It is unknown if female runners who have sustained multiple iliotibial band syndrome occurrences run differently compared with runners who developed the injury once or controls. Therefore, the purpose of this study was to determine if differences existed in coordination patterns and coordination variability among female runners with recurrent iliotibial band syndrome, 1 iliotibial band syndrome occurrence, and controls. Overground running trials were collected for 36 female runners (n = 18 controls). Lower extremity coordination patterns were examined during running via a vector coding analysis. Coordination variability was calculated via the ellipse area method. Separate 1-way (group) Kruskal–Wallis tests were performed to compare each coordination pattern and coordination variability. Lower extremity coordination between frontal plane hip–transverse plane hip, frontal plane pelvis–frontal plane thigh, and frontal plane thigh–transverse plane shank was similar among groups and so may not be related to the risk of iliotibial band syndrome. Runners with 1 iliotibial band syndrome occurrence demonstrated greater coordination variability for 2 of 3 couplings compared with both controls and runners with recurrent iliotibial band syndrome. Thus, the number of previous injury episodes may influence coordination variability in female runners with a history of iliotibial band syndrome.
Eric Foch and Clare E. Milner
Eric Foch and Clare E. Milner
Proximal factors such as excessive frontal plane pelvis and trunk motion have been postulated to be biomechanical risk factors associated with iliotibial band syndrome. In addition, lateral core endurance deficiencies may be related to increased pelvis and trunk motion during running. The purpose of this cross-sectional investigation was to determine if differences in biomechanics during running, as well as lateral core endurance exist between female runners with previous iliotibial band syndrome and controls. Gait and lateral core endurance were assessed in 34 female runners (17 with previous iliotibial band syndrome). Multivariate analysis of variance was performed to assess between group difference in pelvis, trunk, hip, and knee variables of interest. Runners with previous iliotibial band syndrome exhibited similar peak trunk lateral flexion, peak contralateral pelvic drop, peak hip adduction, and peak external knee adduction moment compared with controls. In addition, trunk-pelvis coordination was similar between groups. Contrary to our hypotheses, both groups exhibited trunk ipsilateral flexion. Lateral core endurance was not different between groups. These findings provide the first frontal plane pelvis and trunk kinematic data set in female runners with previous iliotibial band syndrome. Frontal plane pelvis and trunk motion may not be associated with iliotibial band syndrome.
Richard A. Brindle, David Ebaugh and Clare E. Milner
Context: Side-lying hip abductor strength tests are commonly used to evaluate muscle strength. In a “break” test, the tester applies sufficient force to lower the limb to the table while the patient resists. The peak force is postulated to occur while the leg is lowering, thus representing the participant’s eccentric muscle strength. However, it is unclear whether peak force occurs before or after the leg begins to lower. Objectives: To determine intrarater reliability and construct validity of a hip abductor eccentric strength test. Design: Intrarater reliability and construct validity study. Participants: Twenty healthy adults (26  y; 1.66 [0.06] m; 62.2 [8.0] kg) made 2 visits to the laboratory at least 1 week apart. Main Outcome Measures : During the hip abductor eccentric strength test, a handheld dynamometer recorded peak force and time to peak force, and limb position was recorded via a motion capture system. Intrarater reliability was determined using intraclass correlation, SEM, and minimal detectable difference. Construct validity was assessed by determining if peak force occurred after the start of the lowering phase using a 1-sample t test. Results: The hip abductor eccentric strength test had substantial intrarater reliability (intraclass correlation(3,3) = .88; 95% confidence interval, .65–.95), SEM of 0.9 %BWh, and a minimal detectable difference of 2.5 %BWh. Construct validity was established as peak force occurred 2.1 (0.6) seconds (range: 0.7–3.7 s) after the start of the lowering phase of the test (P ≤ .001). Conclusion: The hip abductor eccentric strength test is a valid and reliable measure of eccentric muscle strength. This test may be used clinically to assess changes in eccentric muscle strength over time.
Douglas W. Powell, Benjamin Long, Clare E. Milner and Songning Zhang
The medial longitudinal arch plays a major role in determining lower extremity kinematics. Thus, it is necessary to understand the dynamics of the arch structure in response to load. The purpose of this study was to examine arch function in high- and low-arched feet during a vertical loading condition. Ten high- and ten low-arched females performed five trials in a sit-to-stand exercise. Ground reaction force (1200 Hz) and three-dimensional kinematics (240 Hz) were collected simultaneously. The high-and low-arched athletes had no differences in vertical deformation of the arch. High-arched participants were less everted than the low-arched athletes; furthermore, the high-arched athletes had smaller mid-forefoot eversion excursions. Differences between the high-arched and low-arched athletes occur through and motion at the mid-forefoot joint.
Jacob K. Gardner, Songning Zhang, Max R. Paquette, Clare E. Milner and Elizabeth Brock
The recent popularity of unstable shoes has sparked much interest in the efficacy of the shoe design. Anecdotal evidence suggests that earlier designs appear bulky and less aesthetically appealing for everyday use. The purpose of this study was to examine effects of a second generation unstable shoe on center of pressure (COP), ground reaction force (GRF), kinematics, and kinetics of the ankle joint during level walking at normal and fast speeds. In addition, findings were compared with results from the first generation shoe. Fourteen healthy males performed five successful level walking trials in four testing conditions: walking in unstable and control shoes at normal (1.3 m/s) and fast (1.8 m/s) speeds. The unstable shoe resulted in an increase in mediolateral COP displacement, first peak vertical GRF loading rate, braking GRF, ankle eversion range of motion (ROM), and inversion moment; as well as a decrease in anteroposterior COP displacement, second peak vertical GRF, ankle plantarflexion ROM, and dorsiflexion moment. Only minor differences were found between the shoe generations. Results of the generational comparisons suggest that the lower-profile second generation shoe may be as effective at achieving the desired unstable effects while promoting a smoother transition from heel contact through toe off compared with the first generation shoe.
David R. Mullineaux, Clare E. Milner, Irene S. Davis and Joseph Hamill
The appropriateness of normalizing data, as one method to reduce the effects of a covariate on a dependent variable, should be evaluated. Using ratio, 0.67-nonlinear, and fitted normalizations, the aim of this study was to investigate the relationship between ground reaction force variables and body mass (BM). Ground reaction forces were recorded for 40 female subjects running at 3.7 ± 0.18 m·s–1 (mass = 58 ± 6 kg). The explained variance for mass to forces (peak-impact-vertical = 70%; propulsive-vertical = 27%; braking = 40%) was reduced to < 0.1% for mass to ratio normalized forces (i.e., forces/BM1) with statistically significantly different power exponents (p < 0.05). The smaller covariate effect of mass on loading rate variables of 2–16% was better removed through fitted normalization (e.g., vertical-instantaneous-loading-rate/BM0.69±0.93; ±95% CI) with nonlinear power exponents ranging from 0.51 to 1.13. Generally, these were similar to 0.67 as predicted through dimensionality theory, but, owing to the large confidence intervals, these power exponents were not statistically significantly different from absolute or ratio normalized data (p > 0.05). Further work is warranted to identify the appropriate method to normalize loading rates either to mass or to another covariate. Ratio normalization of forces to mass, as predicted through Newtonian mechanics, is recommended for comparing subjects of different masses.