Magnitude Of Linear Acceleration Research Articles

In Deep Water: A Case Study on Kinematics in Deep Water Running

Introduction: This field-based case study assessed linear accelerations of the torso centre of mass (CoM) and the tibia using two wearable sensors in a triathlete performing 20 minutes of continuous deep water running. Methods: One triathlete (36 years; height; 151 cm; weight; 63 kg) participated in this field-based case study. One wearable sensor (an accelerometer) was located on the lumbar five/sacrum one (L5/S1) spinous process as a proxy for the centre of mass (CoM) and on the midpoint of the right tibia to capture linear acceleration magnitudes. The participant then performed 20 minutes of deep water running that was completed at a self-selected pace. Results: No significant differences (p<0.05) in torso CoM and tibia acceleration magnitudes were detected in 20 minutes of deep water running. Despite this, the magnitude of torso CoM and tibia acceleration, notably in the anteroposterior and vertical directions, increased at the midpoint of the deep water run, possibly indicating the onset of fatigue. Conclusions: This field-based case study suggests that a wearable sensor can reliably detect variations to the torso CoM and tibia by way of linear acceleration magnitudes in 20 minutes of continuous deep water running. Based on these results, it is possible that the increased acceleration observed at the tibia were due to the onset of fatigue. Future investigations with a larger number of participants are needed to further explore the relationship between torso and tibia acceleration and fatigue in deep water running.

A Case Study in Upper Body Kinematics of an Elite Axe Thrower Using Sensor Technology

Introduction: This field-based case study assessed linear accelerations of the scapula and elbow in an elite axe thrower in three different axe throwing techniques using two wearable sensors. Methods: One elite axe thrower (35 years; height 181 cm; weight 92 kg) participated in this case study. One wearable sensor (an accelerometer) was located on the dorsal surface of the upper thorax between the medial borders of the scapula. An additional sensor was located on the medial epicondyle of the right elbow to capture linear acceleration magnitudes. The participant performed three different throwing techniques, namely a one hand underarm throw, a two-handed overhead throw, and a one hand overarm throw for a total of four repetitions. Results: Significant differences in scapula acceleration magnitudes were detected in the three throwing techniques analyzed along with significant differences in all acceleration channels (p < 0.001). In contrast, no significant differences in triaxial acceleration magnitude were observed in the elbow in all throwing techniques (p > 0.50). Conclusions: Magnitudes of scapular acceleration varied significantly depending on the type of throw. In contrast, acceleration magnitudes at the elbow displayed high variability despite a non-significant outcome. A wearable sensor could be a valuable tool to enhance throwing performance.

Pilot Collection and Evaluation of Head Kinematics in Stock Car Racing.

The goal of this work was to collect on-track driver head kinematics using instrumented mouthpieces and characterize environmental exposure to accelerations and vibrations. Six NASCAR drivers were instrumented with custom-fit mouthpieces to collect head kinematic data. Devices were deployed at four tracks during practice and testing environments and configured to collect approximately 11 min of linear acceleration and rotational velocity data at 200 Hz. This continuous data collection, combined with film review, allowed extraction of complete laps of data. In addition to typical data processing methods, a moving-point average was calculated and subtracted from the overall signal for both linear acceleration and rotational velocity to determine the environmental component of head motion. The current analysis focuses on 42 full laps of data collected at four data collection events. The number of laps per track ranged from 2 to 23. Linear acceleration magnitudes for all 42 laps ranged from 2.46 to 7.48 g and rotational velocity ranged from 1.25 to 3.35 rad/s. After subtracting the moving average, linear acceleration ranged from 0.92 to 5.45 g and rotational velocity ranged from 0.57 to 2.05 rad/s. This study has established the feasibility of using an instrumented mouthpiece to measure head kinematics in NASCAR and presented a technique for isolating head motion due to cornering acceleration from those due to short-term perturbations experienced by the driver.

Wearable inertial sensors for gait analysis in adults with osteoarthritis – a scoping review

Purpose: While there is no cure for OA, lower limb biomechanical data collected during walking can provide valuable information on the etiology, progression, and treatment of this disease. Unfortunately, these conventional systems can be expensive and time-consuming, which make them inaccessible to many clinicians. Fortunately, the advent of wearable inertial sensors has provided an accessible and affordable alternative to conventional optical gait analysis systems. This growing area of research has demonstrated the immense potential of these devices, but the literature remains fragmented across the broad field of OA biomechanics. Therefore, in conducting this scoping review we aimed to summarize the growing body of literature using wearable inertial sensors for gait analysis in OA. Specifically, our objective was to identify biomechanical outcomes and applications of wearable inertial sensors for assessing walking gait in adults diagnosed with lower limb OA. We aimed to highlight the quality and types of research prominent in this field, with a focus on biomechanical outcomes and important gaps to be addressed in future research. Methods: We searched six databases using predetermined search terms which highlighted the broad areas of inertial sensors, gait, and osteoarthritis on June 9, 2020. Specifically, our criteria aimed to include studies which used inertial sensors (i.e., accelerometers, gyroscopes, and/or magnetometers) for walking gait analysis in adults diagnosed with lower limb OA (e.g., hip, knee, or ankle). Studies which only examined outcomes not related to an assessment of walking gait patterns (e.g., daily step count, physical activity, energy expenditure) were not considered. Two authors independently conducted title and abstract reviews, followed by full-text screening. Study quality was also assessed by two independent reviewers. Data were extracted from included studies in areas such as study design, osteoarthritis sample, protocols, and inertial sensor outcomes. Results: Search and Screening Results. Our search strategy identified a total of 561 articles and 376 articles after duplicate removal. A total of 107 articles were passed to full-text screening which were further reduced to 72 studies included in our scoping review. The PRISMA flow diagram presented in Figure 1 documents all exclusions at the full-text level. The most common reason for exclusion at the full-text level was “no biomechanical outcomes”, which was generally the result of studies measuring only physical activity or step count data. Osteoarthritis Sample and Protocols. The gait of 2,159 adults with OA were examined using wearable inertial sensors across the 72 studies. The most common location of OA studied was the knee (n=46), followed by the hip (n=22), and the ankle (n=7). The most common placement of sensors was the back/pelvis/torso (n=41), followed closely by the shank (n=40), foot (n=31), thigh (n=27), and head/neck (n=5). The most common study design was found to be cross-sectional (n=44), with most examining differences in gait between OA and controls (n=34). There were 21 studies that utilized some type of longitudinal design, with most examining the effect of surgery (n=17) and 4 examining other interventions (e.g., exercise, gait retraining). Figure 2 illustrates the number of included studies published each year, grouped by study design. Inertial Sensor Outcomes. Mean ST parameters were the most common outcome as they were presented in 45 studies. The variability and symmetry of ST parameters were each presented in 14 studies. The second most common outcome was segment orientation or joint angles, measured in 33 studies. Linear acceleration magnitudes were the third most common and appeared in 22 studies, with estimates of variability or symmetry components surrounding these outcomes present in 10 studies. Figure 3 provides a visual representation of gait outcomes by sensor locations. Conclusions: Wearable inertial sensors provide an accessible and affordable tool to support our understanding and treatment of OA through gait analyses. We identified 72 studies which have utilized wearable inertial sensors to assess OA gait. Overall, these studies measured a wide range of outcomes from mean ST parameters to the KAM and more. Similarly, the patient populations, study designs, and sensor protocols varied greatly between studies. Two-thirds of these studies were published in the past five years (Figure 1) and we predict that 2019 may be an inflection point whereafter remarkable growth will occur in this area for years to come. While mean ST parameters remain the most assessed outcomes in OA, recent work has highlighted inertial sensors ability to measure more advanced outcomes such as knee joint angle, KAM, and impact accelerations, as well as a variety of variability and symmetry measures. Nevertheless, there remains a need for more longitudinal study designs, patient-specific models, free-living assessments, and a push for “Code Reuse” to maximize the unique capabilities of these devices and ultimately improve how we diagnose and treat this debilitating disease.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Wearable Inertial Sensors for Gait Analysis in Adults with Osteoarthritis-A Scoping Review.

Our objective was to conduct a scoping review which summarizes the growing body of literature using wearable inertial sensors for gait analysis in lower limb osteoarthritis. We searched six databases using predetermined search terms which highlighted the broad areas of inertial sensors, gait, and osteoarthritis. Two authors independently conducted title and abstract reviews, followed by two authors independently completing full-text screenings. Study quality was also assessed by two independent raters and data were extracted by one reviewer in areas such as study design, osteoarthritis sample, protocols, and inertial sensor outcomes. A total of 72 articles were included, which studied the gait of 2159 adults with osteoarthritis (OA) using inertial sensors. The most common location of OA studied was the knee (n = 46), followed by the hip (n = 22), and the ankle (n = 7). The back (n = 41) and the shank (n = 40) were the most common placements for inertial sensors. The three most prevalent biomechanical outcomes studied were: mean spatiotemporal parameters (n = 45), segment or joint angles (n = 33), and linear acceleration magnitudes (n = 22). Our findings demonstrate exceptional growth in this field in the last 5 years. Nevertheless, there remains a need for more longitudinal study designs, patient-specific models, free-living assessments, and a push for “Code Reuse” to maximize the unique capabilities of these devices and ultimately improve how we diagnose and treat this debilitating disease.

Video analysis of high-magnitude head impacts in men’s collegiate lacrosse

Background/aimLacrosse is one of the fastest growing sports in the USA. Efforts to minimise head injuries focus on promoting safe play through player and coach education, rules enforcement and use...

Effects of tilt of the gravito-inertial acceleration vector on the angular vestibuloocular reflex during centrifugation.

Effects of tilt of the gravito-inertial acceleration vector on the angular vestibuloocular reflex during centrifugation. Interaction of the horizontal linear and angular vestibuloocular reflexes (lVOR and aVOR) was studied in rhesus and cynomolgus monkeys during centered rotation and off-center rotation at a constant velocity (centrifugation). During centered rotation, the eye velocity vector was aligned with the axis of rotation, which was coincident with the direction of gravity. Facing and back to motion centrifugation tilted the resultant of gravity and linear acceleration, gravito-inertial acceleration (GIA), inducing cross-coupled vertical components of eye velocity. These components were upward when facing motion and downward when back to motion and caused the axis of eye velocity to reorient from alignment with the body yaw axis toward the tilted GIA. A major finding was that horizontal time constants were asymmetric in each monkey, generally being longer when associated with downward than upward cross coupling. Because of these asymmetries, accurate estimates of the contribution of the horizontal lVOR could not be obtained by simply subtracting horizontal eye velocity profiles during facing and back to motion centrifugation. Instead, it was necessary to consider the effects of GIA tilts on velocity storage before attempting to estimate the horizontal lVOR. In each monkey, the horizontal time constant of optokinetic after-nystagmus (OKAN) was reduced as a function of increasing head tilt with respect to gravity. When variations in horizontal time constant as a function of GIA tilt were included in the aVOR model, the rising and falling phases of horizontal eye velocity during facing and back to motion centrifugation were closely predicted, and the estimated contribution of the compensatory lVOR was negligible. Beating fields of horizontal eye position were unaffected by the presence or magnitude of linear acceleration during centrifugation. These conclusions were evaluated in animals in which the low-frequency aVOR was abolished by canal plugging, isolating the contribution of the lVOR. Postoperatively, the animals had normal ocular counterrolling and horizontal eye velocity modulation during off-vertical axis rotation (OVAR), suggesting that the otoliths were intact. No measurable horizontal eye velocity was elicited by centrifugation with angular accelerations </=40 degrees /s2 and angular velocities </=400 degrees /s. We conclude that in rhesus and cynomolgus monkeys, differences between horizontal eye velocities recorded during facing and back to motion constant velocity centrifugation can be explained by orienting effects of the GIA tilt on the time constants of the horizontal aVOR and not by a superposed lVOR.

Gaze strategies during linear motion in head-free humans.

1. Eye-head coordination strategies during horizontal displacements along the y (interaural) axis were investigated in human subjects seated on a sled (linear accelerator device) and tested in head-free conditions. They were instructed to stabilize their gaze, while in motion, on an earth-fixed memorized target and then, after cart immobilization, to look again at the real target. The last part of the test required a corrective saccade, which enabled us to evaluate the error of the subject's displacement estimation. Eye and head compensatory reflexes were tested within the 0.001-0.2 g acceleration range with a sinusoidal motion amplitude of 0.8 m peak to peak. 2. Fixation stabilization on a memorized target was achieved by different eye-head coordination strategies. According to the relative contribution of eye and head motion, a continuum among individual strategies was observed, covering a range of head contributions varying from 0 to almost 100%. All these strategies were well adapted because they contributed to the counteraction of the displacement and led to an optimal gaze accuracy. 3. The use of various gaze strategies during linear motion to achieve the same movement differed according to the subject, but also depended upon motion kinematics. As a rule, head contribution increased as the magnitude of linear acceleration was enhanced. 4. Different eye-head coordination strategies implicated either a linear vestibulo-ocular reflex (LVOR) or ocular responses composed of a combination of antagonistic angular and linear vestibulo-ocular reflexes (AVOR-LVOR). The slow phase direction of these two oculomotor responses for fixation stabilization on the target were compensatory and anticompensatory, respectively. 5. One of the major points of this study was the contribution of the saccadic system to gaze strategies, even in our experimental conditions where the head was free to move. We concluded that vestibular-saccadic cooperation appears to be a common feature in the elaboration of adequate fixation stabilization in daily life situations. 6. The functional coupling of these various subsystems involved in fixation stabilization depended on the range of motion: while the acceleration increased, the saccadic eye movements were replaced by vestibulo-ocular responses whose slow phase direction was opposite that of head motion and, therefore, directed away from the target. 7. Fast components of the nystagmic pattern of eye movements were able to improve gaze position accuracy, bringing the eyes toward the memorized target.(ABSTRACT TRUNCATED AT 400 WORDS)