Now showing 1 - 10 of 10
  • Publication
    A method for monitoring reactive strength index
    Ubiquitous motion sensors in shoes and clothing are becoming more prevalent. This new data stream opens a large opportunity to gain a deeper understanding of human movement. This paper describes the development and validation of an algorithm to calculate reactive strength index (RSI) from an accelerometer mounted at the ankle. Compared to the gold standard force-plate, the accelerometer and algorithm RSI had r = 0.98, mean difference = 0.001 m/sec and a confidence interval ranging from 0.12 to -0.11 m/sec. Difficulty in accurately identifying take-off using the accelerometer was the main source of measurement error.
    Scopus© Citations 9  2597
  • Publication
    Validation and comparison of shank and lumbar-worn IMUs for step time estimation
    Gait assessment is frequently used as an outcome measure to determine changes in an individual's mobility and disease processes. Inertial measurement units (IMUs) are quickly becoming commonplace in gait analysis. The purpose of this study was to determine and compare the validity of shank and lumbar IMU mounting locations in the estimation of temporal gait features. Thirty-seven adults performed 20 walking trials each over a gold standard force platform while wearing shank and lumbar-mounted IMUs. Data from the IMUs were used to estimate step times using previously published algorithms and were compared with those derived from the force platform. There was an excellent level of correlation between the force platform and shank (r=0.95) and lumbar-mounted (r=0.99) IMUs. Bland-Altman analysis demonstrated high levels of agreement between the IMU and the force platform step times. Confidence interval widths were 0.0782 s for the shank and 0.0367 s for the lumbar. Both IMU mounting locations provided accurate step time estimations, with the lumbar demonstrating a marginally superior level of agreement with the force platform. This validation indicates that the IMU system is capable of providing step time estimates within 2% of the gold standard force platform measurement.
      524Scopus© Citations 3
  • Publication
    Validation of temporal gait metrics from three IMU locations to the gold standard force plate
    The purpose of this work is to compare temporal gait parameters from three different IMU locations to the gold standard force platform. 33 subjects (12 F, 21 M) performed twenty gait trials each while wearing inertial measurement units (IMUs) on the trunk, both shanks and both feet. Data was simultaneously collected from a laboratory embedded force plate. Step times were derived from the raw IMU data at the three IMU locations using methods that have been shown to be accurate. Step times from all locations were valid compared to the force plate. Foot IMU step time was the most accurate (Pearson = .991, CI width = 3.00e2), the trunk IMU was the next most accurate (Pearson = .974, CI width = 4.85e2) and shank step time was the least accurate (Pearson = .958, CI width = 6.80e2). All three sensing locations result in valid estimations of step time compared to the gold standard force plate. These results suggest that the foot location would be most appropriate for clinical applications where very precise temporal parameter detection is required.
      812Scopus© Citations 12
  • Publication
    Quantifying show jumping horse rider expertise using IMUs
    Horse rider ability has long been measured using horse performance, competition results and visual observation. Scientific methods of measuring rider ability on the flat are emerging such as measuring position angles and harmony of the horse-rider system. To date no research has quantified rider ability in show jumping. Kinematic analysis and motion sensors have been used in sports other than show jumping to measure the quality of motor control patterns in humans. The aim of this study was to quantify rider ability in show jumping using body-mounted IMUs. Preliminary results indicate that there are clear differences in experienced and novice riders during show jumping.
      1929Scopus© Citations 17
  • Publication
    Lower Limb Interjoint Postural Coordination One Year after First-Time Lateral Ankle Sprain
    Introduction: Longitudinal analyses of participants with a history of lateral ankle sprain are lacking. This investigation combined measures of lower limb interjoint coordination and stabilometry to evaluate static unipedal stance with the eyes open (condition 1) and closed (condition 2) in a group of participants with chronic ankle instability (CAI) compared to lateral ankle sprain ‘‘copers’’ (both recruited 12 months after sustaining an acute first-time lateral ankle sprain) and a group of noninjured controls. Methods: Twenty-eight participants with CAI, 42 lateral ankle sprain ‘‘copers,’’ and 20 noninjured controls completed three 20-s singlelimb stance trials in conditions 1 and 2. An adjusted coefficient of multiple determination statistic was used to compare stance limb threedimensional kinematic data for similarity to establish patterns of interjoint coordination. The fractal dimension of the stance limb center of pressure path was also calculated. Results: Between-group analyses revealed that participants with CAI displayed notable increases in ankle–hip linked coordination compared with both lateral ankle sprain ‘‘copers’’ (j0.52 (1.05) vs 0.28 (0.9), P = 0.007) and controls (j0.52 (1.05) vs 0.63 (0.64), P = 0.006) in condition 1 and compared with controls only (0.62 (1.92) vs 0.1 (1.0) P = 0.002) in condition 2. Participants with CAI also exhibited a decrease in the fractal dimension of the center-of-pressure path during condition 2 compared with both controls and lateral ankle sprain ‘‘copers.’’ Conclusions: Participants with CAI present with a hip-dominant strategy of eyes-open and eyes-closed static unipedal stance. This coincided with reduced complexity of the stance limb center of pressure path in the eyes-closed condition.
      469Scopus© Citations 20
  • Publication
    Acceleration and rotation rate profile comparison from inertial sensors mounted on the service arm between tennis players of different skill level
    Biomechanical performance is an important factor for developing tennis players. The tennis serve happens so quickly that it can be difficult for even the trained eye of an experienced coach to identify the miniscule movement differences that can make the difference between being a successful player and not. Traditionally, biomechanical information is captured with an optical-marker system, which is expensive and requires a specialized team to operate (Tanabe & Ito, 2007). Advances in wearable sensor technology means that it might one day be possible to measure kinematics from sensors embedded in athletic clothing. Currently, there are inertial sensors which can be used in training, but are too cumbersome for an athlete to wear in a game situation. The initial step is to use these sensors to determine what type of information it is possible to get from inertial sensors on the athlete, which is the purpose of this study.
  • Publication
    Using a foot mounted accelerometer to detect changes in gait patterns
    The purpose of this study is to investigate how datafrom a foot mounted accelerometer can be used to detect motorpattern healthy subjects performed walking trails under twodifferent conditions; normal and stiff ankle walking. Lowerbody kinematic data were collected as well as accelerometerdata from both feet. An algorithm is presented which quantifiesrelevant swing phase characteristics from the footaccelerometer. Peak total acceleration during initial swing wassignificantly higher in the stiff ankle condition (M = 33.10, SD =5.12) than in the normal walking condition (M = 29.47, SD =5.75; t(7) = 4.32, p = .003, two-tailed). There was a large effectsize (eta squared = 0.853). Time between peak accelerationduring initial swing to foot strike was significantly shorter inthe stiff ankle condition (M = 0.42, SD = 0.02) than in thenormal condition (M = 0.44, SD = 0.03; t(7) = -2.54, p = .039,two- tailed). There was a large effect size (eta squared = 0.693).Simple to process metrics from tri-axial accelerometer data onthe foot show potential to detect changes in ankle kinematicpatterns.
      654Scopus© Citations 10
  • Publication
    Coordination and symmetry patterns during the drop vertical jump, 6-months after first-time lateral ankle sprain
    To evaluate the adaptive movement and motor control patterns of a group with a 6-month history of first-time lateral ankle sprain (LAS) injury during a drop vertical jump (DVJ) task. Fifty-one participants with a 6-month history of first-time acute LAS injury and twenty controls performed a DVJ task. 3D kinematic and sagittal plane kinetic profiles were plotted for the lower extremity joints of both limbs for the drop jump (phase 1) and drop landing (phase 2) phases of the DVJ. Inter-limb symmetry and the rate of impact modulation (RIM) relative to bodyweight (BW) during both phases of the DVJ were also determined. LAS participants displayed bilateral increases in knee flexion and an increase in ankle inversion during phases 1 and 2, respectively. They also displayed reduced ankle plantar flexion on their injured limb during both phases of the DVJ (p < 0.05); increased inter-limb asymmetry of RIM was noted for both phases of the DVJ, while the moment-of-force profile exhibited bilaterally greater hip extensor dominance during phase 1. Participants with a 6-month history of first-time LAS display some movement patterns consistent with those observed in chronic ankle instability populations during similar tasks.
      516Scopus© Citations 23
  • Publication
    Does external walking environment affect gait patterns?
    The objective of this work is to develop an understanding of the relationship between mobility metrics obtained outside of the clinic or laboratory and the context of the external environment. Ten subjects walked with an inertial sensor on each shank and a wearable camera around their neck. They were taken on a thirty minute walk in which they mobilized over the following conditions; normal path, busy hallway, rough ground, blind folded and on a hill. Stride time, stride time variability, stance time and peak shank rotation rate during swing were calculated using previously published algorithms. Stride time was significantly different between several of the conditions. Technological advances mean that gait variables can now be captured as patients go about their daily lives. The results of this study show that the external environment has a significant impact on the quality of gait metrics. Thus, context of external walking environment is an important consideration when analyzing ambulatory gait metrics from the unsupervised home and community setting.
      443Scopus© Citations 17
  • Publication
    An Ambulatory Method of Identifying Anterior Cruciate Ligament Reconstructed Gait Patterns
    The use of inertial sensors to characterize pathological gait has traditionally been based on the calculation of temporal and spatial gait variables from inertial sensor data. This approach has proved successful in the identification of gait deviations in populations where substantial differences from normal gait patterns exist; such as in Parkinsonian gait. However, it is not currently clear if this approach could identify more subtle gait deviations, such as those associated with musculoskeletal injury. This study investigates whether additional analysis of inertial sensor data, based on quantification of gyroscope features of interest, would provide further discriminant capability in this regard. The tested cohort consisted of a group of anterior cruciate ligament reconstructed (ACL-R) females and a group of non-injured female controls, each performed ten walking trials. Gait performance was measured simultaneously using inertial sensors and an optoelectronic marker based system. The ACL-R group displayed kinematic and kinetic deviations from the control group, but no temporal or spatial deviations. This study demonstrates that quantification of gyroscope features can successfully identify changes associated with ACL-R gait, which was not possible using spatial or temporal variables. This finding may also have a role in other clinical applications where small gait deviations exist.
      400Scopus© Citations 40