Is there a minimum complexity required for the biomechanical modelling of running?

Mathematical models have the potential to provide insight into human running. Existing models can be categorised as either simple or complex, and there appears to be a lack of natural progression in model development. By sequentially adding complexity, there is the potential to determine how different mechanical components contribute to the biomechanics of running. In this study, a series of four models, of increasing complexity were developed in OpenSim: a simple spring-mass model, a two-segment model with a torsional spring at the knee and two three-segment models, one with a sprung knee and ankle and another with a sprung knee and actuated ankle. For each model, a forward simulation was developed and model predictions compared with experimental data from 10 forefoot runners. The results showed the spring-mass model overestimated the vertical displacement of the centre of mass (percentage difference: 43.6(22.4)-67.7(21.7)%) and underestimated the vertical ground reaction force (percentage difference: 13.7(8.9)-34.4(10.9)%) compared to the experimental data. Adding a spring at the knee increased the match with the vertical centre of mass displacement (percentage difference: 4.4(25.2)-18.4(40.2)%), however, geometry restrictions meant it was only possible to model approximately 60% of stance. The passive three-segment model showed a good match with centre of mass movements across most of stance (percentage difference in the vertical centre of mass displacement: 4.3(24.5)-21.3(19.2)%), however, actuation at the ankle was required to obtain a closer match with experimental kinetics and joint trajectories (e.g. vertical ground reaction force RMSD decreased by approximately 0.4BW). This is the first study to investigate models of increasing complexity of distance running. The results show that agreement between experimental data and model simulations improves as complexity increases and this provides useful insight into the mechanics of human running

A 10% increase in step rate improves running kinematics and clinical outcomes in runners with patellofemoral pain at 4 weeks and 3 months

Background: Aberrant frontal plane hip and pelvis kinematics have been frequently observed in runners with patellofemoral pain (PFP). Gait retaining interventions have been shown to improve running kinematics and may therefore be beneficial in runners with PFP. Purpose: the aim of this study was to investigate whether a 10% increase in running step rate influences frontal plane kinematics of the hip and pelvis, as well as clinical outcomes in runners with PFP. Study Design: Case Series Methods: Runners with PFP underwent a 3D gait analysis to confirm the presence of aberrant frontal plane hip and pelvis kinematics at baseline. Twelve participants with frontal plane hip and pelvis kinematics one standard deviation above a reference database, were invited to participate in the gait retraining intervention. Running kinematics along with clinical outcomes of pain and functional measures were recorded at baseline, 4 weeks following retraining and 3-months. Gait retraining consisted of a single session where step rate was increased by 10% using an audible metronome. Participants were asked to continue their normal running while self-monitoring their step rate using a global positioning system watch and audible metronome. Results: Following gait retraining significant improvements in running kinematics and clinical outcomes were observed at 4 week and 3-month follow up. Repeated measures ANOVA with post hoc Bonferroni (p <0.016) showed significant reductions in peak contralateral pelvic drop (Mean Difference [MD], 3.12⁰; 95% Confidence Interval [CI], 1.88⁰, 4.37⁰), hip adduction (MD, 3.99⁰; 95% CI, 2.01⁰, 5.96⁰) and knee flexion (MD, 4.09⁰; 95% CI, 0.04⁰, 8.15⁰), as well as significant increases in self-reported weekly running volume (MD, -13.78km; 95% CI, -22.93km, -4.62km) and longest run pain free (MD, -6.84km; 95% CI, -10.62km, -3.05km). Friedman test with post hoc Wilcoxon signed-rank showed significant improvements in Numerical Rating Scale for worst pain in the past week and Lower Extremity Functional Scale. Conclusion: A single session of gait retraining using a 10% increase in step rate results in significant improvements in running kinematics, pain and function in runners with PFP. These improvements were maintained at 3-month follow up. It is important to assess for aberrant running kinematics at baseline to ensure gait interventions are targeted appropriately. Clinical Relevance: Step rate modification is a simple method of gait retraining that can be easily integrated into clinical practice and running outside of a laboratory setting

Is there a pathological gait associated with common soft tissue running injuries?

Background: Previous research has demonstrated clear associations between specific running injuries and patterns of lower limb kinematics. However, there has been minimal research investigating whether the same kinematic patterns could underlie multiple different soft tissue running injuries. If they do, such kinematic patterns could be considered global contributors to running injury. Hypothesis: Injured runners will demonstrate differences in running kinematics when compared to injury free controls. These kinematic patterns will be consistent amongst injury subgroups. Study Design: Case- Control Study Methods: We studied 72 injured runners and 36 healthy controls. The injured group contained four subgroups of runners with either patellofemoral pain, iliotibial band syndrome, medial tibial stress syndrome or Achilles tendinopathy (n = 18 each). Three-dimensional running kinematics were compared between injured and healthy runners and then between the four injured subgroups. A logistic regression model was used to determine which parameters could be used to identify injured runners. Results: The injured runners demonstrated greater contralateral pelvic drop and forward trunk lean at mid-stance and a more extended knee and dorsiflexed ankle at initial contact. The subgroup ANOVA found these kinematic patterns were consistent across each of the four injury subgroups. Contralateral pelvic drop was found to be the most important variable predicting classification of participants as healthy/injured. Importantly, for every 1° increase in pelvic drop there was an 80% increase in the odds of being classified injured. Conclusion: This study identified a number of global kinematic contributors to common running injuries. In particular, we found injured runners to run with greater peak contralateral pelvic drop and trunk forward lean, as well as an extended knee and dorsiflexed ankle at initial contact. Contralateral pelvic drop appears to be the variable most strongly associated with common running related injuries. Clinical Relevance: The identified kinematic patterns may prove beneficial for clinicians when assessing for biomechanical contributors to running injuries

Let’s take the dog for a gait…

Background In 1872, Eadweard Muybridge was hired to research unsupported transit in horses, i.e. the trot and the gallop. This research was the first instance of the use of photography to analyse movement and was the ultimate precursor to motion capture for biomechanical assessment of movement utilised today. With the expansion of the field continuing, the term “gait” has become synonymous with walking and is often used interchangeably. In this editorial, we discuss the term “gait” and its’ origin in the context of scientific research and aim to address the heterogeneous taxonomy associated with the ambiguous use of the term “gait”. Research question What is the ambiguous use of the term gait? Methods A non-systematic review was conducted of the original research and short communications in the 2019 issues of Gait and Posture Results A total of 219 titles were characterised as directly addressing locomotion. Of these, a total of 108 titles quantified the form of locomotion (e.g. walk/ing, run/ing) and 111 titles utilised the word “gait” to describe the task. However, 104 of these clarified the form of locomotion either within the abstract or the main text of the manuscript. Significance “Gait” is not mutually exclusive to humans nor walking. The ambiguity associated with the use of this term demonstrates the importance of quantifying the type of locomotion being studied. Ultimately, such efforts will allow the streamlining search strategies for appropriate research for academics, clinicians, and scientists alike

Kinematic characteristics of male runners with a history of recurrent calf muscle strain injury

Background: Calf muscle strain injuries are a common running injury affecting male runners and are known to have high reoccurrence rates. Currently, limited evidence exists investigating factors associated with this injury with no previous study investigating the running kinematics of male runners with a history of repeat calf muscle strain injuries. Purpose: To investigate differences in running kinematics between runners with a history of recurrent calf muscle strain injury and injury free controls. Study Design: Case-control investigation Level of Evidence: 4 Methods: Stance phase kinematics were compared between 15 male runners with a history of calf muscle strain injury and 15 male control participants during treadmill running at 3.2m/s. Independent t-tests were used to compare differences in stance phase kinematic parameters between groups and effect sizes were calculated using Cohen’s d. Results: The group with a history of calf muscle strain injury demonstrated a significant 2.1⁰ and 3.1⁰ increase in contralateral pelvic drop and anterior pelvic tilt during mid stance. In addition, this group exhibited longer stance times and a more anterior tilted pelvis, flexed hip and a greater distance between the heel and centre of mass at initial contact. Large effect sizes, greater than 0.8, were observed for all differences. No significant differences were observed for ankle and knee joint kinematics between the groups. Conclusion: This is the first study to identify kinematic characteristics associated with recurrent calf muscle strain injury. While it is not possible to determine causality, the observed kinematic differences may contribute to recurrent nature of this injury. Specifically, it is possible that neuromuscular deficits of the hip and calf muscle complex may lead to increased strain on the calf complex. Rehabilitation interventions which focus on addressing pelvis and hip kinematics may reduce the demands placed upon the calf complex and could prove clinically effective

The between-day repeatability, standard error of measurement and minimal detectable change for discrete kinematic parameters during treadmill running

Background: Kinematic parameters of the trunk, pelvis and lower limbs are frequently associated with both running injuries and performance, and the target of clinical interventions. Currently there is limited evidence reporting the between-day repeatability of discrete kinematic parameters of the trunk, pelvis and lower limbs during treadmill running. Research question: What is the between-day repeatability, standard error of measurement and minimal detectable change of discrete kinematic parameters of the trunk, pelvis and lower limbs during treadmill running? Methods: 16 healthy participants attended two kinematic data collection sessions two weeks apart. Three-dimensional kinematic data were collected while participants ran on a motorised treadmill at 3.2m/s. The interclass correlation coefficient, standard error of measurement and minimal detectable change were calculated for discrete kinematic parameters at initial contact, toe off, peak angles and joint excursions during the stance phase of running. Results: Good to excellent repeatability with low standard error of measurement and minimal detectable change values were observed for sagittal and frontal plane kinematics at initial contact (Range: ICC, 0.829 - 0.941; SEM, 0.6⁰- 2.6⁰; MDC, 1.5⁰- 7.2) and peak angles during stance (Range: ICC, 0.799 – 0.946; SEM, 0.6⁰- 2.6⁰; MDC, 1.7⁰- 7.1⁰). Peak transverse plane kinematics of the hip (ICC, 0.783; SEM, 3.2⁰; MDC, 8.7⁰) and knee (ICC, 0.739; SEM, 3⁰; MDC, 8.4⁰) demonstrated moderate between-day repeatability with large SEM and MDC values. Kinematics at toe off demonstrated the lowest ICC values and largest measurement errors of all parameters (Range: ICC, 0.109 – 0.900; SEM, 0.8⁰- 5.7⁰; MDC, 2.5⁰- 15.7⁰). Significance: This is the first study detailing the measurement error and minimal detectable change for discrete kinematic parameters of the trunk and pelvis during treadmill running. The reported values may provide a useful reference point for future studies investigating between-day differences in running kinematics

The effect of sex, stature, and limb length on the preferred walk-to-run transition speed

Background The preferred walk-to-run transition speed (PTS) for healthy adults is approximately 2 m∙s-1, however, PTS is influenced by anthropometric factors. Yet despite known sex differences in anthropometrics, studies have reported no sex differences in PTS. Research question Do stature and limb length affect PTS in the same way for both male and female healthy adults? Methods Thirty-seven (19 female) non-injured adults volunteered for this study. Participants completed a walk-to-run transition protocol, where the treadmill speed was increased from 1.2 m∙s-1 to 2.2 m∙s-1, in increments of 0.1 m∙s-1 every two minutes. An independent t-test compared PTS between sexes. Multiple regression analysis determined the effect of sex and stature and sex and limb length on PTS. Results Female participants transitioned at a lower PTS than male participants (1.8 (0.2) m∙s-1 versus 1.9 (0.1) m∙s-1; p ≤ 0.026). Sex and stature explained 19% of the variance in PTS, while sex and limb length explained 21% of the variance. Including interactions increased the variance explained by 23% and 2% for sex and stature and sex and limb length, respectively. The significant interaction between sex and stature showed PTS was inversely proportional to stature for male participants but directly proportional for female participants. Significance These findings suggest that the extent to which stature and limb length influence the preferred transition speed may differ between sexes

Cross-sectional analysis of educational inequalities in primary prevention statin use in UK Biobank.

OBJECTIVE: Identify whether participants with lower education are less likely to report taking statins for primary cardiovascular prevention than those with higher education, but an equivalent increase in underlying cardiovascular risk. METHODS: Using data from a large prospective cohort study, UK Biobank, we calculated a QRISK3 cardiovascular risk score for 472 097 eligible participants with complete data on self-reported educational attainment and statin use (55% female participants; mean age 56 years). We used logistic regression to explore the association between (i) QRISK3 score and (ii) educational attainment on self-reported statin use. We then stratified the association between QRISK3 score and statin use, by educational attainment to test for interactions. RESULTS: There was evidence of an interaction between QRISK3 score and educational attainment. Per unit increase in QRISK3 score, more educated individuals were more likely to report taking statins. In women with ≤7 years of schooling, a one unit increase in QRISK3 score was associated with a 7% higher odds of statin use (OR 1.07, 95% CI 1.07 to 1.07). In women with ≥20 years of schooling, a one unit increase in QRISK3 score was associated with an 14% higher odds of statin use (OR 1.14, 95% CI 1.14 to 1.15). Comparable ORs in men were 1.04 (95% CI 1.04 to 1.05) for ≤7 years of schooling and 1.08 (95% CI 1.08, 1.08) for ≥20 years of schooling. CONCLUSION: Per unit increase in QRISK3 score, individuals with lower educational attainment were less likely to report using statins, likely contributing to health inequalities