Individuals with knee osteoarthritis demonstrate increased passive stiffness of the hip flexor muscles.

BACKGROUND: People with knee osteoarthritis stand and walk with increased trunk flexion. This altered postural alignment increases hamstring activation, elevating mechanical knee loads during walking. Increased hip flexor stiffness may lead to increased trunk flexion. Therefore, this study compared hip flexor stiffness between healthy individuals and individuals with knee osteoarthritis. This study also sought to understand the biomechanical effect of a simple instruction to reduce trunk flexion by 5° during walking. METHODS: Twenty individuals with confirmed knee osteoarthritis and 20 healthy individuals participated. The Thomas test was used to quantity passive stiffness of the hip flexor muscles and three-dimensional motion analysis used to quantify trunk flexion during normal walking. Using a controlled biofeedback protocol, each participant was then instructed to decrease trunk flexion by 5°. RESULTS: Passive stiffness was greater in the group with knee osteoarthritis (effect size = 1.04). For both groups, there was relatively strong correlation between passive stiffness and trunk flexion in walking (r = 0.61-0.72). The instruction to decrease trunk flexion produced only small, non-significant, reductions in hamstring activation during early stance. CONCLUSIONS: This is the first study to demonstrate that individuals with knee osteoarthritis exhibit increased passive stiffness of the hip muscles. This increased stiffness appears to be linked to increased trunk flexion and may therefore underlie the increased hamstring activation which is associated with this disease. As simple postural instruction does not appear to reduce hamstring activity, interventions may be required which can improve postural alignment by reducing passive stiffness of the hip muscles.

Increased trunk flexion may underlie elevated knee flexor activity in people with knee osteoarthritis.

BACKGROUND: Previous research has demonstrated elevated activation of the knee flexor muscles in people with knee osteoarthritis. People with this condition have also been observed to walk with increased trunk flexion; this may alter biomechanical loading patterns and change muscle activation profiles. Therefore, the aim of this study was to understand the biomechanical effect of increasing trunk flexion during walking. METHODS: Kinetic and EMG data were collected from a sample of 20 people with knee osteoarthritis and a sample of 20 healthy matched controls during normal walking. Using a biofeedback protocol, participants were subsequently instructed to walk with a 5° increase in trunk flexion. Sagittal moments, muscle activations and co-contractions were then compared across a window in early stance with a two-way ANOVA test. RESULTS: When trunk flexion was increased, there was a corresponding increase in activity of the medial and lateral hamstrings and gastrocnemius muscles as well as a rise in medial co-contraction. This effect was consistent across the two groups. The most pronounced effect was observed for semitendinosus, which showed a dramatic change in activation profile in the healthy group and a 127% increase in activation during early stance. CONCLUSIONS: This is the first study to demonstrate that increased trunk flexion in people with knee osteoarthritis may explain, to some degree, the elevated knee flexor activity and medial co-contraction which is associated with this disease. These findings motivate further work to understand the therapeutic potential of interventions designed to improve postural alignment.

Comparison of Pelvic Tilt Before and After Hip Flexor Stretching in Healthy Adults.

OBJECTIVE: The purpose of this study was to assess the association between hip flexor length and pelvic tilt or lumbar lordosis by quantifying the effect of stretching on pelvic tilt and lumbar lordosis. METHODS: We quantified pelvic tilt and lumbar lordosis before and after a single session of passive hip flexor stretching in a sample of 23 male participants. Changes in hip flexor length were also characterized, using a Thomas test protocol to measure passive hip extension in supine lying. We investigated both the mean effect of the stretching protocol and potential correlations between changes in passive hip extension and changes in pelvic tilt or lumbar lordosis. RESULTS: Following the stretching protocol, there was a mean increase of 2.6° (P < .001) in passive hip extension and a corresponding mean reduction of 1.2° (P < .001) in anterior pelvic tilt. However, there was no change in lumbar lordosis, nor were there any meaningful correlations between change in passive hip extension and change in pelvic tilt or lumbar lordosis. CONCLUSION: The results suggest that hip muscle stretching may lead to immediate reductions in pelvic tilt during relaxed standing. Such stretching programs could play an important role in interventions designed to improve standing postural alignment.

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 whether male runners with a history of repeat calf muscle strain injury demonstrate differences in stance phase running kinematics when compared to healthy controls. STUDY DESIGN: Case-control investigation. LEVEL OF EVIDENCE: 3b. 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 2.1° and 3.1° 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.

A new integrated behavioural intervention for knee osteoarthritis: development and pilot study.

BACKGROUND: Exercise-based approaches have been a cornerstone of physiotherapy management of knee osteoarthritis for many years. However, clinical effects are considered small to modest and the need for continued adherence identified as a barrier to clinical efficacy. While exercise-based approaches focus on muscle strengthening, biomechanical research has identified that people with knee osteoarthritis over activate their muscles during functional tasks. Therefore, we aimed to create a new behavioural intervention, which integrated psychologically informed practice with biofeedback training to reduce muscle overactivity, and which was suitable for delivery by a physiotherapist. METHODS: Through literature review, we created a framework linking theory from pain science with emerging biomechanical concepts related to overactivity of the knee muscles. Using recognised behaviour change theory, we then mapped a set of intervention components which were iteratively developed through ongoing testing and consultation with patients and physiotherapists. RESULTS: The underlying framework incorporated ideas related to central sensitisation, motor responses to pain and also focused on the idea that increased knee muscle overactivity could result from postural compensation. Building on these ideas, we created an intervention with five components: making sense of pain, general relaxation, postural deconstruction, responding differently to pain and functional muscle retraining. The intervention incorporated a range of animated instructional videos to communicate concepts related to pain and biomechanical theory and also used EMG biofeedback to facilitate visualization of muscle patterns. User feedback was positive with patients describing the intervention as enabling them to "create a new normal" and to be "in control of their own treatment." Furthermore, large reductions in pain were observed from 11 patients who received a prototype version of the intervention. CONCLUSION: We have created a new intervention for knee osteoarthritis, designed to empower individuals with capability and motivation to change muscle activation patterns and beliefs associated with pain. We refer to this intervention as Cognitive Muscular Therapy. Preliminary feedback and clinical indications are positive, motivating future large-scale trials to understand potential efficacy. It is possible that this new approach could bring about improvements in the pain associated with knee osteoarthritis without the need for continued adherence to muscle strengthening programmes. TRIAL REGISTRATION: ISRCTN51913166 (Registered 24-02-2020, Retrospectively registered).

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 3.2 m/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, 0.6°- 2.6°; MDC, 1.5°- 7.2) and peak angles during stance (Range: ICC, 0.799 - 0.946; SEM, 0.6°- 2.6°; MDC, 1.7°- 7.1°). Peak transverse plane kinematics of the hip (ICC, 0.783; SEM, 3.2°; MDC, 8.7°) and knee (ICC, 0.739; SEM, 3°; MDC, 8.4°) 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, 0.8°- 5.7°; MDC, 2.5°- 15.7°). 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.

Prolonged sitting and physical inactivity are associated with limited hip extension: A cross-sectional study.

BACKGROUND: It is possible that physical inactivity and prolonged sitting could lead to changes in muscle properties or bony limitations which may reduce passive hip extension. OBJECTIVES: This study explored the association between passive hip extension and sitting/physical activity patterns. DESIGN: Cross sectional study. METHOD: The modified Thomas Test is a clinical test used to characterise hip flexion contracture. This test was used to measure passive hip extension across 144 individuals. In addition, sitting behaviours and physical activity patterns were quantified using the Global Physical Activity Questionnaire. Cut off points were defined for low/high physical activity (150 min per week), prolonged sitting (>7 h per day) and minimal sitting (<4 h per day). ANOVA testing was then used to compare passive hip extension between three groups, defined using the specified thresholds: low activity & prolonged sitting, high activity & minimal sitting and high activity & prolonged sitting. RESULTS: A total of 98 participants were allocated to one of the three groups which were shown to differ significantly in passive hip extension (P < 0.001). Importantly, there was 6.1° more passive hip extension in the high activity & minimal sitting group when compared to the low activity & prolonged sitting group. CONCLUSION: This study is the first to demonstrate an association between passive hip extension and prolonged sitting/physical inactivity. It is possible that these findings indicate a physiological adaptation in passive muscle stiffness. Further research is required to understand whether such adaptation may play a role in the aetiology of musculoskeletal pain linked to prolonged sitting.

The effect of increasing trunk flexion during normal walking.

BACKGROUND: The head, arms and trunk segment constitute a large proportion of the body's mass. Therefore, small alterations in trunk inclination may affect lower limb joint moments and muscle activation patterns. Although previous research has investigated the effect of changing frontal plane inclination of the trunk, it is not clear how increasing trunk flexion will impact on the activation of the lower limb muscles. RESEARCH QUESTION: What is the effect of independently manipulating trunk flexion angle on lower limb kinematics, moments and muscle function? METHODS: Gait analysis was carried out on 20 healthy people under four trunk flexion conditions: normal walking (NW), NW-5°, NW+5° and NW+10°. For the latter three conditions, a biofeedback approach was used to tightly control trunk flexion angle. A linear mixed model was used to investigate the effect of changing trunk flexion on joint angles, moments, and knee muscle activation. RESULTS: There were clear increases in hip and ankle moments as trunk flexion was increased, but no change in knee moments. The results also showed a linear increase in knee flexor muscle activity and a corresponding increase in co-contraction as trunk flexion increased. Interestingly, there was a dramatic change in the profile of hamstring activity. In the medial hamstrings, this change led to a 100% increase in activation during early stance as flexion was increased by 5° from NW. SIGNIFICANCE: This is the first study to demonstrate a strong dependence of knee flexor muscle activity on trunk flexion. This is important as people with knee osteoarthritis have been observed to walk with elevated muscle activation and this has been linked to increased joint loads. It is possible that these altered muscle patterns may result from increased trunk flexion during walking.

Between-day repeatability of lower limb EMG measurement during running and walking.

There are minimal data describing the between-day repeatability of EMG measurements during running. Furthermore, there are no data characterising the repeatability of surface EMG measurement from the adductor muscles, during running or walking. The purpose of this study was to report on the consistency of EMG measurement for both running and walking across a comprehensive set of lower limb muscles, including adductor magnus, longus and gracilis. Data were collected from 12 lower limb muscles during overground running and walking on two separate days. The coefficient of multiple correlation (CMC) was used to quantify waveform similarity across the two sessions for signals normalised to either maximal voluntary isometric contraction (MVIC) or mean/peak signal magnitude. For running, the data showed good or excellent repeatability (CMC = 0.87-0.96) for all muscles apart from gracilis and biceps femoris using the MVIC method. Similar levels of repeatability were observed for walking. Importantly, using the peak/mean method as an alternative to the MVIC method, resulted in only marginal improvements in repeatability. The proposed protocol facilitated the collection of repeatable EMG data during running and walking and therefore could be used in future studies investigating muscle patterns during gait.

Could Relative Movement Between the Adductor Muscles and the Skin Invalidate Surface Electromyography Measurement?

The superficial hip adductor muscles are situated in close proximity to each other. Therefore, relative movement between the overlying skin and the muscle belly could lead to a shift in the position of surface electromyography (EMG) electrodes and contamination of EMG signals with activity from neighboring muscles. The aim of this study was to explore whether hip movements or isometric contraction could lead to relative movement between the overlying skin and 3 adductor muscles: adductor magnus, adductor longus, and adductor gracilis. The authors also sought to investigate isometric torque-EMG relationships for the 3 adductor muscles. Ultrasound measurement showed that EMG electrodes maintained a position which was at least 5 mm within the muscle boundary across a range of hip flexion-extension angles and across different contraction levels. The authors also observed a linear relationship between torque and EMG amplitude. This is the first study to use ultrasound to track the relative motion between skin and muscle and provides new insight into electrode positioning. The findings provide confidence that ultrasound-based positioning of EMG electrodes can be used to derive meaningful information on output from the adductor muscles and constitute a step toward recognized guidelines for surface EMG measurement of the adductors.

Using the spring-mass model for running: Force-length curves and foot-strike patterns.

BACKGROUND: The spring-mass model is commonly used to investigate the mechanical characteristics of human running. Underlying this model is the assumption of a linear force-length relationship, during the stance phase of running, and the idea that stiffness can be characterised using a single spring constant. However, it remains unclear whether the assumption of linearity is valid across different running styles. RESEARCH QUESTION: How does the linearity of the force-length curve vary across a sample of runners and is there an association between force-length linearity and foot-strike index/speed? METHODS: Kinematic and kinetic data were collected from twenty-eight participants who ran overground at four speeds. The square of the Pearson's correlation coefficient, R2, was used to quantify linearity; with a threshold of R2 ≥ 0.95 selected to define linear behaviour. A linear mixed model was used to investigate the association between linearity and foot-strike index and speed. RESULTS: Only 36-46 % of participants demonstrated linear force-length behaviour across the four speeds during the loading phase. Importantly, the linear model showed a significant effect of both foot-strike index and speed on linearity during the loading phase (p = 0.003 and p < 0.001, respectively). SIGNIFICANCE: This study showed that the assumption of a linear force-length relationship is not appropriate for all runners. These findings suggest that the use of the spring-mass model, and a constant value of stiffness, may not be appropriate for characterising and comparing different running styles. Given these findings, it may be better to restrict the use of the spring-mass model to individuals who exhibit linear force-length dependence. It would also be appropriate for future studies, characterising stiffness using the spring-mass model, to report data on force-length linearity across the cohort under study.

How does normal variability in trunk flexion affect lower limb muscle activity during walking?

A large proportion of the mass of the body is contained within the trunk segment. Therefore, small changes in the inclination of this segment have the potential to influence the direction of the ground reaction force and alter lower limb joint moments and muscle activation patterns during walking. The aim of this study was to investigate if variability in sagittal trunk inclination in healthy participants is associated with differences in lower limb biomechanics. Gait analysis data was collected on 41 healthy participants during walking. Two groups were defined based on habitual trunk flexion angle during normal walking, a forward lean group (n = 18) and a backward lean group (n = 17). Lower limb moments, muscle activation patterns and co-contraction levels were compared between the two groups using independent t-tests. The forward lean group walked with 5° more trunk flexion than the backward lean group. This difference was associated with a larger peak hip moment (effect size = 0.7) and higher activation of the lateral gastrocnemius (effect size =0.6) and the biceps femoris (effect size =0.7) muscles. The forward lean group also exhibited greater co-contraction in late stance (effect size =0.7). This is the first study to demonstrate that small differences in trunk flexion are associated with pronounced alterations in the activation of the lateral knee flexor muscles. This is important because people with knee osteoarthritis have been observed to walk with increased trunk flexion. It is possible that increased sagittal trunk inclination may be associated with elevated joint loads in people with knee osteoarthritis.

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: To investigate whether a 10% increase in the 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; Level of evidence, 4. METHODS: Runners with PFP underwent a 3-dimensional gait analysis to confirm the presence of aberrant frontal-plane hip and/or pelvis kinematics at baseline. A total of 12 participants with frontal-plane hip and/or pelvis kinematics 1 standard deviation above a reference database were invited to undergo the gait retraining intervention. Running kinematics along with clinical outcomes of pain and functional outcomes were recorded at baseline, 4 weeks after 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 smartwatch and audible metronome. RESULTS: After gait retraining, significant improvements in running kinematics and clinical outcomes were observed at 4-week and 3-month follow-up. Repeated-measures analysis of variance with post hoc Bonferroni correction (P < .016) showed significant reductions in peak contralateral pelvic drop (mean difference [MD], 3.12° [95% CI, 1.88°-4.37°]), hip adduction (MD, 3.99° [95% CI, 2.01°-5.96°]), and knee flexion (MD, 4.09° [95% CI, 0.04°-8.15°]) as well as significant increases in self-reported weekly running volume (MD, 13.78 km [95% CI, 4.62-22.93 km]) and longest run pain-free (MD, 6.84 km [95% CI, 3.05-10.62 km]). Friedman test with a post hoc Wilcoxon signed-rank test showed significant improvements on a numerical rating scale for worst pain in the past week and the Lower Extremity Functional Scale. CONCLUSION: A single session of gait retraining using a 10% increase in step rate resulted 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 that gait interventions are targeted appropriately. REGISTRATION: NCT03067545 (ClinicalTrials.gov identifier).

Trunk flexion during walking in people with knee osteoarthritis.

BACKGROUND: Over 50% of the body's mass is concentrated within the head, arms and trunk. Thus, small deviations in the orientation of the trunk, during normal walking, could influence the position of the centre of mass relative to the lower limb joint centres and impact on lower limb biomechanics. However, there are minimal data available on sagittal kinematics of the trunk in people with knee osteoarthritis (OA) during walking. RESEARCH QUESTION: Do people with knee OA have altered kinematic patterns of the trunk, pelvis or hip compared with healthy control participants during walking? METHODS: Statistical parametric mapping was used to compare sagittal and frontal plane kinematic patterns, during walking, between a healthy group and cohort of people with knee OA. RESULTS: Individuals with knee OA walked with a mean increase in trunk flexion of 2.6°. Although this difference was more pronounced during early stance, it was maintained across the whole of stance phase. There were no differences, between the groups, in sagittal plane pelvic or hip kinematics. There were also no differences in trunk, pelvic or hip kinematics in the frontal plane. SIGNIFICANCE: Most previous gait research investigating trunk motion in people with knee OA has focused on the frontal plane. However, our data suggest that an increase in sagittal trunk flexion may be a clinical hallmark of people with this disease. Altered trunk flexion could affect joint moments and muscle patterns and therefore our results motivate further research in this area.

The biomechanical characteristics of high-performance endurance running.

The biomechanical profile of high-level endurance runners may represent a useful model that could be used for developing training programmes designed to improve running style. This study, therefore, sought to compare the biomechanical characteristics of high-performance and recreational runners. Kinematic and kinetic measurements were taken during overground running from a cohort of 14 high-performance (8 male) and 14 recreational (8 male) runners, at four speeds ranging from 3.3 to 5.6 m s-1. Two-way ANOVA analysis was then used to explore group and speed effects and principal component analysis used to explore the interdependence of the tested variables. The data showed the high-performance runners to have a gait style characterised by an increased vertical velocity of the centre of mass and a flight time that was 11% longer than the recreational group. The high-performance group were also observed to adopt a forefoot strike pattern, to contact the ground with their foot closer to their body and to have a larger ankle moment. Importantly, although observed group differences were mostly independent of speed, the tested variables showed a high degree of interdependence suggesting an underlying unitary phenomenon. This is the first study to compare high-performance and recreational runners across a full range of kinematic and kinetic variables. The results suggest that high-performance runners maintain stride length with a prolonged aerial phase, rather than by landing with a more extended knee. These findings motivate future intervention studies that should investigate whether recreational runners could benefit from instruction to decrease shank inclination at foot contact.

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 injuries. HYPOTHESIS: Injured runners will demonstrate differences in running kinematics when compared with injury-free controls. These kinematic patterns will be consistent among injured subgroups. STUDY DESIGN: Controlled laboratory study. METHODS: The authors studied 72 injured runners and 36 healthy controls. The injured group contained 4 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 4 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 (CPD) and forward trunk lean at midstance and a more extended knee and dorsiflexed ankle at initial contact. The subgroup analysis of variance found that these kinematic patterns were consistent across each of the 4 injured subgroups. CPD was found to be the most important variable predicting the classification of participants as healthy or injured. Importantly, for every 1° increase in pelvic drop, there was an 80% increase in the odds of being classified as 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 CPD and trunk forward lean as well as an extended knee and dorsiflexed ankle at initial contact. CPD 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.

Optimisation of rocker sole footwear for prevention of first plantar ulcer: comparison of group-optimised and individually-selected footwear designs.

BACKGROUND: Appropriate footwear for individuals with diabetes but no ulceration history could reduce the risk of first ulceration. However, individuals who deem themselves at low risk are unlikely to seek out bespoke footwear which is personalised. Therefore, our primary aim was to investigate whether group-optimised footwear designs, which could be prefabricated and delivered in a retail setting, could achieve appropriate pressure reduction, or whether footwear selection must be on a patient-by-patient basis. A second aim was to compare responses to footwear design between healthy participants and people with diabetes in order to understand the transferability of previous footwear research, performed in healthy populations. METHODS: Plantar pressures were recorded from 102 individuals with diabetes, considered at low risk of ulceration. This cohort included 17 individuals with peripheral neuropathy. We also collected data from 66 healthy controls. Each participant walked in 8 rocker shoe designs (4 apex positions × 2 rocker angles). ANOVA analysis was then used to understand the effect of two design features and descriptive statistics used to identify the group-optimised design. Using 200 kPa as a target, this group-optimised design was then compared to the design identified as the best for each participant (using plantar pressure data). RESULTS: Peak plantar pressure increased significantly as apex position was moved distally and rocker angle reduced (p < 0.001). The group-optimised design incorporated an apex at 52% of shoe length, a 20° rocker angle and an apex angle of 95°. With this design 71-81% of peak pressures were below the 200 kPa threshold, both in the full cohort of individuals with diabetes and also in the neuropathic subgroup. Importantly, only small increases (<5%) in this proportion were observed when participants wore footwear which was individually selected. In terms of optimised footwear designs, healthy participants demonstrated the same response as participants with diabetes, despite having lower plantar pressures. CONCLUSIONS: This is the first study demonstrating that a group-optimised, generic rocker shoe might perform almost as well as footwear selected on a patient by patient basis in a low risk patient group. This work provides a starting point for clinical evaluation of generic versus personalised pressure reducing footwear.

Large Scale Population Assessment of Physical Activity Using Wrist Worn Accelerometers: The UK Biobank Study.

BACKGROUND: Physical activity has not been objectively measured in prospective cohorts with sufficiently large numbers to reliably detect associations with multiple health outcomes. Technological advances now make this possible. We describe the methods used to collect and analyse accelerometer measured physical activity in over 100,000 participants of the UK Biobank study, and report variation by age, sex, day, time of day, and season. METHODS: Participants were approached by email to wear a wrist-worn accelerometer for seven days that was posted to them. Physical activity information was extracted from 100Hz raw triaxial acceleration data after calibration, removal of gravity and sensor noise, and identification of wear / non-wear episodes. We report age- and sex-specific wear-time compliance and accelerometer measured physical activity, overall and by hour-of-day, week-weekend day and season. RESULTS: 103,712 datasets were received (44.8% response), with a median wear-time of 6.9 days (IQR:6.5-7.0). 96,600 participants (93.3%) provided valid data for physical activity analyses. Vector magnitude, a proxy for overall physical activity, was 7.5% (2.35mg) lower per decade of age (Cohen's d = 0.9). Women had a higher vector magnitude than men, apart from those aged 45-54yrs. There were major differences in vector magnitude by time of day (d = 0.66). Vector magnitude differences between week and weekend days (d = 0.12 for men, d = 0.09 for women) and between seasons (d = 0.27 for men, d = 0.15 for women) were small. CONCLUSIONS: It is feasible to collect and analyse objective physical activity data in large studies. The summary measure of overall physical activity is lower in older participants and age-related differences in activity are most prominent in the afternoon and evening. This work lays the foundation for studies of physical activity and its health consequences. Our summary variables are part of the UK Biobank dataset and can be used by researchers as exposures, confounding factors or outcome variables in future analyses.

Are the arms and head required to accurately estimate centre of mass motion during running?

Accurate measurement of centre of mass (CoM) motion can provide valuable insight into the biomechanics of human running. However, full-body kinematic measurement protocols can be time consuming and difficult to implement. Therefore, this study was performed to understand whether CoM motion during running could be estimated from a model incorporating only lower extremity, pelvic and trunk segments. Full-body kinematic data was collected whilst (n=12) participants ran on a treadmill at two speeds (3.1 and 3.9ms-1). CoM trajectories from a full-body model (16-segments) were compared to those estimated from a reduced model (excluding the head and arms). The data showed that, provided an offset was included, it was possible to accurately estimate CoM trajectory in both the anterior-posterior and vertical direction, with root mean square errors of 5mm in both directions and close matches in waveform similarity (r=0.975-1.000). However, in the ML direction, there was a considerable difference in the CoM trajectories of the two models (r=0.774-0.767). This finding suggests that a full-body model is required if CoM motions are to be measured in the ML direction. The mismatch between the reduced and full-body model highlights the important contribution of the arms to CoM motion in the ML direction. We suggest that this control strategy, of using the arms rather than the heavier trunk segments to generate CoM motion, may lead to less variability in CoM motion in the ML direction and subsequently less variability in step width during human running.