Biomedical subjects

Irene Davis

Publications and source records attributed to Irene Davis.

7 recordsLinked to original sources

PubMed2006

Effect of footwear on high and low arched runners' mechanics during a prolonged run.

INTRODUCTION: Running shoes are designed specifically for different foot types in order to reduce injuries. Running in the correct footwear matched for foot type may have a greater influence on mechanics when runners become exerted. Therefore, the purpose of this study was to evaluate changes in kinematics and kinetics over the course of a prolonged run when low (LA) and high (HA) arched runners wear motion control and cushioning shoes. METHODS: Twelve HA and 12 LA recreational runners were recruited for this study. Subjects ran in a motion control (MC) and cushion trainer (CT) shoe. Lower extremity kinematics and tibial accelerometry were collected while the runners ran at a self-selected training pace. The data were analyzed using a two-way (footwear x time) repeated measures ANOVA (p=0.05) for each arch type. RESULTS: Low arched runners: Peak tibial internal rotation decreased in the MC shoe and was increased in the CT over the course of the prolonged run. However, no interactions or main effects were noted for peak eversion or eversion excursion. High arched runners: No shoe by time interaction was observed for tibial shock. However, there was a main effect for shoe, with lower tibial shock associated with the CT shoe. CONCLUSION: In LA runners, MC shoes decreased tibial internal rotation compared to CT shoes over the course of a prolonged run. In HA runners, running in the CT shoes reduced tibial shock compared to the MC shoes.

Athletic Injuries↗

PubMed2006

The effect of a single treatment of the Protonics system on lower extremity kinematics during gait and the lateral step up exercise.

INTRODUCTION: Patellofemoral pain (PFP) is often attributed to abnormal patellar tracking. The Protonics knee orthosis was developed to reduce femoral internal rotation by altering pelvic alignment via hamstring activation. The purpose of this research was to determine if a single treatment with the orthosis improved lower extremity alignment during gait and the lateral step up exercise. We hypothesized that anterior pelvic tilt, hip internal rotation and adduction, and external rotation of the tibia with respect to the femur would decrease after use of the brace. METHODS: Nineteen females (23.4+/-3.1 year, 1.66+/-0.05 m, 65.3+/-20.4 kg) with chronic PFP participated. Three-dimensional kinematic data were collected for each subject at 60 Hz during pre-treatment (PRE), after a placebo condition with the orthosis set at zero resistance (PLAC), and post-treatment (POST). Treatment consisted of having the subject perform the rehabilitation exercises recommended by the Protonics manufacturer. A repeated measures ANOVA was performed on each dependent variable (alpha=0.05). RESULTS: This investigation did not verify the changes in alignment proposed by the manufacturer as a result of acute application of the Protonics system. However, after the use of the brace, pelvic rotation and hip hike were decreased during the lateral step up exercise. CONCLUSION: Based on the results of this study, it was concluded that a single application of the Protonics system did not alter anterior pelvic tilt, hip internal rotation and adduction, or tibial external rotation during the lateral step up and gait.

Adult↗

PubMed2006

The effect of gender, age, and lateral dominance on arch height and arch stiffness.

BACKGROUND: Arch structure is known to vary widely. However, it may be linked to intrinsic factors such as gender, age, and lateral dominance. Understanding the association between these factors and arch structure may be useful in understanding injury biases that exist between individuals with different foot types. METHODS: The foot structure of 145 subjects, 68 men and 77 women (18 to 65 years) was examined in this study. The arch height index, a measure of dorsal height normalized to foot length, and arch stiffness of both feet were measured in each subject. Comparisons of both arch height and arch stiffness were made between genders and between the dominant and nondominant feet. In addition, the relationship between both arch height and stiffness and age was examined. RESULTS: There was no difference between the arch height index of men and women; however, the arches in women were significantly less stiff (p = 0.00). There were no statistically significant relationships between increasing age and either arch height index or stiffness. The within-subject comparisons showed that the dominant foot had a significantly higher arch height index than the nondominant foot (p = 0.00). However, arch stiffness was not different between sides. There was a significant, but weak, relationship between arch height index and arch stiffness (p = 0.00, R2 = 0.09) with a higher arch height index corresponding to a stiffer arch. CONCLUSION: Understanding differences in arch structure may lend insight into the predilection for injury between genders, with increasing age, and between sides of a given subject.

Adolescent↗

PubMed2006

Core strength and lower extremity alignment during single leg squats.

INTRODUCTION/PURPOSE: Muscles of the trunk, hip, and knee influence the orientation of the lower extremity during weight bearing activities. The purpose of this study was threefold: first, to compare the orientation of the lower extremity during a single leg (SL) squat among male and female athletes; second, to compare the strength of muscle groups in the trunk, hips, and knees between these individuals; and third, to evaluate the association between trunk, hip, and knee strength and the orientation of the knee joint during this activity. METHODS: Twenty-four male and 22 female athletes participated in this study. Peak isometric torque was determined for the following muscle actions: trunk flexion, extension, and lateral flexion, hip abduction and external rotation, and knee flexion and extension. The frontal plane projection angle (FPPA) of the knee during a 45 degrees SL squat was determined using photo editing software. RESULTS: Males and females moved in opposite directions during the SL squat test (F(1,42) = 5.05, P = 0.03). Females typically moved toward more extreme FPPA during SL squats (P = 0.056), while males tended to move toward more neutral alignment (P = 0.066). Females also generated less torque in all muscle groups, with the exception of trunk extension. The projection angle of the knee during the SL squat test was most closely associated with hip external rotation strength. CONCLUSION: Using instruments suitable for a clinical setting, females were found to have greater FPPA and generally decreased trunk, hip, and knee isometric torque. Hip external rotation strength was most closely associated with the frontal plane projection angle.

Adolescent↗

PubMed2005

Kinetic asymmetry in female runners with and without retrospective tibial stress fractures.

Gait asymmetry may be linked to the tendency for runners to sustain chronic overuse injuries. This paper compares gait asymmetry in female runners who have never sustained a running-related injury to those who have sustained unilateral tibial stress fractures. The symmetry index was used to characterize asymmetry in the kinetics of both subject groups. There were three aims to this study: (1) to report natural levels of asymmetry for healthy, never-injured female runners, (2) to compare asymmetry levels between never-injured runners and those who have sustained stress fractures, and (3) to examine the kinetics between the involved and uninvolved limbs of runners who have sustained stress fractures. In all three aims, peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and peak instantaneous vertical loading rates, and peak shock were examined. In the never-injured runner group, natural levels of asymmetry ranged from 3.1% for peak vertical ground reaction force up to 49.8% for peak lateral ground reaction force. Symmetry indices were not significantly different in the runners who had previously sustained stress fractures. The involved limb of the previously injured runners demonstrated higher values for braking and vertical impact ground reaction force and peak shock. Interestingly, these runners appeared to have bilaterally-elevated lateral ground reaction forces and loading rates as compared to the never-injured group, although this was not statistically tested. This suggests that previously injured runners may be closer to the injury threshold and, thus, more susceptible. Asymmetry may simply influence the side on which they become injured.

Adolescent↗

PubMed2005

The relationship between forefoot, midfoot, and rearfoot static alignment in pain-free individuals.

STUDY DESIGN: Correlational study. OBJECTIVES: To determine whether, and to what degree, a relationship exists between forefoot angle and weight-bearing midfoot and rearfoot position. BACKGROUND: There have been conflicting reports with regard to the degree to which the structure of the foot may influence the function. The influence of forefoot structure on weight-bearing midfoot and rearfoot position has not been extensively investigated. METHODS AND MEASURES: Fifty-one healthy subjects participated in this study (26 male and 25 female). Forefoot angle was measured in prone as varus (positive numbers), neutral (0), or valgus (negative numbers). Navicular drop was measured from subtalar joint neutral to unilateral standing relaxed. Rearfoot angle was measured in relaxed single-limb stance as the angle between a line that bisected the calcaneus and a line that bisected the lower third of the leg. The relationships between forefoot angle and navicular drop, and between forefoot angle and relaxed rearfoot angle, were investigated. The same relationships were also investigated in the neutral forefoot subgroup when the sample was divided in 3 subgroups based on 1 standard deviation of forefoot angle. RESULTS: There is a significant relationship between forefoot angle and relaxed rearfoot angle (r = 0.52, P < .001), as well as between forefoot angle and navicular drop (r = 0.55, P < .001), in the whole sample (n = 51). Average degrees of forefoot angle in the neutral subgroup (between 1.0 degree and 8 degrees of varus) are not associated with predictable positions of relaxed rearfoot angle (r = 0.19, P = .24) or navicular drop (r = 0.01, P = .96). CONCLUSIONS: Based on the results of this study, there is a significant relationship between forefoot angle and relaxed rearfoot angle, as well as between forefoot angle and navicular drop, in healthy subjects. These relationships were not found when forefoot varus values were within a standard deviation of the sample mean.

Adult↗

PubMed2004

Differences in normal and perturbed walking kinematics between male and female athletes.

OBJECTIVE: To identify differences in lower extremity kinematic movement patterns between genders during walking through the application of an expected perturbation. DESIGN: Randomized limb kinematics were compared between healthy active males and females. BACKGROUND: Lower extremity kinematics during jump landing and cutting have been implicated as a potential source of the discrepancy in anterior cruciate ligament injury rates between genders. Kinematic differences between genders have been identified during tasks that are not provocative of anterior cruciate ligament injury but do result in increased ligament strain. Repetition of movement patterns that increase anterior cruciate ligament strain may increase the likelihood they will be reproduced during athletic tasks that produce force loads that exceed anterior cruciate ligament tensile strength. METHODS: Twenty subjects (10 women, 10 men) classified as a level I or II athlete underwent motion analyses while performing self-paced walking trials. Five trials were undisturbed, and five each with a platform translating either laterally or anteriorly at heel contact. Sagittal, frontal, and transverse hip angles as well as sagittal and frontal knee angles were collected during stance. RESULTS: Excursions in the frontal and transverse planes were greater at the hip and knee for females compared to males in each walking condition. The rate of these excursions also occurred more rapidly for females than males. There was no difference for joint angles at initial contact between genders, and there was no difference in the amount of sagittal plane excursion for the hip and knee when comparing genders. CONCLUSIONS: Females demonstrate characteristics during both normal and perturbed gait that may potentially contribute to increased anterior cruciate ligament strain. Repetition of these potentially harmful movement patterns during provocative athletic maneuvers may lead to anterior cruciate ligament injury. RELEVANCE: Females exhibit lower extremity kinematic patterns that differ from males. Female kinematic patterns may contribute to an increased risk for anterior cruciate ligament injury.

Adaptation, Physiological↗