Graduation date: 2000

Fatigue has been observed to affect lower extremity mechanics during the cutting maneuver. However, there is a lack of research examining the effect of fatigue and limb dominance on lower extremity mechanics during unanticipated sidecutting. Objectives: This research sought to assess mechanical differences pre- and post-fatigue and with respect to limb dominance. Design: Repeated measures. Methods: Thirteen female collegiate soccer and field hockey players performed right and left unanticipated sidecutting following the Yo-Yo Intermittent Recovery test (Yo-Yo IR), a two minute treadmill run at a predicted VO2max, and maximum vertical jumps. Mechanical measures of ankle, knee, and hip motion were obtained during the stance phase of the cut. Repeated measures 2x2 ANOVAs were performed to look at fatigue and limb differences. Alpha level set a priori at 0.05. Results: At initial contact and peak stance, significant changes pre- to post-fatigue were observed. At initial contact there was a reduction in knee flexion angles along with increased ankle dorsiflexion angles postfatigue. At peak stance: increased knee adductor moments post-fatigue; greater ankle eversion moments on the dominant limb (DL) as well as increased eversion moments post-fatigue for both limbs. There was a differential effect of fatigue on peak hip abduction angles and hip internal rotation angles at initial contact which were altered in the DL only; decreased hip adductor moments occurred post-fatigue as well as decreased power absorption. Conclusions: Results from this study indicate that lower extremity mechanics are altered as an effect of fatigue such that injury risk may be elevated. / School of Physical Education, Sport, and Exercise Science

During heel-toe running, the vertical ground reaction force (VGRF) profile has both impact and active peaks. Although the mass-spring model (a single mass and a linear spring) is simple and useful to predict running characteristics, its simulation of VGRF profiles produces only a single peak rather than the double peak typically observed in running. In contrast, the mass-spring-damper model (two masses, two springs and a damper) produces a simulated force profile with two separate peak values. Running barefoot versus with shoes of varying stiffness produces VGRF profiles with quite different characteristics. The purpose of this study was to use the mass-spring and mass-spring-damper models to investigate the stiffness characteristics of human running in barefoot, hard-shoe and soft-shoe conditions. Ten recreational runners ran overground at 3.83 m/s and completed five trials of each footwear condition. Force data and two-dimensional kinematic data were recorded simultaneously at 1000 and 250 Hz respectively. Using the mass-spring model, vertical stiffnesses with the barefoot, hard-shoe and soft-shoe conditions were 27.6, 25.3 and 24.6 kN/m, respectively. Hard-shoe and soft-shoe material stiffnesses were about 150 and 100 kNm�����. Considering the leg and shoe as two springs in series, the leg's actual vertical stiffness could be estimated as 30 and 33 kNm����� for hard and soft-shoe conditions. The result suggested that runners increased their actual vertical stiffness with the sequence of barefoot, hard-shoe, and soft-shoe conditions. Using the mass-spring-damper model, the upper spring stiffness was relatively constant while the lower spring stiffness changed with footwear condition: 274, 136 and 126 kN/m, respectively. While it is mathematically convenient to model the leg and body with constant spring characteristics over time, physiologically it is likely that muscle-tendon stiffness does change during stance as muscle activity changes. This suggests that mass-spring models of running would be improved by time varying spring characteristics. Variable stiffness of the simple mass-spring model was tested using a smoothly varying stiffness function. This provided a significantly better force profile simulation for each of the footwear conditions than did the constant stiffness model. Further mass-spring-damper modeling may also be improved through incorporation of such time varying characteristics. / Graduation date: 2002

The purpose of the study was to investigate the effects of fatigue on the lower extremity landing strategies of males and females. Twelve recreationally active males (n = 6) and females (n = 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 20% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase of all jumps. At initial ground contact, males exhibited greater extension at the hip and knee and less plantar flexion than females. However, females performed more eccentric work during the impact phase of landing. Fatigue resulted in an increased extension at the hip, knee, and ankle for both genders, but did not have an effect on the peak VGRF. Fatigue also resulted in an increase in work performed at the ankle and an approximately equal reduction in work performed at the knee for both genders. Investigation of the peak powers revealed that as a result of fatigue, females utilized a landing strategy in which more energy was absorbed at the knee during the early part of the impact phase. The increased reliance on the knee musculature to dissipate kinetic energy during the impact phase of landing demonstrated by females may be a reason for the commonly seen gender disparities in injury rates. Furthermore, the shift towards energy absorption during the initial part of the impact phase when noncontact injuries are known to occur, exhibited by females, may indicate a greater injury risk for females. / School of Physical Education, Sport, and Exercise Science

Whole body vibration (WBV) is a training modality that involves an individual standing on a plate that provides vibrations at multiple frequencies and amplitudes. Improvements in muscular concentric force production such as power and strength have been extensively studied, however little work has been conducted looking at the effects of WBV on eccentric actions. The landing phase of a jump is an eccentric mechanism to decelerate the body as it prepares to stop or initiate another movement. This study sought to identify the effects of WBV on ground reaction forces, loading rates, valgus knee angles, frontal plane knee moment and jump height, as well as a higher order interaction between gender and time as a result of the vibration. An individualized frequency WBV protocol was utilized as 10 female and 9 male subjects completed drop jumps pre-vibration, post vibration and at 10 and 20 minutes post vibration. Baseline valgus knee angle increased 0.857 degrees post vibration, while remaining increased by 0.917 and 1.189 degrees at the 10 and 20 minute post vibration time intervals, respectively. Repeated measure ANOVA’s revealed that valgus knee angle significantly (p=0.011) increased post vibration. Gender comparisons revealed that females had a significantly greater knee moment (p=0.038) and males significantly jumped higher than females (p<0.001). As an end result following WBV, the subjects landed in significantly greater knee valgus, regardless of sex. Since it has been demonstrated that a knee in a valgus position increases the potential risk for anterior cruciate ligament injury, caution should be taken when combining WBV and jump training protocols. / School of Physical Education, Sport, and Exercise Science

This thesis investigates a simple dynamic model of the hind leg of a beetle during initiation of a step. The primary assumption was that the full load of the body was carried on the hind leg during this time. That is, the only forces on the body were that of the hind leg and gravity and their resultant produced forward acceleration. Only two dimensional models were used in this study. This was justified since the beetle is bilaterally symmetrical. However, it required the assumption that hind legs were positioned symmetrically and it limited the investigation to forward acceleration in a straight line. Models with two and three links were tested. The two link model assumed the body has no motion relative to the upper legs; that is the muscles were strong enough to prevent movement at the joint between body and leg. The three link model assumed only friction prevented movement at the joint between body and leg. Dynamic equations were developed using Lagrangian mechanics. These equations were integrated using the 4th order Runge-Kutta algorithm. Both models were driven by applying a constant torque at the joint between upper and lower segments. Driving torque was adjusted to minimize verical movement of body center of mass. Initial position of body center of mass relative to foot was varied to examine it's influence on both horizontal travel of body, center of mass and driving torque required for this travel. For both models horizontal travel was less dependent on initial height of body center-of-mass than on initial horizontal position. For both models required driving torque increased with decrease in initial height of body center-of-mass and with increase of initial horizontal distance from foot to body center-of-mass. For both models maximum horizontal travel was attained with minimum initial height of body center-of-mass and minimum initial horizontal distance between foot and body center-of-mass. For the two link model, maximum horizontal travel was approximately half of the total leg length while for the three link model the equivalent number was approximately one quarter, of total leg length. / Graduation date: 1992

The impact forces at landing are predominately absorbed by the hip, knee and ankle joints. Fatigue has been shown to increase the amount of work performed by the ankle and to reduce the work performed by the knee during landings. The purpose of this study was to assess the kinematic lower extremity motion and kinetic patterns during landings to fatigue, with and without ankle brace usage. Nine recreationally active males (n = 7) and females (n = 2) performed repetitive drop jumps to fatigue for an un-braced and braced condition. Kinematic and kinetic variables were assessed during the first 100 ms after ground impact. Due to the high skill level of the participants, none of the individuals reached a fatigued state. No significant main effect of fatigue was demonstrated on ankle work (p= 0.260). There was no significant main effect due to fatigue on the hip (p= 1.000), knee (p= 1.000) or ankle (p= 0.636) relative work contributions. Fatigue caused a shift toward a more erect landing position at initial ground contact (IGC). No significant main effect of the brace on hip (p= 0.437), knee (p= 0.283) or ankle (p= 0.314) angles was observed at IGC angles. The use of Ankle Stabilizing Orthosis® (ASO) ankle braces caused a shift toward greater knee contribution in a fatigued state. Plantar flexion angles were decreased the most during the braced un-fatigued condition. There was an inverse relationship between knee and hip angles as compared to ankle angles at IGC. When the hip and knee joint displayed less flexion at IGC, the ankle balanced the positions out by landing in more plantar flexion. / School of Physical Education, Sport, and Exercise Science

In gymnastics, females are often afflicted with lower extremity injuries during the landing phase of a backward rotating skill. The purpose of this study was to assess the efficacy of using a drop landing and backward somersault landing to compare and contrast the kinetic and kinematic differences between the two tasks in order to determine if a drop landing is a suitable representative task to analyze when examining landing injury mechanisms. Eleven female NCAA Division I gymnasts (age 19.3 ± 0.9 yrs; body height 1.66 ± 0.05 m; body mass 61.36 ± 6.02 kg) were recruited to perform drop landings and backward somersaults. Two force plates along with a 3D movement analysis system were used to collect kinetic and kinematic data. A repeated measures ANOVA was used to examine the differences in the variables with the significance level set at 0.05. There were mechanical differences and significance found between the peak vertical ground reaction forces, loading rate, kinetic and kinematic variables in the sagittal and frontal planes during the two tasks. It is evident that results may underestimate the effect of gymnastics landing impacts on risk of lower extremity injury because of the mechanical differences and significance found between the two tasks. / Access to thesis permanently restricted to Ball State community only.

Lau Tsz Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 57-66). / Text in English; abstracts in English and Chinese. / Lau Tsz Chung. / Acknowledgement --- p.i / Abstract --- p.ii / Table of contents --- p.v / List of Figures --- p.viii / List of Tables --- p.x / Introduction --- p.1 / Background --- p.1 / Statement of Problem --- p.3 / Research Question --- p.4 / Significance of the Study --- p.4 / Theoretical Contribution --- p.4 / Practical Contribution --- p.5 / Review of Literature --- p.7 / Load carrying on Level Ground --- p.7 / Research Method Involved --- p.8 / Modified Gait Pattern During Load Carriage --- p.9 / Trunk Posture --- p.10 / Low Back Pain --- p.11 / Posture and Back Pain --- p.12 / Load Carrying Studies in Children --- p.14 / Stair Walking --- p.15 / Compared with Level Walking --- p.15 / Temporal Characteristics --- p.17 / Kinematics Measurement --- p.18 / Stair Dimensions --- p.19 / Stair Walking with Load Carriage --- p.21 / Physiological Studies --- p.21 / Biomechanical Studies --- p.21 / Methodology --- p.24 / Design --- p.24 / Subject --- p.24 / Instrumentation --- p.25 / Motion Analysis System --- p.25 / School Bag --- p.25 / Experimental Set-up --- p.25 / Procedure --- p.26 / Term Definition --- p.27 / Data Analysis --- p.27 / Results --- p.29 / Ascending Stair --- p.29 / Posture --- p.29 / Effect on Load Weight --- p.29 / Effect on Load Carrying Method --- p.30 / Velocity --- p.30 / Parameters of Lower Extremities --- p.30 / Descending Stair --- p.31 / Posture --- p.31 / Effect on Load Weight --- p.31 / Effect on Load Carrying Method --- p.31 / Velocity --- p.32 / Parameters of Lower Extremities --- p.32 / Trend --- p.32 / Summary --- p.33 / Discussion --- p.35 / Ascending Stair --- p.35 / Posture --- p.35 / Different Load Weights --- p.35 / Different Carrying Methods --- p.39 / Velocity --- p.40 / Descending Stair --- p.42 / Posture --- p.42 / Velocity --- p.46 / Parameters of Lower Extremities --- p.47 / Trend --- p.48 / Back Pain --- p.49 / Recommended Carrying Load Method and Weight for Children --- p.50 / Limitations of the Study --- p.52 / Further Study --- p.53 / Conclusion --- p.56 / References --- p.57 / Appendix --- p.67 / Appendix A - The experimental Set-up --- p.67 / Appendix B - Subject Consent Form --- p.68 / Appendix C - Figures and Tables --- p.71