Influence of a custom foot orthotic intervention on lower extremity dynamics in healthy runners.

OBJECTIVE: To investigate the influence of a custom foot orthotic intervention on the lower extremity dynamics in healthy runners. DESIGN: Three-dimensional kinematics and kinetics were collected on 15 female runners (>15 miles per week) while each performed the over-ground running trials in either a shoe only or a shoe+custom foot orthotic condition. Kinematic and kinetic variables were analyzed using Paired Sample t-tests. BACKGROUND: Custom foot orthotics are frequently prescribed treatment modality for the management of overuse running injuries. Although it is generally accepted that a custom foot orthotic intervention produces positive clinical outcomes, it remains unclear what influence this therapeutic modality has on the dynamics of the lower extremity. METHODS: Each subject performed five acceptable over-ground running trials (3.6 m s(-1) +/-5%) with and without the custom foot orthotic intervention in a running shoe. Selected maximum ankle and knee joint angles and moments were measured during the stance phase. RESULTS: While wearing the custom foot orthotic, subjects exhibited significantly decreased maximum values in rearfoot eversion angle, rearfoot eversion velocity and internal ankle inversion moment. CONCLUSIONS: In this sample of healthy female runners, the custom foot orthotic intervention led to significant decreases in maximum values for ankle dynamics in the frontal plane and in the sagittal plane of the knee joint. Relevance It remains unclear how a custom foot orthotic intervention influences lower extremity dynamics to produce positive clinical outcomes. Furthering our understanding of the dynamic influence will not only inform improved prescription and manufacturing practices but may provide insight into the mechanisms that cause overuse injuries.

Effect of foot orthotics on rearfoot and tibia joint coupling patterns and variability.

The purpose of this study was to compare joint coupling patterns and variability of the rearfoot and tibia during running in subjects who were treated with two types of orthotic devices to that of controls. Eleven subjects with various lower extremity injuries were treated unsuccessfully with a standard orthotic, and then successfully with an inverted orthotic. Three-dimensional kinematic data were collected while subjects ran without orthoses and then in standard and inverted orthoses. Eleven healthy subjects ran without orthoses for comparison. The rearfoot inversion/eversion and tibial internal/external rotation joint coupling pattern and variability relationship was assessed using a vector coding technique. It was hypothesized that when the treated runners ran without orthotic devices, they would exhibit lower joint coupling angles and lower joint coupling variability compared to the controls. In addition, it was hypothesized that there would be no difference in the coupling angle or coupling variability between the standard and no orthotic conditions of the treated runners. Finally, it was hypothesized that coupling angle would decrease and variability would increase in the inverted versus the standard and non-orthotic conditions. No significant differences in joint coupling pattern or variability were observed between the treated and control subjects. In addition, no significant differences were noted between the orthotic conditions in the treated group. These results suggest that foot orthotic devices do not produce significant changes in rearfoot-tibial coupling. Therefore, the relief experienced with the inverted orthotic is likely due to factors other than alterations in this coupling.

Core stability and its relationship to lower extremity function and injury.

Core stability may provide several benefits to the musculoskeletal system, from maintaining low back health to preventing knee ligament injury. As a result, the acquisition and maintenance of core stability is of great interest to physical therapists, athletic trainers, and musculoskeletal researchers. Core stability is the ability of the lumbopelvic hip complex to prevent buckling and to return to equilibrium after perturbation. Although static elements (bone and soft tissue) contribute to some degree, core stability is predominantly maintained by the dynamic function of muscular elements. There is a clear relationship between trunk muscle activity and lower extremity movement. Current evidence suggests that decreased core stability may predispose to injury and that appropriate training may reduce injury. Core stability can be tested using isometric, isokinetic, and isoinertial methods. Appropriate intervention may result in decreased rates of back and lower extremity injury.

Core stability measures as risk factors for lower extremity injury in athletes.

INTRODUCTION/PURPOSE: Decreased lumbo-pelvic (or core) stability has been suggested to contribute to the etiology of lower extremity injuries, particularly in females. This prospective study compares core stability measures between genders and between athletes who reported an injury during their season versus those who did not. Finally, we looked for one or a combination of these strength measures that could be used to identify athletes at risk for lower extremity injury. METHODS: Before their season, 80 female (mean age = 19.1 +/- 1.37 yr, mean weight 65.1 +/- 10.0 kg) and 60 male (mean age = 19.0 +/- 0.90 yr, mean weight 78.8 +/- 13.3 kg) intercollegiate basketball and track athletes were studied. Hip abduction and external rotation strength, abdominal muscle function, and back extensor and quadratus lumborum endurance was tested for each athlete. RESULTS: Males produced greater hip abduction (males = 32.6 +/- 7.3%BW, females = 29.2 +/- 6.1%BW), hip external rotation (males = 21.6 +/- 4.3%BW, females = 18.4 +/- 4.1%BW), and quadratus lumborum measures (males = 84.3 +/- 32.5 s, females = 58.9 +/- 26.0 s). Athletes who did not sustain an injury were significantly stronger in hip abduction (males = 31.6 +/- 7.1%BW, females = 28.6 +/- 5.5%BW) and external rotation (males = 20.6 +/- 4.2%BW, females = 17.9 +/- 4.4%BW). Logistic regression analysis revealed that hip external rotation strength was the only useful predictor of injury status (OR = 0.86, 95% CI = 0.77, 0.097). CONCLUSION: Core stability has an important role in injury prevention. Future study may reveal that differences in postural stability partially explain the gender bias among female athletes.

High-arched runners exhibit increased leg stiffness compared to low-arched runners.

Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally, high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types. Differences in lower extremity kinetics in individuals with different foot types may have implications for new treatment strategies or preventative measures.

Orthotic intervention in forefoot and rearfoot strike running patterns.

OBJECTIVE: To compare the differential effect of custom orthoses on the lower extremity mechanics of a forefoot and rearfoot strike pattern. DESIGN: Fifteen subjects ran with both a forefoot and a rearfoot strike pattern with and without orthoses. Lower extremity kinematic and kinetic variables were compared between strike pattern and orthotic conditions. BACKGROUND: Foot orthoses have been shown to be effective in controlling excessive rearfoot motion in rearfoot strikers. The effect of orthotic intervention on rearfoot motion in forefoot strikers has not been previously reported. METHODS: Five trials were collected for each condition. Peak rearfoot eversion, eversion excursion, eversion velocity, peak inversion moment, and inversion work were compared between conditions. Kinematic variables in the sagittal plane of the rearfoot and in the frontal and sagittal plane of the knee were also determined. RESULTS: Increased rearfoot excursions and velocities and decreased peak eversion were noted in the forefoot strike pattern compared to the rearfoot strike pattern. Orthotic intervention, however,did not significantly change rearfoot motion in either strike pattern. Reductions in internal rotation and abduction of the knee were noted with orthotic intervention. CONCLUSIONS: Foot orthoses do not differentially effect rearfoot motion of a rearfoot strike and a forefoot strike running pattern. Orthotic intervention has a larger and more systematic effect on rearfoot kinetics compared to rearfoot kinematics.

Gender differences in lower extremity mechanics during running.

OBJECTIVE: To compare differences in hip and knee kinematics and kinetics in male and female recreational runners. DESIGN: Gait analysis of 20 men and 20 women recreational runners. BACKGROUND: Female runners are reported to be more likely to sustain certain lower extremity injuries compared to their male counterparts. This has been attributed, in part, to differences in their structure and it has been postulated that these structural differences may lead to differences in running mechanics. It was hypothesized that females would exhibit greater peak hip adduction, hip internal rotation, knee abduction and decreased knee internal rotation compared to their male counterparts. It was also hypothesized that females would exhibit greater hip and knee negative work in the frontal and transverse planes compared to males. METHODS: Comparisons of hip and knee three-dimentional joint angles and negative work during the stance phase of running gait were made between genders. RESULTS: Female recreational runners demonstrated a significantly greater peak hip adduction, hip internal rotation and knee abduction angle compared to men. Female recreational runners also demonstrated significantly greater hip frontal and transverse plane negative work compared to male recreational runners. CONCLUSION: Female recreational runners exhibit significantly different lower extremity mechanics in the frontal and transverse planes at the hip and knee during running compared to male recreational runners. RELEVANCE: Understanding the differences in running mechanics between male and female runners may lend insight into the etiology of different injury patterns seen between genders. In addition, these results suggest that care should be taken to account for gender when studying groups of male and female recreational runners.

Influence of gender on hip and knee mechanics during a randomly cued cutting maneuver.

OBJECTIVE: To investigate gender differences in three-dimensional hip and knee joint mechanics in collegiate athletes during a randomly cued cutting maneuver. DESIGN: Three-dimensional kinematics and kinetics were collected on 24 collegiate soccer players (12 females and 12 males) while each performed the cutting maneuver. In order to create a randomly cued condition, subjects were signaled by a lighted target board that directed them to perform one of three tasks. Hip and knee joint mechanics were compared between genders using one-tailed t-tests. BACKGROUND: Female athletes have an anterior cruciate ligament injury rate that is larger than their male counterparts. Gender differences in hip and knee joint mechanics during a randomly cued cutting maneuver have not been previously reported. METHODS: Five randomly cued cutting trials were included in the analysis. Selected peak hip and knee joint angles and moments were measured during the first 40 degrees of knee flexion across the stance phase. RESULTS: Females demonstrated significantly less peak hip abduction than did males. Otherwise, there were no gender differences in selected peak hip and knee joint kinematics and moments. CONCLUSIONS: Male and female collegiate soccer players demonstrate similar hip and knee joint mechanics while performing a randomly cued cutting maneuver. RELEVANCE: Because it is known that females incur a greater number of anterior cruciate ligament injuries than males, it is of interest to identify gender differences in lower extremity mechanics when performing sport specific tasks. Understanding of these differences will contribute to the development of prevention training programs.

Lower extremity stiffness: implications for performance and injury.

BACKGROUND: Lower extremity stiffness is thought to be an important factor in musculoskeletal performance. However, too little or too much stiffness is believed to increase the risk of musculoskeletal injury. PURPOSE: To provide a current update of the lower extremity stiffness literature as it pertains to both performance and injury. SUMMARY: It appears that increased stiffness is beneficial to performance. As well it appears that there may be an optimal amount of stiffness that allows for injury-free performance. There is some evidence that increased stiffness may be related to bony injuries and decreased stiffness may be associated with soft tissue injuries. Further investigations should evaluate the relationship between stiffness and injury prospectively. Initial reports suggest that stiffness can be modified in response to the external environment or verbal cues. RELEVANCE: A greater understanding of the role of stiffness in both performance and injury will provide a stronger foundation for the development of optimal training intervention programs.

Hip strength in females with and without patellofemoral pain.

STUDY DESIGN: Cross-sectional. OBJECTIVES: To determine if females with anterior knee pain are more likely to demonstrate hip abduction or external rotation weakness than a similar, asymptomatic, age-matched control group. BACKGROUND: Diminished hip strength has been implicated as being contributory to lower-extremity malalignment and patellofemoral pain. The identification of reliable and consistent patterns of weakness in this population may assist health care professionals establish a more effective treatment plan. METHODS AND MEASURES: Hip abduction and external rotation isometric strength measurements were recorded for the injured side of 15 female subjects with patellofemoral joint pain (mean +/- SD age, 15.7 +/- 2.7 years; age range, 12-21 years). These were compared with strength measurements from the corresponding hip of 15 age-matched female control subjects (mean +/- SD age, 15.7 +/- 2.7 years; age range, 12-21 years). All strength measurements were made using hand-held dynamometers. RESULTS: Subjects with patellofemoral pain demonstrated 26% less hip abduction strength (P<.001) and 36% less hip external rotation strength (P<.001) than similar age-matched controls. CONCLUSIONS: The results indicate that young women with patellofemoral pain are more likely to demonstrate weakness in hip abduction as well as external rotation than age-matched women who are not symptomatic.

Dual-function foot orthosis: effect on shock and control of rearfoot motion.

Orthoses have been designed that claim to both reduce shock and control rearfoot motion. It was hypothesized that the dual-purpose soft orthosis would reduce shock and control rearfoot motion greater than a no-orthotic condition. Three-dimensional kinematic and kinetic data were collected along with tibial acceleration while subjects ran in no-orthotic, the dual-purpose orthotic, and a rigid orthotic condition. Variables of interest were eversion excursion, peak eversion, eversion velocity, peak positive acceleration, loading rate, and leg stiffness. None of the evaluated variables were significantly different (p = .05) between the three conditions. These data suggest that shock attenuation and rearfoot motion cannot be controlled by the orthoses used in this study for a group of healthy runners.