STUDY DESIGN: Single-subject with repeated measures. OBJECTIVES: To determine if runners can use real-time visual feedback from an accelerometer to achieve immediate reductions in tibial acceleration and vertical-force loading rates. BACKGROUND: Stress fractures are a common injury among runners. Previous studies suggest that runners with higher than normal tibial acceleration and vertical-force loading rates are at increased risk for tibial stress fractures. If these runners can be trained to reduce the loading on their lower extremities, it may reduce their risk of stress fractures. METHODS: Five subjects participated in this study. All subjects ran on a treadmill, instrumented with force transducers, during a single 30-minute session that was divided into warm-up, feedback, no-feedback, and cool-down periods. During running, the subjects also wore an accelerometer taped to their distal right tibia. Peak positive acceleration of the tibia, vertical force impact peak, and average and instantaneous vertical-force loading rates were assessed at the end of the warm-up, feedback, and no-feedback periods. RESULTS: Single-subject analysis revealed that 4 of the 5 subjects had significant reductions in their peak positive acceleration at the end of the no-feedback period compared to the warm-up. In addition, all of the subjects had significant decreases in impact peak and vertical ground reaction force loading rates at the end of the no-feedback period. CONCLUSION: In a single session of training with real-time visual feedback, it appears that most runners can reduce the types of lower extremity loading associated with stress fractures. This may lead to training programs that reduce the risk of stress fractures for runners. LEVEL OF EVIDENCE: Prevention, level 5.

J Orthop Sports Phys Ther 2010;40(4):206-213, Epub 12 March 2010. doi:10.2519/jospt.2010.3166

KEY WORDS: accelerometer, gait retraining, ground reaction forces, stress fracture, tibia

STUDY DESIGN: Cross-sectional controlled laboratory study. OBJECTIVES: To investigate the kinematics of the hip, knee, and rearfoot in the frontal and transverse planes in female distance runners with a history of tibial stress fracture. BACKGROUND: Tibial stress fractures are a common overuse injury in runners, accounting for up to half of all stress fractures. Abnormal kinematics of the lower extremity may contribute to abnormal musculoskeletal load distributions, leading to an increased risk of stress fractures. METHODS: Thirty female runners with a history of tibial stress fracture were compared to 30 age-matched and weekly-running-distance–matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected using a motion capture system and a force platform, respectively, as subjects ran in the laboratory. Selected variables of interest were compared between the groups using a multivariate analysis of variance (MANOVA). RESULTS: Peak hip adduction and peak rearfoot eversion angles were greater in the stress fracture group compared to the control group. Peak knee adduction and knee internal rotation angles and all joint angles at impact peak were similar between the groups. CONCLUSION: Runners with a previous tibial stress fracture exhibited greater peak hip adduction and rearfoot eversion angles during the stance phase of running compared to healthy controls. A consequence of these mechanics may be altered load distribution within the lower extremity, predisposing individuals to stress fracture.

J Orthop Sports Phys Ther 2010;40(2):59-66. doi:10.2519/jospt.2010.3024

KEY WORDS: gait, injury, knee, lower leg, overuse, running

STUDY DESIGN: Cross-sectional experimental laboratory study. OBJECTIVE: To examine differences in running mechanics between runners who had previously sustained iliotibial band syndrome (ITBS) and runners with no knee-related running injuries. BACKGROUND: ITBS is the second leading cause of knee pain in runners and the most common cause of lateral knee pain. Despite its prevalence, few biomechanical studies have been conducted to better understand its aetiology. Because the iliotibial band has both femoral and tibial attachments, it is possible that atypical hip and foot mechanics could result in the development of ITBS. METHODS: The running mechanics of 35 females who had previously sustained ITBS were compared to 35 healthy age-matched and running distance-matched healthy females. Comparisons of hip, knee, and ankle 3-dimensional kinematics and internal moments during the stance phase of running gait were measured. RESULTS: The ITBS group exhibited significantly greater peak rearfoot invertor moment, peak knee internal rotation angle, and peak hip adduction angle compared to controls. No significant differences in peak rearfoot eversion angle, peak knee flexion angle, peak knee external rotator moment, or peak hip abductor moments were observed between groups. CONCLUSION: Females with a previous history of ITBS demonstrate a kinematic profile that is suggestive of increased stress on the iliotibial band. These results were generally similar to those reported for a prospective study conducted within the same laboratory environment.

J Orthop Sports Phys Ther 2010;40(2):52-58. Epub 31 December 2009. doi:10.2519/jospt.2010.3028

KEY WORDS: ankle, biomechanics, foot, running

J Orthop Sports Phys Ther 1984;6(2):116-122.

J Orthop Sports Phys Ther 1986;7(5):244-249.

The purpose of the study was to assess the effects of repeated in vivo loading on shock attenuation and mediolateral stability of running shoes using ground reaction force data. Six healthy subjects were each given a new pair of running shoes and asked to run 140 km between each of four experimental sessions. Ground reaction force data were collected for 10 successful trials/session using an A.M.T.I. force platform system. The mean values for selected ground reaction force parameters were evaluated using a single subject repeated measures design based on a 95% confidence interval. Mean parameter group data were also evaluated. The results support previous findings that material properties of the systems evaluated deteriorated resulting in a loss of shock absorbing capabilities (7.3%) but the magnitudes of the losses were far less than previously reported results (23-40%). The reason for this discrepancy is presumed to be the result of the different loading and evaluation methods used in the present study. The results also suggest that these changes are not totally deleterious since foot control seems to improve as cushioning is lost and foot control accounts for at least half of running shoe related injuries. A further implication of these results is that the initial "feel" or performance characteristics of a shoe may be misleading since reasonable functional changes appear to occur during the initial 300-400 km of wear.

J Orthop Sports Phys Ther 1988;10(2):47-53.

STUDY DESIGN: Cross-sectional experimental laboratory study. OBJECTIVES: To investigate the relationships between hip strength and hip kinematics, and between arch structure and knee kinematics during prolonged treadmill running in runners with and without patellofemoral pain syndrome (PFPS). BACKGROUND: Hip weakness can lead to excessive femoral motions that adversely affect patellofemoral joint mechanics. Similarly, foot mechanics, which are influenced by foot structure, are also known to influence patellofemoral joint mechanics. Thus, proximal and distal factors should be considered when studying individuals with PFPS. METHODS AND MEASURES: Twenty recreational runners with PFPS (5 male, 15 female) and 20 matched uninjured runners participated in the study. Hip abduction and hip external rotation isometric strength measurements were collected before and after a prolonged run, while the arch height index was recorded on all runners before the run. Lower extremity kinematic data were collected at the beginning and end of the run. Two-way repeated-measures analyses of variance (ANOVAs) were used for analysis. RESULTS: Both groups displayed decreases in hip abductor and external rotator strengths at the end of the run. The PFPS group displayed significantly lower hip abduction strength [(kg x cm)/body mass] compared to controls (PFPS group: begin 15.3, end 13.5; uninjured group: begin 17.3, end 15.4). At the end of the run, the level of association between hip abduction strength and the peak hip adduction angle for the PFPS group was statistically significant, indicating a strong relationship (r = -0.74). No other associations with hip strength were observed in either group. Arch height did not differ between groups and no significant association was observed between arch height and peak knee adduction angle during running. CONCLUSIONS: Runners with PFPS displayed weaker hip abductor muscles that were associated with an increase in hip adduction during running. This relationship became more pronounced at the end of the run. LEVEL OF EVIDENCE: Therapy, level 5.

J Orthop Sports Phys Ther. 2008;38(8):448-456, published online 15 April 2008. doi:10.2519/jospt.2008.2490

KEY WORDS: arch height index, hip abductor muscle strength, hip external rotator muscle strength, knee valgus

Study Design: Two-group posttest-only comparison. Objective: To assess the influence of the Q-angle on the 3-dimensional lower extremity kinematics during running. Background: An excessive Q-angle has been implicated in the development of knee injuries by altering the lower extremity locomotion kinematics. Previous investigations using 2-dimensional analyses during walking did not support this hypothesis. Methods and Measures: We hypothesized that individuals with Q-angles more than 15° would display an increase in rearfoot eversion and tibial internal rotation during running. Thirty-two nonimpaired subjects (men: n = 16, mean age = 22 ± 3 years; women: n = 16, mean age = 23 ± 3 years) ran over ground, and 3-dimensional kinematic data were collected from the right lower extremity. Subjects with a Q-angle of 15° or less comprised the low-Q-angle group, whereas those with Q-angles of more than 15° comprised the high-Q-angle group. Segment and joint maximum angles and the times when the maxima occurred during stance were measured. Results: The Q-angle magnitude did not increase the maximum segment or joint angles during running. The groups displayed similar maximum angles for rearfoot eversion (low Q-angle, -15.5 ± 5.0°; high Q-angle, -15.6 ± 6.6°) and tibial internal rotation (low Q-angle, -8.8 ± 4.8°; high Q-angle, -6.8 ± 5.1°). The high-Q-angle group (39.5 ± 16.3%) achieved maximum tibial internal rotation later in the stance phase than the low-Q-angle group (28.8 ± 10.7%). Conclusions: In support of the previous investigations involving Q-angle influences on kinematics, our study did not reveal any differences between groups in maximum joint or segment angles. The kinematic information did reveal that the high-Q-angle group displayed an increase in time to maximum tibial internal rotation. The impact of this single factor on producing knee injury is unknown.

J Orthop Sports Phys Ther. 2000;30(5):271-278.

Key Words: segment alignment, 3-dimensional kinematics, tibial rotation

In today's society, many women wear high-heeled shoes. However, the effect that shoes of different heel heights have on the biomechanics and energy cost of gait has not been fully investigated. In the present study, the energy cost and the lower extremity mechanics in shoes of different heel heights (1.25 cm, 3.81 cm, 5.08 cm, and 7.62 cm) were examined in 15 female subjects, seven of whom could be considered experienced high-heel wearers. Kinematic data from high-speed video and kinetic data from a force platform were collected to describe lower extremity mechanics while subjects walked overground at a speed of 4.2 km/hour. Heart rate and oxygen consumption were monitored while subjects walked on a treadmill, also at 4.2 km/hour. There were no significant differences in any of the parameters as a function of experience in wearing high heels; therefore, the data were pooled for further analysis. Analysis of the biomechanical data revealed that ankle plantar flexion, knee flexion, vertical ground reaction force, and the maximum anteroposterior braking force increased as a function of heel height. In addition, the timing of the subtalar and knee joint action was asynchronous with the increase in heel height. Metabolically, heart rate and oxygen consumption also increased with heel height. There were many significant differences between the 5.08-cm and the 7.62-cm heel conditions. Therefore, to maintain comfort and decrease the risk of injury, women may be advised not to wear shoes with a heel height greater than 5.08 cm.

J Orthop Sports Phys Ther. 1994;19(4):190-196.

Key Words: gait, high-heeled shoes, biomechanics, energy cost