FProm30 and TFA (r=0.49). During the fatigue condition there were no significant relationships found for the women. None of the regression models yielded significant results.

Conclusion: The results of this study are inconclusive. Peak ground reaction force significantly decreased with fatigue. This is probably due to altered landing strategies during the fatigued state. Although some clinical measures had significant positive correlations with frontal plane motions, none were found to be predictors of frontal plane motion. More research needs to be done in order to further examine the frontal plane motion variables and to determine the role they play in non-contact ACL injuries.



Gender differences, Injury, Anterior cruciate ligament (ACL), Drop-jump landing