The effect of ball-handling on lower extremity mechanics in soccer

HRS Honors Research Thesis ScholarshipNearly 240,000 soccer injuries are estimated to have occurred in the United States in 2014 with a high number of them non-contact in nature and involving the lower extremities. These injuries result in time-loss from training or match play, potential psychological consequences, and financial burdens. Epidemiological research suggests that these non-contact injuries may occur more frequently while ball-handling compared to defending in soccer. However, no prior studies have investigated the biomechanical implications of controlling a soccer ball with the feet while running and cutting that may help explain this finding. The purpose of this study was to compare knee and ankle joint moments and angles implicated in non-contact soccer injury mechanisms demonstrated during run-to-cut maneuvers performed with and without dribbling a soccer ball. Our hypothesis was that the cutting maneuvers performed while dribbling a ball would have a detrimental effect on biomechanical parameters associated with non-contact ankle and knee injuries. Seventeen healthy male collegiate soccer players participated in the study. Subjects performed ball-handling and running maneuvers while running straight ahead and also at a 45° cutting angle. All data were collected using three-dimensional motion capture with force plates embedded in the floor. Ball-handling had a significant effect on peak ankle internal rotation angle (p=0.010) and knee abduction angle (p=0.024). Changes in other parameters of interest, including peak ankle inversion moment and peak knee abduction moment, did not reach significance (p>0.05). In conclusion, ball-handling in soccer can detrimentally alter lower extremity joint mechanics of dynamic movements. The results of this study support the need for coaches to consider the implications of an athlete’s sport-specific movements when creating training programs for teams and individuals.A three-year embargo was granted for this item.Academic Major: Biomedical Scienc

Effects of Isolated Hip Abductor Fatigue on Frontal Plane Knee Mechanics

Purpose: Anterior cruciate ligament injuries and patellofemoral pain syndrome are both common and significant injuries to the knee that have been associated with hip weakness. Prospective studies have linked the risk of experiencing either injury to alterations in the frontal plane knee angle and moment during activity. These components of knee mechanics are theorized to be affected by hip abductor weakness. The purpose of this study was to identify the effects of isolated hip abductor fatigue-induced weakness on lower extremity kinematics and kinetics in recreationally active women

Hip External Rotator Strength Is Associated With Better Dynamic Control of the Lower Extremity During Landing Tasks

Hip external rotator strength is associated with better dynamic control of the lower extremity during landing tasks. J Strength Cond Res 30(1): 282–291, 2016—The purpose of this study was to determine the association between hip strength and lower extremity kinematics and kinetics during unanticipated single-leg landing and cutting tasks in collegiate female soccer players. Twenty-three National Collegiate Athletic Association division I female soccer players were recruited for strength testing and biomechanical analysis. Maximal isometric hip abduction and external rotation strength were measured using a hand-held dynamometer and expressed as muscle torque (force × femoral length) and normalized to body weight. Three-dimensional lower extremity kinematics and kinetics were assessed with motion analysis and force plates, and an inverse dynamics approach was used to calculate net internal joint moments that were normalized to body weight. Greater hip external rotator strength was significantly associated with greater peak hip external rotation moments (r = 0.47; p = 0.021), greater peak knee internal rotation moments (r = 0.41; p = 0.048), greater hip frontal plane excursion (r = 0.49; p = 0.017), and less knee transverse plane excursion (r = -0.56; p = 0.004) during unanticipated single-leg landing and cutting tasks. In addition, a statistical trend was detected between hip external rotator strength and peak hip frontal plane moments (r = 0.39; p = 0.06). The results suggest that females with greater hip external rotator strength demonstrate better dynamic control of the lower extremity during unanticipated single-leg landing and cutting tasks and provide further support for the link between hip strength and lower extremity landing mechanics

Influence of a knee brace intervention on perceived pain and patellofemoral loading in recreational athletes

Background: The current investigation aimed to investigate the effects of an intervention using knee bracing on pain symptoms and patellofemoral loading in male and female recreational athletes. Methods: Twenty participants (11 males & 9 females) with patellofemoral pain were provided with a knee brace which they wore for a period of 2 weeks. Lower extremity kinematics and patellofemoral loading were obtained during three sport specific tasks, jog, cut and single leg hop. In addition their self-reported knee pain scoreswere examined using the Knee injury and Osteoarthritis Outcome Score. Datawere collected before and after wearing the knee brace for 2 weeks. Findings: Significant reductions were found in the run and cut movements for peak patellofemoral force/pressure and in all movements for the peak knee abduction moment when wearing the brace. Significant improvements were also shown for Knee injury and Osteoarthritis Outcome Score subscale symptoms (pre: male= 70.27, female = 73.22 & post: male = 85.64, female = 82.44), pain (pre: male = 72.36, female = 78.89 & post: male = 85.73, female = 84.20), sport (pre: male = 60.18, female = 59.33 & post: male = 80.91, female =79.11), function and daily living (pre: male = 82.18, female = 86.00 & post: male = 88.91, female = 90.00) and quality of life (pre: male= 51.27, female= 54.89 & post: male= 69.36, female= 66.89). Interpretation:Male and female recreational athleteswho suffer frompatellofemoral pain can be advised to utilise knee bracing as a conservative method to reduce pain symptoms

Anticipatory Effects on Lower Extremity Neuromechanics During a Cutting Task

Context: Continued research into the mechanism of noncontact anterior cruciate ligament injury helps to improve clinical interventions and injury-prevention strategies. A better understanding of the effects of anticipation on landing neuromechanics may benefit training interventions. Objective: To determine the effects of anticipation on lower extremity neuromechanics during a single-legged land-and-cut task. Design: Controlled laboratory study. Setting: University biomechanics laboratory. Participants: Eighteen female National Collegiate Athletic Association Division I collegiate soccer players (age = 19.7 ± 0.8 years, height = 167.3 ± 6.0 cm, mass = 66.1 ± 2.1 kg). Intervention(s): Participants performed a single-legged land-and-cut task under anticipated and unanticipated conditions. Main Outcome Measure(s): Three-dimensional initial contact angles, peak joint angles, and peak internal joint moments and peak vertical ground reaction forces and sagittal-plane energy absorption of the 3 lower extremity joints; muscle activation of selected hip- and knee-joint muscles. Results: Unanticipated cuts resulted in less knee flexion at initial contact and greater ankle toe-in displacement. Unanticipated cuts were also characterized by greater internal hip-abductor and external-rotator moments and smaller internal knee-extensor and external-rotator moments. Muscle-activation profiles during unanticipated cuts were associated with greater activation of the gluteus maximus during the precontact and landing phases. Conclusions: Performing a cutting task under unanticipated conditions changed lower extremity neuromechanics compared with anticipated conditions. Most of the observed changes in lower extremity neuromechanics indicated the adoption of a hip-focused strategy during the unanticipated condition

The conjecturing process: perspectives in theory and implications in practice

[Abstract]: In this paper we analyze different types and stages of the conjecturing process. A classification of conjectures is discussed. A variety of problems that could lead to conjectures are considered from the didactical point of view. Results from a number of research studies are used to identify and investigate a number of questions related to the theoretical background of conjecturing as well as practical implications in the learning process

The conjecturing process: perspectives in theory and implications in practice

In this paper we analyze different types and stages of the conjecturing process. A classification of conjectures is discussed. A variety of problems that could lead to conjectures are considered from the didactical point of view. Results from a number of research studies are used to identify and investigate a number of questions related to the theoretical background of conjecturing as well as practical implications in the learning process