Alterations in Achilles tendon stress and strain across a range of running velocities.

Running has a high incidence of overuse injuries. Achilles tendon (AT) injuries may occur due to high forces and repetitive loading during running. Foot strike pattern and cadence have been linked to the magnitude of AT loading. The effect of running speed on AT stress and strain, muscle forces, gait parameters and running kinematics is not well addressed in recreational runners with lower pace of running. Twenty-two female participants ran on an instrumented treadmill between 2.0 and 5.0 m/s. Kinetic and kinematic data were obtained. AT cross-sectional area data were collected using ultrasound imaging. Inverse dynamics with static optimization was used to calculate muscle forces and AT loading. AT stress, strain and cadence increased with greater running speed. Foot inclination angle indicated a rearfoot strike pattern among all participants, which increased as running speed increased but the latter plateaued after 4.0 m/s. The soleus contributed more force in running compared to the gastrocnemius throughout all speeds. Highest running speeds had the most stress on the AT, with changes to foot inclination angle and cadence. Understanding the relation of AT loading variables with running speed may aid in understanding how applied load may influence injury.

Muscle force characteristics of male and female collegiate cross-country runners during overground running.

Males and females demonstrate unique running mechanics that may contribute to sex-related differences in common running related injuries. Understanding differences in muscle forces during running may inform intervention approaches, such as gait retraining addressing muscle force distribution. The purpose of this study was to compare muscle force characteristics and inter-trial variability between males and females during running. Twenty female and 14 male collegiate cross-country runners were examined. Three-dimensional kinetic and kinematic data were collected during overground running and used to estimate muscle forces via musculoskeletal modelling. Principle components analysis was used to capture the primary sources of variance from the muscle force waveforms. The magnitude of the forces for the hamstrings, gastrocnemius, and soleus muscles were higher across the majority of stance in male runners regardless of footstrike pattern. Males also demonstrated greater inter-trial variability in the timing of the peak gluteus maximus force and the magnitude of local peaks in the gastrocnemius force waveform. Male and female collegiate cross-country runners appear to employ unique lower extremity muscle force characteristics during overground running.

Surveying the Moral Landscape: How Ethical Frameworks Influence the Structure of Return-to-Sport Decision Making.

SYNOPSIS: Similar to all areas of health care, sports medicine has ethical considerations when making decisions-return to sport being one. Despite a general consensus on criteria to determine when an athlete is ready to return to sport, there are various scenarios that clinicians encounter that may not fall into a clear "yes" or "no" decision. These scenarios leave the clinician asking what is the "right" decision in a given circumstance? A line of questioning that invokes a moral dimension in supporting athletes when they are returning to sport. To address the moral aspect of a clinical decision, ethical frameworks and theories can guide decisions and resolve ethical dilemmas. The aim of this Viewpoint is to briefly describe 4 ethical frameworks and explore how they might apply in a clinical scenario to guide different ethical analyses and influence the final decision. J Orthop Sports Phys Ther 2024;54(4):1-4. Epub 14 February 2024. doi:10.2519/jospt.2024.12310.

Kinematic and muscle force asymmetry in healthy runners: How do different methods measure up?

BACKGROUND: Comparing the performance of one leg to another is a common means of assessing running gait to help inform clinical management strategies. Various methods are employed to quantify asymmetries between limbs. However, limited data is available describing the amount of asymmetry that may be expected during running and no index has been identified as preferable for making a clinical determination of asymmetry. Therefore, this study aimed to describe amounts of asymmetry in collegiate cross-country runners and compare different methods of calculating asymmetry. RESEARCH QUESTION: What can be expected as a normal amount of asymmetry in biomechanical variables in healthy runners when using different indices to quantify limb symmetry? METHODS: Sixty-three (29 male and 34 female) runners participated. Running mechanics were assessed during overground running using 3D motion capture and a musculoskeletal model using static optimization to estimate muscle forces. Independent t-tests were utilized to determine statistical differences in variables between legs. Different methods of quantifying asymmetry were then compared to statistical differences between limbs to determine cut-off values and the sensitivity and specificity of each method. RESULTS: A large portion of runners demonstrated asymmetry during running. Kinematic variables can be expected to have small differences (2-3 degrees) between limbs while muscle forces may show greater amounts of asymmetry. The sensitivities and specificities for each method of calculating asymmetry were similar, however, different methods led to different cut-off values for each variable investigated. SIGNIFICANCE: Asymmetry can be expected between limbs during running. However, when assessing asymmetry, practitioners should consider the joint, variable, and method of calculating asymmetry when determining differences between limbs.

An Updated Model Does Not Reveal Sex Differences in Patellofemoral Joint Stress during Running.

Background: Structure-specific loading may have implications in understanding the mechanisms of running related injury. As females demonstrate a prevalence of patellofemoral pain twice that of males, this may indicate differences in patellofemoral loads between males and females. Previous works investigating differences in patellofemoral joint stress have shown conflicting results, but the models employed have not used estimates of muscle forces or sex specific contact areas. Hypothesis/Purpose: The aim of this study was to examine sex differences in patellofemoral joint stress using an updated model to include estimates of quadriceps muscle force and sex-specific patellofemoral contact area. Study Design: Descriptive Laboratory Study. Methods: Forty-five healthy recreational runners ran at a controlled speed down a 20-meter runway. Kinetic and kinematic data were utilized to estimate muscle forces using static optimization. Quadriceps muscle force was utilized with sex-specific patellofemoral joint contact area in a two-dimensional patellofemoral joint model to estimate patellofemoral joint stress. Multivariate tests were utilized to detect sex differences in patellofemoral loading and hip and knee kinematics. Results: No differences were found between sexes in measures of patellofemoral loading or quadriceps force. Females displayed a reduced knee extension moment and greater hip adduction and internal rotation than males. Conclusion: The inclusion of static optimization to estimate quadriceps muscle force and sex-specific contact area of the patellofemoral joint did not reveal sex differences in patellofemoral joint stress, but differences in non-sagittal plane hip motion were detected. Therefore, two-dimensional patellofemoral models may not fully characterize differences in patellofemoral joint stress between males and females. Three-dimensional patellofemoral models may be necessary to determine if sex differences in patellofemoral joint stress exist. Level of Evidence: 3b.

Sex differences in gluteal muscle forces during running.

Sex differences in common sports injuries to the lower extremity have been reported. Biomechanical factors of the hip have been investigated between sexes with regard to running-related injury. This study investigates gluteal muscle forces between sexes to aid in our understanding of sex-related biomechanical factors in running. Twenty-one healthy male and female runners were participants. Each ran at a controlled speed of 3.52-3.89 m/s down a 20-m runway. Kinetic and kinematic data were utilised to estimate muscle forces. Multivariate analysis of variance tests were utilised to detect differences in gluteal and hamstring muscle forces, hip and pelvic kinematics, and hip kinetic variables between sexes. Males produced greater peak gluteus maximus force, but lesser peak gluteus medius, minimus, and hamstring force than females during running. Males also demonstrated less hip adduction and greater hip flexion and anterior pelvic tilt than females. Finally, males produced lesser peak hip abduction and external rotation moments than females. Males and females demonstrate differences in gluteal muscle forces and hip kinetics and kinematics during running. Further understanding of underlying muscle forces may offer further insight into biomechanical differences in running between males and females.

Biomechanical risk factors for running-related injury differ by sample population: A systematic review and meta-analysis.

BACKGROUND: The role of biomechanical variables of running gait in the development of running related injury has not been clearly elucidated. Several systematic reviews have examined running biomechanics and its association with particular running related injuries. However, due to retrospective designs, inferences into the cause of these injuries are limited. Although prospective studies have been completed, no quantitative analysis pooling these results has been completed. METHODS: A systematic review of MEDLINE, CINAHL, and PubMed was completed. Articles included used prospective study designs, human subjects currently completing a regular running program, and a minimum 12-week follow-up period. Excluded articles had no biomechanical data reported, participants who were beginning runners or military recruits, or had an intervention provided. FINDINGS: Thirteen studies met these criteria. Pooled analyses were completed if two or more studies were available with samples that investigated the same sex and competition level. A qualitative synthesis was completed when pooled analysis was not possible. Five unique running samples were identified and allowed for pooled analyses of variables in mixed-sex collegiate runners and female recreational runners. Moderate evidence exists for increased hip adduction and reduced peak rearfoot eversion as risk factors for running related injury in female recreational runners. Variables differed in other samples of runners. INTERPRETATION: A runner's sex and competition level may affect the relationship between biomechanical factors and the development of running related injury. Hip adduction and rearfoot eversion may be important factors related to running related injury in female recreational runners. Further investigation of biomechanical factors in running injury is warranted.

Relationship among maximum hip isometric strength, hip kinematics, and peak gluteal muscle force during running.

OBJECTIVE: To determine if there is a relationship among isometric hip strength, hip kinematics, and peak gluteal muscle forces in cross-country runners during running. DESIGN: Cross Sectional. SETTING: University Biomechanics Laboratory. PARTICIPANTS: Forty-six NCAA Division III collegiate cross-country runners (18 males, 28 females). MAIN OUTCOME MEASURES: Pearson correlation coefficients were used to describe relationships among isometric hip strength, hip kinematics, and peak gluteal muscle forces during the stance phase of running. Strength of correlations were interpreted as little to no relationship (r < 0.25), fair relationship (0.25 ≤ r < 0.5), moderate relationship (0.5 ≤ r < 0.75), and strong relationship (r ≥ 0.75). Correlations were considered significant if p < 0.05. RESULTS: Little to no relationships were found among isometric hip strength and gluteal muscle forces during running (r < 0.25). A fair relationship was present between prone external rotation isometric hip strength and peak hip adduction (0.25

CLINICAL DECISION MAKING AND TREATMENT IN A RUNNER WITH HIP PAIN AND NEUROMUSCULAR CONTROL DYSFUNCTION: A CASE REPORT.

BACKGROUND AND PURPOSE: The incidence of running related injuries remains high despite numerous efforts to understand the mechanical contributors to the etiology of these injuries. In light of continued running injury, theories of neuromuscular control, or movement patterns, have been suggested as possible contributors to running related injuries. However, the clinical decision making determining when altered neuromuscular control strategies may be affecting a runner's symptoms has not been described. Therefore, the purpose of this case report is to describe the clinical reasoning within the ICF framework for a runner with hip pain and neuromuscular control dysfunction. CASE DESCRIPTION: A 47-year-old, experienced, female runner presented with posterior hip pain and radiating posterior thigh pain limiting her ability to participate in running and threatened her goal to run in an upcoming marathon. Several features of her examination indicated soft tissue muscular irritation of the posterior hip complex related to impaired balance and control of the lower quarter during functional movement and running activities consistent with a neuromuscular control dysfunction. Her initial Focus on Therapeutic Outcomes (FOTO) score was 69 with predicted change score of +7. OUTCOMES: The subject was able to achieve her goals including a return to participation in her weekly running routine and competing in a marathon race. Objective examination features of range of motion, strength, and control of movement were all improved. Her reported function was greatly improved with a final FOTO score 98. DISCUSSION: The diagnosis and treatment of running related injuries remains a clinical challenge. This case report describes the examination and clinical reasoning in diagnosing neuromuscular control dysfunction and proposes a treatment progression to address this functional limitation. The decision making scheme is also structured to follow the International Classification of Functioning, Disability, and Health. LEVEL OF EVIDENCE: 4.

Comparison of two methods of determining patellofemoral joint stress during dynamic activities.

BACKGROUND: Joint specific models rely on muscle force estimates to quantify tissue specific stresses. Traditionally, muscle forces have been estimated using inverse dynamics alone. Inverse dynamics coupled with static optimization techniques allow for an alternative method in estimating muscle forces. Differences between these two techniques have not been compared for determining the quadriceps force for estimating patellofemoral joint stress. METHODS: Eleven female participants completed five squats and ten running trials. Motion capture and force platform data were processed using both solely inverse dynamics and inverse dynamics with static optimization to estimate the quadriceps force in a patellofemoral joint model. FINDINGS: Patellofemoral joint stress calculations were consistently higher when using the combination of inverse dynamics and static optimization as compared to the inverse dynamics alone (p<0.05) yielding estimates that were 30-106% greater. INTERPRETATION: When implementing joint models to estimate tissue specific stresses, the choice of technique used to estimate muscle forces plays an important role in determining the magnitude of estimated stresses in patellofemoral joint models.