'A whole different ball game': the qualitative experience of older adults with a transtibial amputation and the use of a self-aligning prosthetic ankle-foot on the STEPFORWARD trial.

BACKGROUND: Older patients with lower limb amputation, categorised as having "limited community mobility", are under-researched. Understanding their experience with a new prosthetic ankle-foot is important when designing clinical trials. The aim of this qualitative study was to explore the adjustments they made after amputation and the acceptability of a self-aligning ankle-foot (SA-AF) to older adults. METHODS: Fourteen participants, who took part in the STEPFORWARD randomised controlled feasibility trial (ISRCTN15043643), were purposively recruited; nine were intervention participants and five were standard care participants. They were asked to reflect on their life prior to and consider the adjustments they made following their amputation. Participants in the intervention group were also asked about their views of the new SA-AF compared to their standard non-SA-AF. A thematic analysis was undertaken. RESULTS: Three broad themes were identified: The impact of the amputation; Role of clinical support; and Experiences of the SA-AF. The findings tell a narrative of the long-term impact that amputation has on these individuals' lives. Participants randomised to receive the SA-AF were very positive about it, reporting less pain, greater mobility and being able to do more. CONCLUSION: Participants who used the SA-AF found it an acceptable intervention. These findings suggest that a full-scale RCT is warranted.

There is a high degree of acceptability among an older patient group with a transtibial amputation to use a self-aligning ankle foot.Patients reported experiencing better mobility and more prosthetic comfort with the self-aligning ankle-foot.Key outcomes important to participants include engagement in social and daily activities and balance confidence.

Attempted symmetry affects dynamic gait stability in individuals with lower-limb amputation.

BACKGROUND: Gait in people with lower limb amputation (LLA) is typically asymmetrical. Reducing this asymmetry is often attempted to minimise the impact of secondary health issues. However, temporal-spatial asymmetry in gait of people with LLA has also been shown to underpin dynamic stability. RESEARCH QUESTION: The current study aimed to identify the effects of acute attempts to achieve temporal-spatial symmetry on the dynamic stability of people with unilateral transtibial amputation (UTA). The secondary aim of this study was to identify the corresponding biomechanical adaptations during attempted symmetrical gait. METHODS: Eleven people with UTA walked along a 15 m walkway in four different conditions: normal (NORM), attempted symmetrical step length and step frequency (SYMSL+SF) attempted symmetrical step length (SYMSL) and attempted symmetrical step frequency (SYMSF). Dynamic stability was measured using the backward (BW) and medio-lateral (ML) margins of stability (MoS). RESULTS: Results indicate that attempting SYMSF had a positive effect on gait stability in BW and ML directions, while attempting SYMSL had a potentially negative effect, although these results did not appear to be significant. The absence of clustering in principal component analysis, supported the lack of significant results, indicating no features differentiating between conditions of attempted symmetry. Conversely, there was clustering by limbs which were associated with differences in knee and ankle joint angles between the prosthetic and non-prosthetic limbs, and clustering by individuals highlighting the importance of patient-specific analysis. CONCLUSION: The data suggests that attempted symmetrical gait reduces asymmetry but also affects dynamic stability.

Using Lower Limb Wearable Sensors to Identify Gait Modalities: A Machine-Learning-Based Approach.

Real-world gait analysis can aid in clinical assessments and influence related interventions, free from the restrictions of a laboratory setting. Using individual accelerometers, we aimed to use a simple machine learning method to quantify the performance of the discrimination between three self-selected cyclical locomotion types using accelerometers placed at frequently referenced attachment locations. Thirty-five participants walked along a 10 m walkway at three different speeds. Triaxial accelerometers were attached to the sacrum, thighs and shanks. Slabs of magnitude, three-second-long accelerometer data were transformed into two-dimensional Fourier spectra. Principal component analysis was undertaken for data reduction and feature selection, followed by discriminant function analysis for classification. Accuracy was quantified by calculating scalar accounting for the distances between the three centroids and the scatter of each category's cloud. The algorithm could successfully discriminate between gait modalities with 91% accuracy at the sacrum, 90% at the shanks and 87% at the thighs. Modalities were discriminated with high accuracy in all three sensor locations, where the most accurate location was the sacrum. Future research will focus on optimising the data processing of information from sensor locations that are advantageous for practical reasons, e.g., shank for prosthetic and orthotic devices.

Quantitative methods used to evaluate balance, postural control, and the fear of falling in lower limb prosthesis users: A systematic review.

Problems with balance, postural control, and fear of falling are highly prevalent in lower limb prosthesis users, with much research conducted to understand these issues. The variety of tools used to assess these concepts presents a challenge when interpreting research outcomes. This systematic review aimed to provide a synthesis of quantifiable methods used in the evaluation of balance, postural control, and fear of falling in lower limb prosthesis users with an amputation level at or proximal to the ankle joint. A systematic search was conducted in CINAHL, Medline, AMED, Cochrane, AgeLine, Scopus, Web of Science, Proquest, PsycINFO, PsycArticles, and PubPsych databases followed by additional manual searching via reference lists in the reviewed articles databases. Included articles used quantitative measure of balance or postural control as one of the dependent variables, lower limb prosthesis users as a sample group, and were published in a peer-reviewed journal in English. Relevant assessment questions were created by the investigators to rate the assessment methods used in the individual studies. Descriptive and summary statistics are used to synthesize the results. The search yielded (n = 187) articles assessing balance or postural control (n = 5487 persons in total) and (n = 66) articles assessing fear of falling or balance confidence (n = 7325 persons in total). The most used test to measure balance was the Berg Balance Scale and the most used test to measure fear of falling was the Activities-specific Balance Confidence scale. A large number of studies did not present if the chosen methods were valid and reliable for the lower limb prosthesis users. Among study limitations, small sample size was common.

Perspectives from research and practice: A survey on external load monitoring and bone in sport.

Introduction: There is limited information regarding the association between external load and estimated bone load in sport, which may be important due to the influence exercise can have on bone accrual and injury risk. The aim of this study was to identify external load measuring tools used by support staff to estimate bone load and assess if these methodologies were supported in research. Methods: A survey was comprised of 19 multiple choice questions and the option to elaborate on if/how they monitor external load and if/how they used them to estimate bone load. A narrative review was performed to assess how external load is associated to bone in research. Results: Participants were required to be working as support staff in applied sport. Support staff (n = 71) were recruited worldwide with the majority (85%) working with professional elite athletes. 92% of support staff monitored external load in their organisation, but only 28% used it to estimate bone load. Discussion: GPS is the most commonly used method to estimate bone load, but there is a lack of research assessing GPS metrics with bone load. Accelerometry and force plates were among the most prevalent methods used to assess external load, but a lack of bone specific measurements were reported by support staff. Further research exploring how external load relates to bone is needed as there is no consensus on which method of external load is best to estimate bone load in an applied setting.

Personalized Offloading Treatments for Healing Plantar Diabetic Foot Ulcers.

BACKGROUND: Non-removable knee-high devices are the gold-standard offloading treatments to heal plantar diabetic foot ulcers (DFUs). These devices are underused in practice for a variety of reasons. Recommending these devices for all patients, regardless of their circumstances and preferences influencing their ability to tolerate the devices, does not seem a fruitful approach. PURPOSE: The aim of this article is to explore the potential implications of a more personalized approach to offloading DFUs and suggest avenues for future research and development. METHODS: Non-removable knee-high devices effectively heal plantar DFUs by reducing plantar pressure and shear at the DFU, reducing weight-bearing activity and enforcing high adherence. We propose that future offloading devices should be developed that aim to optimize these mechanisms according to each individual's needs. We suggest three different approaches may be developed to achieve such personalized offloading treatment. First, we suggest modular devices, where different mechanical features (rocker-bottom sole, knee-high cast walls/struts, etc.) can be added or removed from the device to accommodate different patients' needs and the evolving needs of the patient throughout the treatment period. Second, advanced manufacturing techniques and novel materials could be used to personalize the design of their devices, thereby improving common hindrances to their use, such as devices being heavy, bulky, and hot. Third, sensors could be used to provide real-time feedback to patients and clinicians on plantar pressures, shear, weight-bearing activity, and adherence. CONCLUSIONS: By the use of these approaches, we could provide patients with personalized devices to optimize plantar tissue stress, thereby improving clinical outcomes.

Exploring the perspectives of prosthetic and orthotic users: past and present experiences and insights for the future.

PURPOSE: The aim of this work was to qualitatively explore the personal perspectives of prosthetic and orthotic users, in the context of their past and present experiences and understand their insights for the future. MATERIALS AND METHODS: A narrative exploration study design, employing a phenomenological approach was used. Semi-structured interviews were conducted with three female and two male prosthetic and orthotic users from Australia and the United Kingdom. Interviews were analysed, coded and key themes and sub-themes identified. RESULTS: Three themes were identified. The Maximising Opportunity theme linked sub-themes of recreation and pushing boundaries. The Health Care Network theme included sub-themes of communication, peer support and building a team. The final theme, Changes over time, included sub-themes of disability perception, advice and advancements over time. CONCLUSION: Prosthetic and orthotic users identified that there had been vast changes in disability perception, disability rights, and their role in the health care system, along with the variety of technology and materials available. Key findings were that prosthetic and orthotic users want to be listened to, considered central to the health care team, and had a deep understanding of their own health care needs.Implications for rehabilitationProsthesis and orthosis users want to be listened to and considered central within the health care team.Attending medical and allied health teams must recognise that prosthesis and orthosis users have a fundamental understanding of their own health care needs.Themes, whilst potentially generalisable, are derived from specific individuals and may particularly relate to these individuals.

Calculated functional joint center positions are highly variable in individuals with unilateral transtibial amputation walking with identical prosthetic ankle-foot devices.

BACKGROUND: Biomechanical modeling of the lower limbs, including prosthetic componentry, makes a number of assumptions that influence the data obtained and their subsequent interpretation. Calculated prosthetic ankle functional joint center (FJC) positions vary between devices and have been suggested as a possible method of comparing device function. OBJECTIVES: The study aimed to assess the variability of joint center position estimates, calculated using an FJC methodology, in all three planes. This was assessed in participants with unilateral transtibial amputation using an identical prosthetic ankle-foot device during walking on a flat surface. STUDY DESIGN: Case series. TECHNIQUE: Three-dimensional motion capture recorded the position of markers placed on the shank and ankle-foot device of five individuals with unilateral transtibial amputation, as they completed 10 trials of level walking using the same ankle-foot device. The FJC between the prosthetic foot and shank segments were calculated for each trial. RESULTS: The calculated FJC positions were highly variable across individual participants and within each individual. This variability was observed across all three planes of movement and resulted in calculated joint center positions created beyond the physical boundaries of the prosthetic device. CONCLUSIONS: Biomechanical data are affected by lower limb and prosthetic device modeling assumptions. Definition of a prosthetic "ankle" joint using an FJC method results in highly variable "ankle" joint center positions when applied to a prosthetic ankle-foot device. Their use should be discouraged to avoid misleading interpretations of data.

Exploring the interaction of knee and ankle component use on mobility test performance in people with unilateral transfemoral amputation.

BACKGROUND: Ankle-foot and knee components are important determinants of mobility for individuals with transfemoral amputation. Individually, advanced ankle-foot and knee components have been shown to benefit mobility in this group of people. However, it is not clear what effect a variety of combinations of ankle-foot and knee components have on mobility test performance. OBJECTIVES: To assess whether outcomes from mobility tests in people with unilateral transfemoral amputation are influenced by varying combinations of ankle-foot and knee components. STUDY DESIGNS: Repeated measures. METHODS: Nine adults with unilateral transfemoral amputation completed the two-minute walk test, the timed up-and-go test, the L-test, and a custom locomotion course in four randomized prosthetic conditions. These conditions were each a combination of an ankle-foot component (rigid, nonarticulating [RIG] or hydraulically articulating [HYD]) and a knee component (non-microprocessor-controlled [NMPK] or microprocessor-controlled [MPK]). The test-retest reliability and concurrent validity of the custom locomotion course were also established. RESULTS: The best performance in all mobility tests was associated with the MPK + HYD combination, followed by the MPK + RIG, NMPK + HYD, and NMPK + RIG combinations. This effect was statistically significant for the two-minute walk test (P = 0.01, = 0.36) and on threshold for the L-test (P = 0.05, = 0.36), but not statistically significant for the locomotion course (P = 0.07, = 0.38) or the timed up-and-go test (P = 0.12, = 0.22). Locomotion course performance had good to excellent test-retest reliability and strong concurrent validity. CONCLUSION: Using a combination of a HYD ankle-foot and a MPK knee resulted in the highest performance in mobility tests. This was observed in contrast to combinations of prosthetic components that included a rigid ankle-foot component and/or a NMPK knee component.

Development of a theoretical model for upright postural control in lower limb prosthesis users.

Methods used to assess quiet standing in unilateral prosthesis users often assume validity of an inverted pendulum model despite this being shown as invalid in some instances. The aim of the current study was to evaluate the validity of a proposed unilaterally-constrained pin-controller model in explaining postural control in unilateral prosthesis users. Prosthesis users were contrasted against the theoretical model as were able-bodied controls that stood on a platform which unilaterally constrained movement of the CoP. All participants completed bouts of quiet standing with eyes open, eyes closed and with feedback on inter-limb weight bearing asymmetry. Correlation coefficients were used to infer inverted pendulum behavior in both the anteroposterior and mediolateral directions and were derived from both kinematic (body attached markers) and kinetic (centre of pressure) experimental data. Larger, negative correlation coefficients reflected better model adherence, whilst low or no correlation reflected poorer model adherence. Inverted pendulum behavior derived from kinematic data, indicated coefficients of high magnitude in both mediolateral (all cases range 0.71-0.78) and anteroposterior (0.88-0.91) directions, irrespective of groups. Inverted pendulum behavior derived from kinetic data in the anteroposterior direction indicated validity of the model with large negative coefficients associated with the unconstrained/intact limbs (prosthesis users: - 0.45 to - 0.65, control group: - 0.43 to - 0.72), small coefficients in constrained/prosthetic limbs (prosthesis users: - 0.02 to 0.07, control group: 0.13-0.26) and large negative coefficients in combined conditions (prosthesis users: - 0.36 to - 0.56, control group: - 0.71 to - 0.82). For the mediolateral direction, coefficients were negligible for individual limbs (0.03-0.17) and moderate to large negative correlations, irrespective of group (- 0.31 to - 0.73). Data suggested both prosthesis users' and able-bodied individuals' postural control conforms well to that predicted by a unilaterally-constrained pin-controller model, which has implications for the fundamental control of posture in transtibial prosthesis users.

STEPFORWARD study: a randomised controlled feasibility trial of a self-aligning prosthetic ankle-foot for older patients with vascular-related amputations.

OBJECTIVES: To determine the feasibility of conducting a full-scale randomised controlled trial (RCT) of the effectiveness and cost-effectiveness of a self-aligning prosthetic ankle-foot compared with a standard prosthetic ankle-foot. DESIGN: Multicentre parallel group feasibility RCT. SETTING: Five prosthetics centres in England recruiting from July 2018 to August 2019. PARTICIPANTS: Adults aged ≥50 years with a vascular-related or non-traumatic transtibial amputation for 1 year or longer, categorised as having 'limited community mobility' and using a non-self-aligning ankle-foot. INTERVENTION: Participants were randomised into one of two groups for 12 weeks: self-aligning prosthetic ankle-foot or existing non-self-aligning prosthetic ankle-foot. OUTCOMES: Feasibility measures: recruitment, consent and retention rates; and completeness of questionnaire and clinical assessment datasets across multiple time points. Feasibility of collecting daily activity data with wearable technology and health resource use data with a bespoke questionnaire. RESULTS: Fifty-five participants were randomised (61% of the target 90 participants): n=27 self-aligning ankle-foot group, n=28 non-self-aligning ankle-foot group. Fifty-one participants were included in the final analysis (71% of the target number of participants). The consent rate and retention at final follow-up were 86% and 93%, respectively. The average recruitment rate was 1.25 participants/site/month (95% CI 0.39 to 2.1). Completeness of questionnaires ranged from 89%-94%, and clinical assessments were 92%-95%, including the activity monitor data. The average completion rates for the EQ-5D-5L and bespoke resource use questionnaire were 93% and 63%, respectively. CONCLUSIONS: This feasibility trial recruited and retained participants who were categorised as having 'limited community mobility' following a transtibial amputation. The high retention rate of 93% indicated the trial was acceptable to participants and feasible to deliver as a full-scale RCT. The findings support a future, fully powered evaluation of the effectiveness and cost-effectiveness of a self-aligning prosthetic ankle-foot compared with a standard non-self-aligning version with some adjustments to the trial design and delivery. TRIAL REGISTRATION NUMBER: ISRCTN15043643.

The Calculation, Thresholds and Reporting of Inter-Limb Strength Asymmetry: A Systematic Review.

The prevalence of inter-limb strength differences is well documented in the literature however, there are inconsistencies related to measurement and reporting, and the normative values and effects associated with inter-limb asymmetry. Therefore, the aims of this systematic review were to: 1) assess the appropriateness of existing indices for the calculation of asymmetry, 2) interrogate the evidence basis for literature reported thresholds used to define asymmetry and 3) summarise normative levels of inter-limb strength asymmetry and their effects on injury and performance. To conduct this systematic review, scientific databases (PubMed, Scopus, SPORTDiscus and Web of Science) were searched and a total of 3,594 articles were retrieved and assessed for eligibility and article quality. The robustness of each identified asymmetry index was assessed, and the evidence-basis of the identified asymmetry thresholds was appraised retrospectively using the references provided. Fifty-three articles were included in this review. Only four of the twelve identified indices were unaffected by the limitations associated with selecting a reference limb. Eighteen articles applied a threshold to original research to identify "abnormal" asymmetry, fifteen of which utilised a threshold between 10-15%, yet this threshold was not always supported by appropriate evidence. Asymmetry scores ranged between and within populations from approximate symmetry to asymmetries larger than 15%. When reporting the effects of strength asymmetries, increased injury risk and detriments to performance were often associated with larger asymmetry, however the evidence was inconsistent. Limitations of asymmetry indices should be recognised, particularly those that require selection of a reference limb. Failure to reference the origin of the evidence for an asymmetry threshold reinforces doubt over the use of arbitrary thresholds, such as 10-15%. Therefore, an individual approach to defining asymmetry may be necessary to refine robust calculation methods and to establish appropriate thresholds across various samples and methodologies that enable appropriate conclusions to be drawn.

Self-aligning prosthetic device for older patients with vascular-related amputations: protocol for a randomised feasibility study (the STEPFORWARD study).

INTRODUCTION: The majority of older patients with a transtibial amputation are prescribed a standard (more rigid, not self-aligning) prosthesis. These are mostly suitable for level walking, and cannot adjust to different sloped surfaces. This makes walking more difficult and less energy efficient, possibly leading to longer term disuse. A Cochrane Review concluded that there was insufficient evidence to recommend any individual type of prosthetic ankle-foot mechanism. This trial will establish the feasibility of conducting a large-scale trial to assess the effectiveness and cost-effectiveness of a self-aligning prosthesis for older patients with vascular-related amputations and other health issues compared with a standard prosthesis. METHODS AND ANALYSIS: This feasibility trial is a pragmatic, parallel group, randomised controlled trial (RCT) comparing standard treatment with a more rigid prosthesis versus a self-aligning prosthesis. The target sample size is 90 patients, who are aged 50 years and over, and have a transtibial amputation, where amputation aetiology is mostly vascular-related or non-traumatic. Feasibility will be measured by consent and retention rates, a plausible future sample size over a 24-month recruitment period and completeness of outcome measures. Qualitative interviews will be carried out with trial participants to explore issues around study processes and acceptability of the intervention. Focus groups with staff at prosthetics centres will explore barriers to successful delivery of the trial. Findings from the qualitative work will be integrated with the feasibility trial outcomes in order to inform the design of a full-scale RCT. ETHICS AND DISSEMINATION: Ethical approval was granted by Yorkshire and the Humber-Leeds West Research Ethics Committee on 4 May 2018. The findings will be disseminated via peer-reviewed research publications, articles in relevant newsletters, presentations at relevant conferences and the patient advisory group. TRIAL REGISTRATION NUMBER: ISRCTN15043643.

Does an inverted pendulum model represent the gait of individuals with unilateral transfemoral amputation while walking over level ground?

BACKGROUND:: An inverted pendulum model represents the mechanical function of able-bodied individuals walking accurately, with centre of mass height and forward velocity data plotting as sinusoidal curves, 180° out of phase. OBJECTIVES:: This study investigated whether the inverted pendulum model represented level gait in individuals with a unilateral transfemoral amputation. STUDY DESIGN:: Controlled trial. METHODS:: Kinematic and kinetic data from 10 individuals with unilateral transfemoral amputation and 15 able-bodied participants were recorded during level walking. RESULTS:: During level walking, the inverted pendulum model described able-bodied gait well throughout the gait cycle, with median relative time shifts between centre of mass height and velocity maxima and minima between 1.2% and 1.8% of gait cycle. In the group with unilateral transfemoral amputation, the relative time shift was significantly increased during the prosthetic-limb initial double-limb support phase by 6.3%. CONCLUSION:: The gait of individuals with unilateral transfemoral amputation shows deviation from a synchronous inverted pendulum model during prosthetic-limb stance. The reported divergence may help explain such individuals' increased metabolic cost of gait. Temporal divergence of inverted pendulum behaviour could potentially be utilised as a tool to assess the efficacy of prosthetic device prescription. CLINICAL RELEVANCE: The size of the relative time shifts between centre of mass height and velocity maxima and minima could potentially be used as a tool to quantify the efficacy of innovative prosthetic device design features aimed at reducing the metabolic cost of walking and improving gait efficiency in individuals with amputation.

Clinical assessment of depth sensor based pose estimation algorithms for technology supervised rehabilitation applications.

Encouraging rehabilitation by the use of technology in the home can be a cost-effective strategy, particularly if consumer-level equipment can be used. We present a clinical qualitative and quantitative analysis of the pose estimation algorithms of a typical consumer unit (Xbox One Kinect), to assess its suitability for technology supervised rehabilitation and guide development of future pose estimation algorithms for rehabilitation applications. We focused the analysis on upper-body stroke rehabilitation as a challenging use case. We found that the algorithms require improved joint tracking, especially for the shoulder, elbow and wrist joints, and exploiting temporal information for tracking when there is full or partial occlusion in the depth data.

Do Predictive Relationships Exist Between Postural Control and Falls Efficacy in Unilateral Transtibial Prosthesis Users?

OBJECTIVE: To assess whether variables from a postural control test relate to and predict falls efficacy in prosthesis users. DESIGN: Twelve-month within- and between-participants repeated measures design. Participants performed the limits of stability (LOS) test protocol at study baseline and at 6-month follow-up. Participants also completed the Falls Efficacy Scale-International (FES-I) questionnaire, reflecting the fear of falling, and reported the number of falls monthly between study baseline and 6-month follow-up, and additionally at 9- and 12-month follow-ups. SETTING: University biomechanics laboratories. PARTICIPANTS: Participants (N=24) included a group of active unilateral transtibial prosthesis users of primarily traumatic etiology (n=12) with at least 1 year of prosthetic experience and age- and sex-matched control participants (n=12). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Postural control variables derived from center of pressure data obtained during the LOS test, which was performed on and reported by the Neurocom Pro Balance Master, namely reaction time, movement velocity (MVL), endpoint excursion (EPE), maximum excursion (MXE), and directional control (DCL). Number of falls and total FES-I scores. RESULTS: During the study period, the prosthesis users group had higher FES-I scores (U=33.5, P=.02), but experienced a similar number of falls, compared to the control group. Increased FES-I scores were associated with decreased EPE (r= -0.73, P=.02), MXE (r= -0.83, P<.01) and MVL (r= -0.7, P=.03) in the prosthesis users group, and DCL (r= -0.82, P<.01) in the control group, all in the backward direction. CONCLUSIONS: Study baseline measures of postural control, in the backward direction only, are related to and potentially predictive of subsequent 6-month FES-I scores in relatively mobile and experienced prosthesis users.

Development of a limits of stability protocol for use in transtibial prosthesis users: Learning effects and reliability of outcome variables.

The aims of this study were to empirically quantify reliability and learning effects of a Limits of Stability protocol for transtibial prosthesis users. Outcome variables from center of pressure and center of mass were tested on: 1) multiple test repetitions within a single test occasion; and 2) between multiple test occasions. Trantibial prosthesis users (n=7) and matched controls (n=7) executed five trials of the Limits of Stability protocol on two occasions per day, on two consecutive days. Inter-trial learning effects and reliability of outcomes extracted via center of mass and center of pressure were evaluated utilizing standard biomechanics laboratory equipment. Reliability was good to excellent except the reaction time variable which was poor (Pooled 95%CI of ICC=0.248-0.484). An inter-trial learning effect was present in directional control for prosthesis users when the first trial was included in analysis (center of mass: 95%CI of r=0.065-0.239; center of pressure: 95%CI of r=0.076-0.249). The use of standard biomechanics lab equipment can produce reliable results for the Limits of Stability protocol. Researchers should be aware of low reliability of reaction time variable in the protocol assessed and should execute at least one practice trial prior to that which is used in subsequent analysis.

Optimisation of a machine learning algorithm in human locomotion using principal component and discriminant function analyses.

Assessment methods in human locomotion often involve the description of normalised graphical profiles and/or the extraction of discrete variables. Whilst useful, these approaches may not represent the full complexity of gait data. Multivariate statistical methods, such as Principal Component Analysis (PCA) and Discriminant Function Analysis (DFA), have been adopted since they have the potential to overcome these data handling issues. The aim of the current study was to develop and optimise a specific machine learning algorithm for processing human locomotion data. Twenty participants ran at a self-selected speed across a 15m runway in barefoot and shod conditions. Ground reaction forces (BW) and kinematics were measured at 1000 Hz and 100 Hz, respectively from which joint angles (°), joint moments (N.m.kg-1) and joint powers (W.kg-1) for the hip, knee and ankle joints were calculated in all three anatomical planes. Using PCA and DFA, power spectra of the kinematic and kinetic variables were used as a training database for the development of a machine learning algorithm. All possible combinations of 10 out of 20 participants were explored to find the iteration of individuals that would optimise the machine learning algorithm. The results showed that the algorithm was able to successfully predict whether a participant ran shod or barefoot in 93.5% of cases. To the authors' knowledge, this is the first study to optimise the development of a machine learning algorithm.

ß-alanine supplementation improves in-vivo fresh and fatigued skeletal muscle relaxation speed.

PURPOSE: In fresh muscle, supplementation with the rate-limiting precursor of carnosine, ß-alanine (BA), results in a decline in muscle half-relaxation time (HRT) potentially via alterations to calcium (Ca2+) handling. Accumulation of hydrogen cation (H+) has been shown to impact Ca2+ signalling during muscular contraction, carnosine has the potential to serve as a cytoplasmic regulator of Ca2+ and H+ coupling, since it binds to both ions. The present study examined the effect of BA supplementation on intrinsic in-vivo isometric knee extensor force production and muscle contractility in both fresh and fatigued human skeletal muscle assessed during voluntary and electrically evoked (nerve and superficial muscle stimulation) contractions. METHODS: Twenty-three males completed two experimental sessions, pre- and post- 28 day supplementation with 6.4 g.day-1 of BA (n = 12) or placebo (PLA; n = 11). Isometric force was recorded during a series of voluntary and electrically evoked knee extensor contractions. RESULTS: BA supplementation had no effect on voluntary or electrically evoked isometric force production, or twitch electromechanical delay and time-to-peak tension. There was a significant decline in muscle HRT in fresh and fatigued muscle conditions during both resting (3 ± 13%; 19 ± 26%) and potentiated (1 ± 15%; 2 ± 20%) twitch contractions. CONCLUSIONS: The mechanism for reduced HRT in fresh and fatigued skeletal muscle following BA supplementation is unclear. Due to the importance of muscle relaxation on total energy consumption, especially during short, repeated contractions, BA supplementation may prove to be beneficial in minimising contractile slowing induced by fatigue. TRIAL REGISTRATION: The trial is registered with Clinicaltrials.gov, ID number NCT02819505.