Brendan Burkett

The use of a single inertial sensor to identify stride, step, and stance durations of running gait.

Current developments in inertial sensor technology could enable the measurement of running gait outside of the traditional laboratory environment. The purpose of this research was to determine the level of agreement between an inertial sensor and infrared camera based estimates of stride, step, and stance durations across a range of running speeds. An inertial sensor was placed on the sacrum of 10 elite national standard runners, and the stride, step, and stance of running gait were compared. A total of 504 samples were collected and the running velocities stratified into three equal groups of low (10-12 km/h), medium (13-15 km/h), and high (16-19 km/h). A single inertial sensor was found to be suitable for identifying stride duration with Bland-Altman limits of agreement of 95%. The stride data showed agreement at less than 0.02s for most limits. Agreement for step showed five of the eight upper and lower limits below 0.02s. The largest differences between both capture methods were for stance. An average bias of 0.0008s was found and standard error ranged between 0.0004s and 0.0009s across all variables. The results from this research found that inertial sensors are suitable to measure stride, step, and stance duration, and provide the opportunity to measure running gait outside of the traditional laboratory.

Technology in Paralympic sport: performance enhancement or essential for performance?

Background People with disabilities often depend on assistive devices to enable activities of daily living as well as to compete in sport. Technological developments in sport can be controversial. Objectives To review, identify and describe current technological developments in assistive devices used in the summer Paralympic Games; and to prepare for the London 2012 Games, the future challenges and the role of technology are debated. Methods A systematic review of the peer-reviewed literature and personal observations of technological developments at the Athens (2004) and Beijing (2008) Paralympic Games was conducted. Results Standard assistive devices can inhibit the Paralympians’ abilities to perform the strenuous activities of their sports. Although many Paralympic sports only require technology similar to their Olympic counterparts, several unique technological modifications have been made in prosthetic and wheelchair devices. Technology is essential for the Paralympic athlete, and the potential technological advantage for a Paralympian, when competing against an Olympian, is unclear. Conclusion Technology must match the individual requirements of the athlete with the sport in order for Paralympians to safely maximise their performance. Within the ‘performance enhancement or essential for performance?’ debate, any potential increase in mechanical performance from an assistive device must be considered holistically with the compensatory consequences the disability creates. To avoid potential technology controversies at the 2012 London Olympic and Paralympic Games, the role of technology in sport must be clarified.

Walking and running inter-limb asymmetry for Paralympic trans-femoral amputees, a biomechanical analysis:

The aim of this project was to further the research and understanding of the trans-femoral amputees ability to walk and run by comparing the changes in walking and running inter-limb asymmetry. An objective biomechanical analysis was conducted on four male trans-femoral amputees, all members of the Australian Paralympic training squad for the 1996 Atlanta Paralympic Games. The data was collected in the biomechanics laboratories at Queensland University of Technology and the Australian Institute of Sport. The main outcomes measure a synchronised 3D kinematic (200Hz), kinetic (600Hz) and temporal analysis of walking at self-selected (1.1-1.3m/s), and at maximal running speed (2.5-4.3m/s). The walking and running biomechanical data was summarised into 27 indices of symmetry. The results showed that for all subjects the inter-limb asymmetry was significantly different at running speed, when compared to the walking speed. Using indices of symmetry 79% of the kinematic, 67% of the kinetic, and 67% of the temporal measurements identified better inter-limb asymmetry when the subjects walked, compared to running. This study objectively identified that when Paralympic level amputees ran on their standard running prosthesis, the inter-limb asymmetry was exacerbated.

Shifting boundaries in sports technology and disability: equal rights or unfair advantage in the case of Oscar Pistorius?

In Paralympic sports, athletes often depend on some form of equipment to enable activities of daily living, including the ability to participate in sport. Determining precisely when technology assists sports performance and when it transforms or distorts them presents a philosophical and ethical dilemma. We raise the conceptual problem of line-drawing between promoting rights of access to equipment that provide equal opportunity while proscribing ‘boosting’ technology where athletes with a disability are afforded an unfair advantage. We set out a multidisciplinary analysis regarding the Olympic eligibility for Oscar Pistorius, the double-amputee world record holder, who runs with transtibial prostheses. We present scientific data comparing the prosthesis with an anatomical limb, and then contextualise the issue of shifting the boundaries of sports technology and disability to inform better policy-making in relation to the athlete–technology eligibility debate.

Lower Limb Functional Index: Development and Clinimetric Properties

Background Existing lower-limb, region-specific, patient-reported outcome measures have clinimetric limitations, including limitations in psychometric characteristics (eg, lack of internal consistency, lack of responsiveness, measurement error) and the lack of reported practical and general characteristics. A new patient-reported outcome measure, the Lower Limb Functional Index (LLFI), was developed to address these limitations. Objective The purpose of this study was to overcome recognized deficiencies in existing lower-limb, region-specific, patient-reported outcome measures through: (1) development of a new lower-extremity outcome scale (ie, the LLFI) and (2) evaluation of the clinimetric properties of the LLFI using the Lower Extremity Functional Scale (LEFS) as a criterion measure. Design This was a prospective observational study. Methods The LLFI was developed in a 3-stage process of: (1) item generation, (2) item reduction with an expert panel, and (3) pilot field testing (n=18) for reliability, responsiveness, and sample size requirements for a larger study. The main study used a convenience sample (n=127) from 10 physical therapy clinics. Participants completed the LLFI and LEFS every 2 weeks for 6 weeks and then every 4 weeks until discharge. Data were used to assess the psychometric, practical, and general characteristics of the LLFI and the LEFS. The characteristics also were evaluated for overall performance using the Measurement of Outcome Measures and Bot clinimetric assessment scales. Results The LLFI and LEFS demonstrated a single-factor structure, comparable reliability (intraclass correlation coefficient [2,1]=.97), scale width, and high criterion validity (Pearson r=.88, with 95% confidence interval [CI]). Clinimetric performance was higher for the LLFI compared with the LEFS on the Measurement of Outcome Measures scale (96% and 95%, respectively) and the Bot scale (100% and 83%, respectively). The LLFI, compared with the LEFS, had improved responsiveness (standardized response mean=1.75 and 1.64, respectively), minimal detectable change with 90% CI (6.6% and 8.1%, respectively), and internal consistency (α=.91 and .95, respectively), as well as readability with reduced user error and completion and scoring times. Limitations Limitations of the study were that only participants recruited from outpatient physical therapy clinics were included and that no specific conditions or diagnostic subgroups were investigated. Conclusion The LLFI demonstrated sound clinimetric properties. There was lower response error, efficient completion and scoring, and improved responsiveness and overall performance compared with the LEFS. The LLFI is suitable for assessment of lower-limb function.

Modification of the Upper Limb Functional Index to a Three-point Response Improves Clinimetric Properties

STUDY DESIGN Observational two-stage. INTRODUCTION To achieve optimal clinimetric properties for outcome measures, both practical and psychometric, ongoing improvements are required. PURPOSE OF THE STUDY To evaluate if the Upper Limb Functional Index (ULFI) clinimetric properties are improved by modification to a three-point response option and to verify the factor structure. METHODS Stage 1, calibration (n=139) used ULFI dichotomous responses, and stage 2, validation (n=117) used a three-point response option. The clinimetric properties were compared in physical therapy outpatients with the QuickDASH as the reference standard. Repeated measurements were made at two to four weekly intervals. RESULTS The ULFI three-point response option improved reliability [intraclass correlation coefficient (2,1)=0.98], internal consistency (alpha=0.92), QuickDASH concurrent validity (r=0.86), and responsiveness. Minimal detectable change (90% confidence interval) was 7.9%, and factor structure was unidimensional. Missing responses were <0.5%, and practical characteristics were unchanged. CONCLUSIONS The enhanced reliability and reduced errors with unchanged practicality demonstrate the ULFI improvements through modification to a three-point response option. LEVEL OF EVIDENCE 2c.

An integrated swimming monitoring system for the biomechanical analysis of swimming strokes

This paper describes the development of a complete wearable swimming system for performance analysis, together with a sample application. The system comprises wearable nodes, data processing tools in MATLAB™ and integration with video. The swimming nodes are small in size and designed to be worn on body segments of interest, typically lower leg, lower arm, and the sacral or cervical regions. Each node contains inertial sensors, screen, data storage and RF communications for synchronisation and data download. The device is controlled using a microcontroller with a scheduler-based operating system to conserve power and is custom-packaged with a user interface and USB port that is fully waterproof. The cost of manufacture is a few hundred dollars in small-run quantities. The developed analysis software builds upon previously developed tools, can communicate with the nodes individually and can synchronise the recording of multiple units through a custom-developed protocol. Video is integrated into the developed tools as a method of presenting the sensor data alongside a more traditional analysis tool. A case study of the system analyses swim stroke phase with video and demonstrates the utility of the system as a tool for temporal stroke phase identification in the high-performance environment.

The force–time profile of elite front crawl swimmers

Abstract In this study, we used recently developed technology to determine the force–time profile of elite swimmers, which enabled coaches to make informed decisions on technique modifications. Eight elite male swimmers with a FINA (Federation Internationale de Natation) rank of 900+ completed five passive (streamline tow) and five net force (arms and leg swimming) trials. Three 50-Hz cameras were used to video each trial and were synchronized to the kinetic data output from a force-platform, upon which a motorized towing device was mounted. Passive and net force trials were completed at the participants maximal front crawl swimming velocity. For the constant tow velocity, the net force profile was presented as a force–time graph, and the limitation of a constant velocity assumption was acknowledged. This allowed minimum and maximum net forces and arm symmetry to be identified. At a mean velocity of 1.92 ± 0.06 m · s−1, the mean passive drag for the swimmers was 80.3 ± 4.0 N, and the mean net force was 262.4 ± 33.4 N. The mean location in the stroke cycle for minimum and maximum net force production was at 45% (insweep phase) and 75% (upsweep phase) of the stroke, respectively. This force–time profile also identified any stroke asymmetry.

Identifying symmetry in running gait using a single inertial sensor

Running gait has been shown to alter due to changes in intensity. It was hypothesised that a sacral mounted single inertial sensor could identify the centre of mass (COM) vertical accelerations. This study aimed to validate this new technique against a criterion measure and to determine the influence of changes in running intensity on COM vertical acceleration and the symmetry of COM vertical acceleration between left and right steps. Ten athletes ran for 5min at their self-selected pace, plus 1km/h above and below this velocity. Validity of the single inertial sensor was determined by comparing COM vertical acceleration against that measured with a six-camera infrared system. Large correlation (r=0.96), a small typical error of estimate (1.84), and mean bias (0.02) were found between the two systems. The greatest magnitude in COM vertical acceleration occurred at the slowest running pace and decreased as pace increased. Sixty percent of the athletes exhibited asymmetry during at least one running pace; 30% were asymmetrical across all three velocities. While significant changes in COM vertical acceleration occurred between the different running velocities, this did not always result in a change in symmetry. This study found that a single inertial sensor can be used as a valid means of measuring COM vertical acceleration. This technique can detect changes in the COM vertical acceleration that may change with running velocity. Gait symmetry (using COM vertical acceleration) during running was also quantified using the inertial sensor.

Validity and reliability of kick count and rate in freestyle using inertial sensor technology

Abstract In freestyle swimming the arm action is routinely quantified by stroke count and rate, yet no method is currently available for quantifying kick. In this study, we assessed the validity and reliability of inertial sensor technology (gyroscope) to assess kick count and rate. Twelve Paralympic swimmers completed a 100-m freestyle-swimming time-trial and freestyle kicking-only time-trial three times each in a season. An algorithm was developed to detect the up and down beat of individual kicks from the gyroscope trace. For comparative purposes, underwater video analysis provided the criterion measure. The standard error of the estimate (validity) for kick count, expressed as a coefficient of variation, was 5.9% (90% confidence interval 5.5 to 6.4) for swimming, and 0.6% (0.5 to 0.6) for kicking-only trials. The mean bias for kick count was −1.7% (−2.4 to −1.1) for swimming, and −0.1% (−0.2 to −0.1) for kicking-only trials. Correlations between the sensor and video for kick count were 0.96 (0.95 to 0.97) for swimming, and 1.00 (1.00 to 1.00) for kicking-only trials. The typical error of the measurement (reliability) between trials was approximately 4% for kick count and rate. The inertial sensors and associated software used generated sufficient validity and reliability estimates to quantify moderate to large changes in kick count and rate in freestyle swimming.