Severity of Overuse Injury Impacts Self-Efficacy and Quality of Life in Runners: A 2-Year Prospective Cohort Study.

CONTEXT: While 55 million Americans incorporate running into their exercise routines, up to 65% of runners sustain an overuse injury annually. It has been consistently shown that regular physical activity positively impacts quality of life (QOL), an essential public health indicator; however, the impact of running-related injuries on QOL is unknown. This study seeks to determine whether overuse injury severity impacts QOL in recreational runners, and if self-efficacy mediates this relationship. DESIGN: Community-based prospective cohort study of 300 runners who had been running injury free for at least 5 miles/wk in the past 6 months. METHODS: Self-efficacy for running and QOL measures (Short Form-12 Physical Component and Mental Component, Satisfaction with Life, Positive Affect and Negative Affect) were assessed at baseline, time of injury, and follow-up visits. Over 2 years of observation, overuse injuries were diagnosed by an orthopedic surgeon and injured runners were referred to a physical therapist. RESULTS: Injury severity was significantly (P < .01) related with 2 indices of QOL, such that the effect of injury severity was -2.28 units on the Short Form-12 physical component and -0.73 units on positive affect. Self-efficacy accounted for 19% and 48% of the indirect effects on Short Form-12 physical component and positive affect, respectively. CONCLUSIONS: Since self-efficacy is a modifiable factor related to decreased QOL, these findings have important clinical implications for rehabilitation interventions.

Spatiotemporal and Kinematic Comparisons Between Anthropometrically Paired Male and Female Soldiers While Walking With Heavy Loads.

INTRODUCTION: Limited work comparing the effect of heavier carried loads (greater than 30 kg) between men and women has attributed observed differences to sex with the possibility that anthropometric differences may have contributed to those discrepancies. With the recent decision permitting women to enter Combat Arms roles, knowledge of sex-based differences in gait response to load carriage is more operationally relevant, as military loads are absolute and not relative to body weight. The purpose of this study was to describe differences in gait parameters at light to heavy loads between anthropometrically similar male and female soldiers. MATERIALS AND METHODS: Eight female and 8 male soldiers, frequency-matched (1-to-1) on height (±0.54 cm) and mass (±0.52 kg), walked at 1.34 m∙s-1 for 10-min bouts on a level treadmill while unloaded (BM) and then carrying randomized vest-borne loads of 15, 35, and 55 kg. Spatiotemporal and kinematic data were collected for 30 s after 5 min. Two-way repeated measures analyses of variance were conducted to compare the gait parameter variables between sexes at each load. RESULTS: As load increased, overall, the percent double support increased, step frequency increased, stride length decreased, hip and ankle range of motion (ROM) increased, and vertical center of mass (COM) displacement increased. Sex-based significant differences were observed in knee ROM and mediolateral COM displacement. Among the male participants, knee ROM increased significantly for all loads greater than BM. For mediolateral COM displacement, male remained constant as load increased, whereas female values decreased between BM and 35 kg. CONCLUSIONS: Spatiotemporal and kinematic differences in gait parameters were primarily because of increases in load magnitude. The observed sex-related differences with increasing loads suggest that women may require a more stable gait to support the additional load carried.

A 2-Year Prospective Cohort Study of Overuse Running Injuries: The Runners and Injury Longitudinal Study (TRAILS).

BACKGROUND: The National Center for Injury Prevention and Control, noting flaws in previous running injury research, called for more rigorous prospective designs and comprehensive analyses to define the origin of running injuries. PURPOSE: To determine the risk factors that differentiate recreational runners who remain uninjured from those diagnosed with an overuse running injury during a 2-year observational period. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Inclusion criteria were running a minimum of 5 miles per week and being injury free for at least the past 6 months. Data were collected at baseline on training, medical and injury histories, demographics, anthropometrics, strength, gait biomechanics, and psychosocial variables. Injuries occurring over the 2-year observation period were diagnosed by an orthopaedic surgeon on the basis of predetermined definitions. RESULTS: Of the 300 runners who entered the study, 199 (66%) sustained at least 1 injury, including 73% of women and 62% of men. Of the injured runners, 111 (56%) sustained injuries more than once. In bivariate analyses, significant ( P ≤ .05) factors at baseline that predicted injury were as follows: Short Form Health Survey-12 mental component score (lower mental health-related quality of life), Positive and Negative Affect Scale negative affect score (more negative emotions), sex (higher percentage of women were injured), and knee stiffness (greater stiffness was associated with injury); subsequently, knee stiffness was the lone significant predictor of injury (odds ratio = 1.18) in a multivariable analysis. Flexibility, quadriceps angle, arch height, rearfoot motion, strength, footwear, and previous injury were not significant risk factors for injury. CONCLUSION: The results of this study indicate the following: (1) among recreational runners, women sustain injuries at a higher rate than men; (2) greater knee stiffness, more common in runners with higher body weights (≥80 kg), significantly increases the odds of sustaining an overuse running injury; and (3) contrary to several long-held beliefs, flexibility, arch height, quadriceps angle, rearfoot motion, lower extremity strength, weekly mileage, footwear, and previous injury are not significant etiologic factors across all overuse running injuries.

An integrative modeling approach for the efficient estimation of cross sectional tibial stresses during locomotion.

The purpose of this research was to utilize a series of models to estimate the stress in a cross section of the tibia, located 62% from the proximal end, during walking. Twenty-eight male, active duty soldiers walked on an instrumented treadmill while external force data and kinematics were recorded. A rigid body model was used to estimate joint moments and reaction forces. A musculoskeletal model was used to gather muscle length, muscle velocity, moment arm and orientation information. Optimization procedures were used to estimate muscle forces and finally internal bone forces and moments were applied to an inhomogeneous, subject specific bone model obtained from CT scans to estimate stress in the bone cross section. Validity was assessed by comparison to stresses calculated from strain gage data in the literature and sensitivity was investigated using two simplified versions of the bone model-a homogeneous model and an ellipse approximation. Peak compressive stress occurred on the posterior aspect of the cross section (-47.5 ± 14.9 MPa). Peak tensile stress occurred on the anterior aspect (27.0 ± 11.7 MPa) while the location of peak shear was variable between subjects (7.2 ± 2.4 MPa). Peak compressive, tensile and shear stresses were within 0.52 MPa, 0.36 MPa and 3.02 MPa respectively of those calculated from the converted strain gage data. Peak values from a inhomogeneous model of the bone correlated well with homogeneous model (normal: 0.99; shear: 0.94) as did the normal ellipse model (r=0.89-0.96). However, the relationship between shear stress in the inhomogeneous model and ellipse model was less accurate (r=0.64). The procedures detailed in this paper provide a non-invasive and relatively quick method of estimating cross sectional stress that holds promise for assessing injury and osteogenic stimulus in bone during normal physical activity.

Spatiotemporal Parameters are not Substantially Influenced by Load Carriage or Inclination During Treadmill and Overground Walking.

Influences of load carriage and inclination on spatiotemporal parameters were examined during treadmill and overground walking. Ten soldiers walked on a treadmill and overground with three load conditions (00 kg, 20 kg, 40 kg) during level, uphill (6% grade) and downhill (-6% grade) inclinations at self-selected speed, which was constant across conditions. Mean values and standard deviations for double support percentage, stride length and a step rate were compared across conditions. Double support percentage increased with load and inclination change from uphill to level walking, with a 0.4% stance greater increase at the 20 kg condition compared to 00 kg. As inclination changed from uphill to downhill, the step rate increased more overground (4.3 ± 3.5 steps/min) than during treadmill walking (1.7 ± 2.3 steps/min). For the 40 kg condition, the standard deviations were larger than the 00 kg condition for both the step rate and double support percentage. There was no change between modes for step rate standard deviation. For overground compared to treadmill walking, standard deviation for stride length and double support percentage increased and decreased, respectively. Changes in the load of up to 40 kg, inclination of 6% grade away from the level (i.e., uphill or downhill) and mode (treadmill and overground) produced small, yet statistically significant changes in spatiotemporal parameters. Variability, as assessed by standard deviation, was not systematically lower during treadmill walking compared to overground walking. Due to the small magnitude of changes, treadmill walking appears to replicate the spatiotemporal parameters of overground walking.

The Relationships between Age and Running Biomechanics.

UNLABELLED: Running has high injury rates, especially among older runners. Most aging literature compares young with old runners without accounting for the progression of biomechanics throughout the lifespan. We used age as a continuous variable to investigate the continuum of age-related gait adaptations in running along with determining the chronology and rate of these adaptations. PURPOSE: This study aimed to identify the relations among age and selected running biomechanics throughout the range of 18-60 yr. METHODS: Experienced (n = 110) healthy runners (male, 54%) provided informed consent and ran at their training pace while motion and force data were captured. Kinematics, ground reaction forces (GRF), and lower limb joint torques and powers were correlated with age using Pearson product-moment correlations and linear regression. RESULTS: Running velocity was inversely related to age (r = -0.27, P = 0.005) because of decreased stride length (r = -0.25, P = 0.008) but not rate. Peak vertical GRF (r = -0.23, P = 0.016) and peak horizontal propulsive GRF decreased with age (r = -0.38, P < 0.0001). Peak ankle torque (r = -0.32, P = 0.0007) and peak negative (r = 0.34, P = 0.0003) and positive (r = -0.37, P < 0.0001) ankle power decreased with age. Age-based regression equations and per-year reductions in all variables significantly related to age are reported. CONCLUSIONS: Data support previous work showing lower GRF, stride length, and velocity in old runners. Results are novel in showing the rate of decline in running biomechanics on a per-year basis and that mechanical reductions at the ankle but not at the hip or knee were correlated with age, confirming a previous observation of biomechanical plasticity with age showing reduced ankle but not hip function in gait.

Characterization of Foot-Strike Patterns: Lack of an Association With Injuries or Performance in Soldiers.

OBJECTIVES: Characterize the distribution of foot-strike (FS) patterns in U.S. Army Soldiers and determine if FS patterns are related to self-reported running injuries and performance. METHODS: 341 male Soldiers from a U.S. Army Combined Arms Battalion ran at their training pace for 100 meters, and FSs were recorded in the sagittal plane. Participants also completed a survey related to training habits, injury history, and run times. Two researchers classified FS patterns as heel strike (HS) or nonheel strike (NHS, combination of midfoot strike and forefoot strike patterns). Two clinicians classified the musculoskeletal injuries as acute or overuse. The relationship of FS type with two-mile run time and running-related injury was analyzed (p ≤ 0.05). RESULTS: The Soldiers predominately landed with an HS (87%) and only 13% were characterized as NHS. Running-related injury was similar between HS (50.3%) and NHS (55.6%) patterns (p = 0.51). There was no difference (p = 0.14) between overuse injury rates between an HS pattern (31.8%) and an NHS pattern (31.0%). Two-mile run times were also similar, with both groups averaging 14:48 minutes. CONCLUSION: Soldiers were mostly heel strikers (87%) in this U.S. Army Combined Arms Battalion. Neither FS pattern was advantageous for increased performance or decreased incidence of running-related injury.

Lower extremity biomechanical changes associated with symmetrical torso loading during simulated marching.

The dose-response relationship between biomechanical variables and the magnitude of external loads is unclear. The use of different load distributions (e.g., pack types) may confound results because of changes in torso center of mass. Therefore, we examined the relationship between load magnitude and sagittal plane lower extremity mechanics of Soldiers walking with two symmetrically distributed loads. Fourteen Soldiers marched on a force-sensing treadmill at 1.34 m/s for 10 minutes with no load (BW_00) and while wearing vest-borne loads of 15 kg (BW_15) and 55 kg (BW_55). The effects of the loads on sagittal plane joint angles and moments were compared using 1-way repeated measures analyses of variance. Compared with BW_00, knee extension moment increased with the 15- and the 55-kg loads (both p < 0.003), confirming previously reported load-related biomechanical responses. Knee moment increases during early stance appeared to be the primary means by which the lower extremity counteracted BW_15 during early stance; in contrast, hip extensors and ankle dorsiflexors appeared to be the primary muscular efforts responsible for propulsion during late stance. Findings elucidated the effects of load magnitude on lower extremity mechanics without postural changes that result from pack-related shifts in torso center of mass.

Comparison of methods for kinematic identification of footstrike and toe-off during overground and treadmill running.

When analysing gait, the identification of the period of stance is often needed. Forceplates are typically used, but in their absence kinematic data can be employed. Five kinematic methods have been previously described in the literature. However, these methods have not been compared to each other for overground or treadmill running. Therefore, the purpose of this study was to compare these five kinematic methods of identifying the stance phase with vertical ground reaction force data both during overground and treadmill running. We recruited forty recreational runners (20 males) for this study. Twenty runners underwent an instrumented gait analysis during overground running, and twenty were tested during instrumented treadmill running. All runners ran at 3.35 m/s. Each kinematic method was compared with stance identified from the vertical ground reaction force (gold standard) for overground running. This method was then repeated for treadmill running. Two methods were found to be valid and reliable for determining footstrike. These were the time when the distal heel marker reached a minimum vertical position, and when the vertical velocity of this same marker changed from negative to positive. These methods had absolute errors that ranged from 22.4 ms to 24.6 ms for both modes of running. Toe-off was best identified using peak knee extension, with absolute errors of 4.9 ms for overground running and 5.2 ms for treadmill running. Utilising automated kinematic methods of determining stance will aid researchers studying running when forceplates are unavailable.

Comparison of lower extremity kinematic curves during overground and treadmill running.

Researchers conduct gait analyses utilizing both overground and treadmill modes of running. Previous studies comparing these modes analyzed discrete variables. Recently, techniques involving quantitative pattern analysis have assessed kinematic curve similarity in gait. Therefore, the purpose of this study was to compare hip, knee and rearfoot 3-D kinematics between overground and treadmill running using quantitative kinematic curve analysis. Twenty runners ran at 3.35 m/s ± 5% during treadmill and overground conditions while right lower extremity kinematics were recorded. Kinematics of the hip, knee and rearfoot at footstrike and peak were compared using intraclass correlation coefficients. Kinematic curves during stance phase were compared using the trend symmetry method within each subject. The overall average trend symmetry was high, 0.94 (1.0 is perfect symmetry) between running modes. The transverse plane and knee frontal plane exhibited lower similarity (0.86-0.90). Other than a 4.5 degree reduction in rearfoot dorsiflexion at footstrike during treadmill running, all differences were ≤1.5 degrees. 17/18 discrete variables exhibited modest correlations (>0.6) and 8/18 exhibited strong correlations (>0.8). In conclusion, overground and treadmill running kinematic curves were generally similar when averaged across subjects. Although some subjects exhibited differences in transverse plane curves, overall, treadmill running was representative of overground running for most subjects.

Impact of fatigue on gender-based high-risk landing strategies.

PURPOSE: Noncontact anterior cruciate ligament (ACL) injuries carry significant short- and long-term morbidity, particularly in females. To combat this epidemic, neuromuscular training has evolved aimed at modifying high-risk lower-limb biomechanics. However, injury rates and the gender disparity in these rates remain, suggesting that key components of the injury mechanism continue to be ignored. This study examined the potential contributions of neuromuscular fatigue to noncontact ACL injuries. METHODS: Ten male and 10 female NCAA athletes had 3D lower-limb-joint kinematics and kinetics recorded during 10 drop jumps, both before and after fatigue. Mean subject-based initial-contact (N = 9) and peak stance-phase kinematic (N = 9) and normalized (mass x height) kinetic (N = 9) parameters were quantified before and after fatigue and submitted to a three-way ANOVA to determine for the main effects of leg, gender, and fatigue. A Bonferroni corrected alpha level of 0.002 was adopted for all statistical comparisons. RESULTS: Females landed with more initial ankle plantar flexion and peak-stance ankle supination, knee abduction, and knee internal rotation compared with men. They also had larger knee adduction, abduction, and internal rotation, and smaller ankle dorsiflexion moments. Fatigue increased initial and peak knee abduction and internal rotation motions and peak knee internal rotation, adduction, and abduction moments, with the latter being more pronounced in females. CONCLUSIONS: Fatigue-induced modifications in lower-limb control may increase the risk of noncontact ACL injury during landings. Gender dimorphic abduction loading in the presence of fatigue also may explain the increased injury risk in women. Understanding fatigue effects at both the central and peripheral levels will further afford elucidation of the ACL injury mechanism and, hence, more successful prevention strategies.