Triaxial Accelerometer System Research Articles

Multi-Sensor Combined Measurement While Drilling Based on the Improved Adaptive Fading Square Root Unscented Kalman Filter.

In the process of the attitude measurement for a steering drilling system, the measurement of the attitude parameters may be uncertain and unpredictable due to the influence of server vibration on bits. In order to eliminate the interference caused by vibration on the measurement and quickly obtain the accurate attitude parameters of the steering drilling tool, a new method for multi-sensor dynamic attitude combined measurement is presented. Firstly, by using a triaxial accelerometer and triaxial magnetometer measurement system, the nonlinear model based on the quaternion is established. Then, an improved adaptive fading square root unscented Kalman filter is proposed for eliminating the vibration disturbance signal. In this algorithm, the square root of the state covariance matrix is used to replace the covariance matrix in the classical unscented Kalman filter (UKF) to avoid the filter divergence caused by the negative definite state covariance matrix. The fading factor is introduced into UKF to adjust the filter gain in real-time and improve the adaptive ability of the algorithm to mutation state. Finally, the computational method of the fading factor is optimized to ensure the self-adaptability of the algorithm and reduce the computational complexity. The results of the laboratory test and the field-drilling data show that the proposed method can filter out the interference noise in the attitude measurement sensor effectively, improve the solution accuracy of attitude parameters of drilling tools in the case of abrupt changes in the measuring environment, and thus ensuring the dynamic stability of the well trajectory.

Triaxial accelerometer evaluation is correlated with IKDC grade of pivot shift.

The purpose of this study was to evaluate the correlation between tibial acceleration parameters measured by the KiRA device and the clinical grade of pivot shift. The secondary objective was to report the risk factors for pre-operative high-grade pivot shift. Two-hundred and ninety-five ACL deficient patients were examined under anesthesia. The pivot shift tests were performed twice by an expert surgeon. Clinical grading was performed using the International Knee Documentation Committee (IKDC) scale and tibial acceleration data was recorded using a triaxial accelerometer system (KiRA). The difference in the tibial acceleration range between injured and contralateral limbs was used in the analysis. Correlation coefficients were calculated using linear regression. Multivariate logistic regression was used to identify risk factors for high grade pivot shift. The clinical grade of pivot shift and the side-to-side difference in delta tibial acceleration determined by KiRA were significantly correlated (r = 0.57; 95% CI 0.513-0.658, p < 0.0001). The only risk factor identified to have a significant association with high grade pivot shift was an antero-posterior side to side laxity difference > 6mm (OR = 2.070; 95% CI (1.259-3.405), p = 0.0042). Side-to-side difference in tibial acceleration range, as measured by KiRA, is correlated with the IKDC pivot shift grade in anaesthetized patients. Side-to-side A-P laxity difference greater than 6mm is reported as a newly defined risk factor for high grade pivot shift in the ACL injured knee. Level II.

Kinetics and perception of basketball landing in various heights and footwear cushioning.

BackgroundThe previous studies on basketball landing have not shown a systematic agreement between landing impacts and midsole densities. One plausible reason is that the midsole densities alone used to represent the cushioning capability of a shoe seems over simplified. The aim of this study is to examine the effects of different landing heights and shoes of different cushioning performance on tibial shock, impact loading and knee kinematics of basketball players.MethodsNineteen university team basketball players performed drop landings from different height conditions (0.45m vs. 0.61m) as well as with different shoe cushioning properties (regular, better vs. best-cushioned). For each condition, tibial acceleration, vertical ground reaction force and knee kinematics were measured with a tri-axial accelerometer, force plate and motion capture system, respectively. Heel comfort perception was indicated on the 150-mm Visual Analogue Scale. A 2 (height) x 3 (footwear) ANOVA with repeated measures was performed to determine the effects of different landing heights and shoe cushioning on the measured parameters.ResultsWe did not find significant interactions between landing height and shoe conditions on tibial shock, impact peak, mean loading rate, maximum knee flexion angle and total ankle range of motion. However, greater tibial shock, impact peak, mean loading rates and total ankle range of motion were determined at a higher landing height (P < 0.01). Regular-cushioned shoes demonstrated significantly greater tibial shock and mean loading rate compared with better- and best-cushioned shoes (P < 0.05). The correlation analysis indicated that the heel comfort perception was fairly associated with impact peak and mean loading rate regardless of heights (P < 0.05), but not associated with tibial shock.ConclusionsDetermination of shoe cushioning performance, regardless of shoe midsole materials and constructions, would be capable in order to identify optimal shoe models for better protection against tibial stress fracture. Subjective comfort rating could estimate the level of impact loading in non-laboratory based situations.

Do running speed and shoe cushioning influence impact loading and tibial shock in basketball players?

BackgroundTibial stress fracture (TSF) is a common injury in basketball players. This condition has been associated with high tibial shock and impact loading, which can be affected by running speed, footwear condition, and footstrike pattern. However, these relationships were established in runners but not in basketball players, with very little research done on impact loading and speed. Hence, this study compared tibial shock, impact loading, and foot strike pattern in basketball players running at different speeds with different shoe cushioning properties/performances.MethodsEighteen male collegiate basketball players performed straight running trials with different shoe cushioning (regular-, better-, and best-cushioning) and running speed conditions (3.0 m/s vs. 6.0 m/s) on a flat instrumented runway. Tri-axial accelerometer, force plate and motion capture system were used to determine tibial accelerations, vertical ground reaction forces and footstrike patterns in each condition, respectively. Comfort perception was indicated on a 150 mm Visual Analogue Scale. A 2 (speed) × 3 (footwear) repeated measures ANOVA was used to examine the main effects of shoe cushioning and running speeds.ResultsGreater tibial shock (P < 0.001; η2 = 0.80) and impact loading (P < 0.001; η2 = 0.73–0.87) were experienced at faster running speeds. Interestingly, shoes with regular-cushioning or best-cushioning resulted in greater tibial shock (P = 0.03; η2 = 0.39) and impact loading (P = 0.03; η2 = 0.38–0.68) than shoes with better-cushioning. Basketball players continued using a rearfoot strike during running, regardless of running speed and footwear cushioning conditions (P > 0.14; η2 = 0.13).DiscussionThere may be an optimal band of shoe cushioning for better protection against TSF. These findings may provide insights to formulate rehabilitation protocols for basketball players who are recovering from TSF.

Framework of Data Acquisition and Integration for the Detection of Pavement Distress via Multiple Vehicles

AbstractStreet defects, such as potholes and sunken manholes, in general develop quickly compared to other pavement distresses, such as cracking and rutting. Those street defects can result in vehicle damage. This paper proposes an automated and innovative method to obtain up-to-date information about those street defects with the use of a mobile data collection kit mounted on vehicles. In each mobile data collection kit, a triaxial accelerometer and global positioning system sensor collect data for the detection of street defects. A local algorithm is embedded in the mobile data collection kit to increase the efficiency of a local data logging process and to perform a preliminary detection of street defects. At a back-end server, a more precise street defect detection algorithm enhances the performance of the proposed monitoring system by integrating data collected from multiple sensor-equipped vehicles. The street defect detection algorithm at the back-end server relies on a supervised machine learning ...

Test-Retest Reliability and Concurrent Validity of a Single Tri-Axial Accelerometer-Based Gait Analysis in Older Adults with Normal Cognition.

ObjectiveWe investigated the concurrent validity and test-retest reliability of spatio-temporal gait parameters measured with a single tri-axial accelerometer (TAA), determined the optimal number of steps required for obtaining acceptable levels of reliability, and compared the validity and reliability of the estimated gait parameters across the three reference axes of the TAA.MethodsA total of 82 cognitively normal elderly participants walked around a 40-m long round walkway twice wearing a TAA at their center of body mass. Gait parameters such as cadence, gait velocity, step time, step length, step time variability, and step time asymmetry were estimated from the low pass-filtered signal of the TAA. The test-retest reliability and concurrent validity with the GAITRite® system were evaluated for the estimated gait parameters.ResultsGait parameters using signals from the vertical axis showed excellent reliability for all gait parameters; the intraclass correlation coefficient (ICC) was 0.79–0.90. A minimum of 26 steps and 14 steps were needed to achieve excellent reliability in step time variability and step time asymmetry, respectively. A strong level of agreement was seen for the basic gait parameters between the TAA and GAITRiteⓇ (ICC = 0.91–0.96).ConclusionsThe measurement of gait parameters of elderly individuals with normal cognition using a TAA placed on the body’s center of mass was reliable and showed superiority over the GAITRiteⓇ with regard to gait variability and asymmetry. The TAA system was a valid tool for measuring basic gait parameters. Considering its wearability and low price, the TAA system may be a promising alternative to the pressure sensor walkway system for measuring gait parameters.

Empowering sedentary adults to reduce sedentary behaviour: Success with a technology-based physical activity monitor

Background: In many societies, increased attention is being paid todeveloppotential interventionmethods that focusonreducing sedentary time and increasing physical activity levels. This study aimed to assess the effectiveness of a 4-week intervention in which an online personal activitymonitor (Gruve-TechnologiesTM) was used to reduce sedentary behaviour among sedentary adults during free-living activities. The monitor is a tri-axial accelerometer system that tracks time spent on daily activities via a wearable device and an accompanying online service. The device monitors a participant’s daily physical activity at 20Hz and stores the minute data on the device for uploading later to the interactive online software. These data subsequently provide the user with an easy-to-understand visualization of daily activity patterns. Goalsetting features are activated alongside simple graphs and charts to enhance the self-monitoring of energy expenditure. An indicator (a halo bar) on top of the device also highlights the users’ progress towards their daily goal. When palpated throughout the day, the indicator bar provides a light-emitting diode colour corresponding to the user’s progress towards their daily activity goal. Method: Eighteen sedentary adults (12 men, 6 women, mean age± SD, 29±4.0 year) volunteers were recruited to participate in the study. Time spent in sedentary and light-, moderate-, and vigorous-intensity physical activity and energy expenditure were assessed during waking hours using the monitor at baseline and post-intervention. Results: A significant decrease of 33% (3.1h/day) was found between the time spent in sedentary activities measured at baseline (9.4±1.1h/day) and at the end of the 4-week intervention (6.3±0.8h/day (p<0.001). Between baseline and the end of the 4-week intervention, significant increases (p<0.001) were found in the amount of time spent on light-intensity (45% [2.6h/day]), moderate-intensity (33% [1h/day]), and energy expenditure (47% [216.7 kcal/day]). A significant increase (p<0.05) was found in the amount of time spent on vigorous-intensity physical activity (39% [0.16h/day]). Discussion: This lifestyle study involving sedentary adults suggests that, when engaging with the online personal activity monitor, individuals decreased (33%) the amount of time they spent in sedentary activities. Such a large reduction in the amount of time spent in sedentary activities has not been previously published. Additionally, participants increased their daily lightand moderate-intensity physical activity and energy expenditure. These results may be considered a step toward development of a meaningfully positive active lifestyle.

Measurement of the Wheelchair-Operating Time Spent by Stroke Patients Using a New Triaxial Accelerometer System

Purpose: We investigated the validity of a triaxial accelerometer system for measuring the time spent lying down, sitting, standing, walking, and operating a wheelchair by control subjects and stroke patients in a convalescence ward. Methods: Physical activities were measured using a new triaxial accelerometer system (A-MES; Activity Monitoring and Evaluation System) that consists of two sensors, a station, and analytical software used with a personal computer. In Experiment 1, the times that the healthy subjects (n = 12) spent operating a wheelchair, lying down, sitting, standing, and walking were measured both by the A-MES and by videotaping (video time). In Experiment 2, the amounts of time spent by the stroke patients not able to walk without support (n = 30) as they were lying down, sitting, standing, walking, and operating a wheelchair were measured by the A-MES. Results: The time spent operating a wheelchair measured with the A-MES was significantly correlated with the video time in the healthy subjects. The stroke patients’ average times (minutes) of total, operating a wheelchair, lying down, sitting, standing, and walking were 601.0 ± 18.1, 57.1 ± 28.8, 265.0 ± 86.3, 263.3 ± 60.6, 7.8 ± 7.0, and 7.7 ± 6.0, respectively. Conclusions: The A-MES accurately evaluated the stroke patients’ time spent operating a wheelchair. The stroke patients’ mean time spent operating a wheelchair over the course of one day was 57.1 ± 28.8 min in a Center for Rehabilitation.

Evaluation of walking time according to walking speed using a triaxial accelerometer system

Miura S, Satake M, Tamura Y, Ikeda M, Kawagoshi A, Sugawara K, Takahashi H, Homma M, Sakata S, Shioya T. Evaluation of walking time according to walking speed using a triaxial accelerometer system. Jpn J Compr Rehabil Sci 2013; 4: 73−79. Purpose: The primary purpose of this study was to quantify the walking time in daily life as slow and fast walking times using a newly improved triaxial accelerometer system. The secondary purpose was to study the slow and fast walking times of healthy young and elderly adults and stable patients with chronic obstructive pulmonary disease (COPD) using this system. Methods: Twenty-six healthy young subjects, 15 healthy elderly adults, and 11 stable COPD patients participated in this study. The subjects’ time spent walking, standing, sitting, and lying down were assessed using an activity monitoring and evaluation system (A-MESTM). We evaluated the slow and fast walking times according to changes in the detection threshold in the system’s software. Results: The distinguishing speed was found to be 2 km/h, and thus we divided the subjects’ walking time into slow (<2 km/h) and fast (≥2 km/h) walking using 2 km/h to distinguish the speed. Ninety-five percent of the walking measured by the A-MESTM was slow walking. The fast walking time of the stable COPD patients was significantly shorter than that of the healthy young and elderly adults (p<0.01). Conclusion: These results suggest that walking time in daily life can be differentiated as slow (<2 km/h) and fast (≥2 km/h) walking using a new triaxial accelerometer system.

Quantitative assessment of walking time and postural change in patients with COPD using a new triaxial accelerometer system

BackgroundThe purpose of this study was to quantify the walking time and frequency of postural changes in daily life in patients with chronic obstructive pulmonary disease (COPD) using a new triaxial accelerometer system.MethodsTwenty-six elderly patients with stable COPD (age 76.8 ± 6.2 years; percent forced expiratory volume in one second [%FEV1] 52.9% ± 26.3%) and 20 age-matched elderly subjects (age 73.0 ± 4.2 years; %FEV1 124.0% ± 22.3%) participated in the study. The subjects’ time spent walking (slow, fast), standing, sitting, and lying down and the frequency of their postural changes (getting up, standing up) were assessed for 7 consecutive days using an Activity Monitoring And Evaluation System (A-MES™). We analyzed the relationships among walking times, frequency of postural changes, and physiologic factors in both COPD patients and controls.ResultsThe COPD patients’ total walking time, including slow (<2 km/hour) and fast (≥2 km/hour) walking, and their frequency of standing up were significantly lower than those of the age-matched controls (P < 0.01). The fast walking time in daily life was significantly correlated with the 6-minute walking distance, quadriceps femoris muscle force, and dyspnea (P < 0.01).ConclusionThese results suggest that both slow (<2 km/hour) and fast (≥2 km/hour) walking time and frequency of postural changes is significantly decreased in COPD patients compared with healthy elderly subjects. The data also suggest that the COPD patients’ different walking times in daily life are significantly correlated with exercise capacity and dyspnea. The 6-minute walking distance had the strongest correlation with fast walking time.

Comparison of three non-invasive quantitative measurement systems for the pivot shift test

The purpose of this study was to evaluate three different non-invasive measuring devices for the pivot shift phenomenon with reference to direct bony movement measured by an electromagnetic device rigidly attached to the tibia and femur. A lower body cadaveric specimen was prepared to create a positive pivot shift in both knees. Twelve expert knee surgeons from worldwide performed their preferred pivot shift technique three times in each knee. After watching an instructional video, the examiners used a standardized technique to perform three additional pivot shift maneuvers in each knee. An electromagnetic tracking system, rigidly attached to femur and tibia, was used to provide reference measurements during the pivot shift test. Three different devices were correlated to the reference method and evaluated in this study: (1) Electromagnetic tracking system with skin sensors; (2) Triaxial accelerometer system; (3) Simple image analysis. When results from both pivot shift techniques (preferred and standardized) were combined, the electromagnetic tracking system with skin sensors showed positive correlation with the reference measurement for acceleration and translation parameters (r=0.88 and r=0.67, respectively; both P<0.01); The triaxial accelerometer system demonstrated good correlation with the reference measurement for acceleration (r=0.75; P<0.001). The image analysis system was poorly correlated to the translation of the reference measurement (r=0.24; P<0.01). The electromagnetic tracking system with skin sensors provided the best correlation with the reference method. The triaxial accelerometer showed also a good correlation and the image analysis system showed a positive, but poor correlation with the reference method. More research is needed in order to validate simple and non-invasive devices for clinical application.

Clinical grading of the pivot shift test correlates best with tibial acceleration

Recently, different measurement systems have been developed to quantitatively measure the pivot shift in vivo. These systems lack validation and a large inter-examiner variability for the manually performed pivot shift test exists. The purpose of this study was to perform objective measurements of the pivot shift using three different measurement devices and to examine the correlation of the measurements with clinical grading of the pivot shift. A cadaver knee on a whole lower body specimen was prepared to display a high-grade pivot shift. The pivot shift tests were performed three times by 12 blinded expert surgeons using their preferred technique. Simultaneous data samplings were recorded using three different measurement devices: (1) electromagnetic tracking system using bone-attached and skin-fixed sensors, respectively, (2) triaxial accelerometer system, and (3) simple image analysis. The surgeons graded the knee clinically using pivot shift grades I-III. Correlations were calculated using the Spearman's rank correlation coefficient. The expert surgeons average clinical grading was 2.3 (SD±0.5). Clinical grading displayed best correlation with the acceleration of reduction as measured by electromagnetic tracking system with bone-attached sensors (r=0.67, P<0.05). Similar correlation coefficient was found for the acceleration of reduction (r=0.58, P=0.05) and the "jerk" component of acceleration (r=0.61, P<0.05) measured by means of the triaxial accelerometer system. The pivot shift can be quantified by several in vivo measurement devices. Best correlation with clinical grading was found with tibial acceleration parameters. Future studies will have to analyze how quantitative parameters can be utilized to standardize clinical grading of the pivot shift. Diagnostic study, Level II.

Comparison of Accelerometer Based Vertical Jump Assessments to a Linear Position Transducer Plus Force Plate System

The vertical jump is a commonly used test by strength and conditioning professionals. However, without access to force plates and/or linear position transducers, force-time curve characteristics of a vertical jump cannot be evaluated. Recently, accelerometer technology has been developed that may serve as a means for more robust field based testing. However, there are very little data on the validity of these devices. PURPOSE: To compare accelerometer based assessments of countermovement vertical jump performance against a force plate and linear position transducer system. METHODS: Ten college aged men (age = 23.63.1 y; height = 180.16.3 cm; mass = 85.015.2kg; body fat = 14.26.5%) performed two series of five restricted (no arm swing) zero load countermovement vertical jumps. Subjects each performed each jump on a force plate while holding a PVC pipe that was attached to two linear position transducers, both of which sampled at 1000 Hz. Additionally, a triaxial accelerometer which sampled at 500 Hz was attached to the PVC pipe. The force plate was used to determine peak force (PF), rate of force development (RFD), and flight time (FT), while the linear position transducers were used to determine vertical displacement (VD) and peak velocity (PV). The force and velocity data were then utilized to calculate the peak power output (PP) achieved during the vertical jump. All force plate and linear position transducer data were derived with the use of a custom LabView Program. The accelerometer was used to assess vertical acceleration, from which PF, RFD, VD, FT and PP were derived and resampled with the use of a custom Labview program. Accelerometer data was resampled from 500 Hz to 250 Hz, 125 Hz and 50 Hz. Paired comparisons coupled with a Holm's Sequential Bonferroni were used to compare all accelerometer based measures to the force plate and linear position transducer system. Additionally, Pearson Product Moment correlations were made between the various assessment systems. Percent differences and coefficients of variance were also calculated between the two systems. RESULTS: The accelerometer system resulted in a significant (p 0.70) to the force plate and linear position transducer system for PF, RFD, PP, FT, and VD at both 500 and 250 Hz sampling rates. The difference between the force plate plus linear position transducer system and the accelerometer exhibits a general increasing trend as the sampling rate of the accelerometer is decreased. CONCLUSION: The triaxial accelerometer system tested in the present study overestimates PF, RFD, PP, FT and VD when compared to a force plate plus linear position transducer system that samples at 1000 Hz. PRACTICAL APPLICATIONS: When comparing vertical jump data collected with an accelerometer to the scientific literature, it is important to note that PF, RFD, PP, FT and VD are consistently overestimated. ACKNOWLEDGMENTS: This investigation was partially supported by MyoTest Inc., which donated the accelerometer system used in this investigation.

Head movements during two computer work tasks assessed by accelerometry

We investigated whether potential differences in head inclinations and accelerations for two highly similar computer work tasks could be detected using (1) a triaxial accelerometer and (2) a simulated uniaxial accelerometer. Ten subjects’ head movements were registered with a triaxial accelerometer system for two similar document-management tasks at their work place: a fully electronic document-management task and one also involving paper documents. In situations where head movements were small, a triaxial accelerometer was able to discriminate between the different degrees of static work of the neck in terms of range of head inclinations and accelerations. A difference in head acceleration was also found by using a simulated uniaxial accelerometer. Thus, in terms of head movement and for work similar to this office work, potential dynamic differences in observationally similar work tasks can be investigated by using a triaxial accelerometer. For acceleration alone, a uniaxial accelerometer can also be used.

Reproducibility of spatio-temporal gait parameters under different conditions in older adults using a trunk tri-axial accelerometer system

The aim of this study was to determine intra- and interrater reliability of spatio-temporal gait parameters on different walking surfaces and under dual task conditions in an older adult population using a trunk tri-axial accelerometer (DynaPort ®MiniMod) system. Twenty-three independent living, older subjects (8 males, 15 females) aged 73.4 ± 4.3 years walked three times at their preferred walking speed in two test sessions under four different conditions over 24 m (gymnasium floor versus soft foam rubber walkway, with both normal and dual task walking conditions). Inter- and intrarater reliability was assessed. Subsequently intraclass correlation coefficients (ICC), coefficients of variation (CV) and ratios limits of agreement (RLOA) were calculated. The reliability of walking speed, cadence, step duration and step length was excellent with high ICCs and small CVs and RLOAs. ICCs of gait variability ranged from 0.12 to 0.88. The corresponding CVs ranged from 12% to 34% and RLOAs from 35% to 93% and appeared relatively large. The results of this study demonstrate that walking speed, cadence, step duration and step length under more challenging conditions can be reliably measured in independent living older adults using the DynaPort ®MiniMod system. Gait variability measures need to be viewed with caution and further research in older populations is needed to determine the value of these parameters derived from this measurement system.

Concurrent validity of a trunk tri-axial accelerometer system for gait analysis in older adults

The aim of this study was (1) to determine the concurrent validity of a trunk tri-axial accelerometer system (DynaPort ®MiniMod) with the GAITRite ® system for spatio-temporal gait parameters at preferred, slow and fast self-selected walking speed that were recorded for averaged and individual step data in an older adult population and (2) to compare the levels of agreement for averaged step data from different walking distances and individual step data. The levels of agreement between the two systems for averaged step data was excellent for walking speed, cadence, step duration and step length (intraclass correlation coefficients (ICCs) between 0.99 and 1.00, ratios limits of agreement (RLOA) between 0.7% and 3.3%), moderate for variability of step duration (ICCs between 0.88 and 0.98 and RLOAs between 19% and 34%) and low for variability of step length (ICCs between 0.24 and 0.33 and RLOAs between 73% and 87%). The levels of agreement for individual step duration and step length were moderate with ICCs between 0.81 and 0.89 and with RLOAs between 9% and 13%. Comparing RLOAs from averaged step data across the different walking distances and individual step data, the RLOAs decreased with increased number of steps. The results of this study demonstrate that the DynaPort ®MiniMod system, which allows measurements in real life conditions, is a highly valid tool for assessment of spatio-temporal gait parameters for averaged step data across a walkway length of approximately 20 m in independent living elderly. Gait variability measures and individual step data need to be viewed with caution because of the moderate to low levels of agreement between the two systems.

The development of a method to measure head acceleration and motion in high-impact crashes.

To establish a mechanism to obtain precise measurements of the accelerations of the head in the high-speed racing environment and during crash impacts. The long-term goal is to apply this system to the assessment of head injury in automobile racing drivers and then in participants in other helmeted sports. A multidisciplinary team conceptualized, designed, and successfully tested a triaxial accelerometer system capable of measuring head acceleration and motion in high-impact crashes. The system has been implemented successfully in the professional racing environment. Accurate and reproducible data have been obtained from the accelerometer system in tests on manikins and cadavers and in actual racing events. The system has been implemented in two professional racing series in 2003. Information gained from the accelerometer system is currently being entered into a database. Eventually, the data should aid in the development of improved cockpit head protection in racing cars. Improved helmet design not only in motor sports but also in other helmeted sports should benefit from the data collected. These data will also aid the development of improved head injury protection in military aircraft and passenger vehicles. Although there has been a significant decrease in the overall rate of injury during the past 25 years, head injury remains a serious safety concern in motor sports and the greatest cause of death. Sports-related head injuries are also of great concern because repeated mild head injury has become an important health issue with potential long-term disability. True human tolerance to brain injury has yet to be established. Our scientific knowledge of brain injury is currently based on results derived from manikin, cadaver, and human volunteer testing, along with animal and computer models. The racing environment represents a venue to ethically measure and evaluate the forces involved in human brain injury.

718 三軸加速度センサー・インパルスハンマーシステムを用いた伸張反射の定量解析(筋肉の反応とスポーツ機器,OS-23 ヒューマン・ダイナミクス(2))

718 三軸加速度センサー・インパルスハンマーシステムを用いた伸張反射の定量解析(筋肉の反応とスポーツ機器,OS-23 ヒューマン・ダイナミクス(2))

METHODOLOGY FOR DETERMINING ALMOND SHAKER DISPLACEMENT AND FREQUENCY

A triaxial accelerometer system was developed to reliably estimate the frequency and displacement characteristicsof commercial almond trunk shakers. The estimated displacement and frequency in the horizontal (xy) plane were similarto values that have been previously reported for commercial trunk shakers, but a substantial displacement was also found inthe vertical direction. Vertical displacements in mechanical tree shakers have not been previously reported and may representan important source of mechanical injury to the bark and the root system of almond trees.

Validation of the Tracmor triaxial accelerometer system for walking.

Walking is likely to contribute substantially to nonexercise activity thermogenesis. The Tracmor triaxial accelerometer system (Maastricht, The Netherlands) is the most widely validated system for detecting body movement in free-living subjects. The aim of this study was to validate the Tracmor triaxial accelerometer system for estimating the energy expenditure of walking. Experiments were conducted in healthy subjects. First, baseline variability for Tracmor output was determined for subjects standing still. Second, Tracmor output was compared for walking on a treadmill and on level ground. Third, both Tracmor output and energy expenditure were compared for walking on a treadmill and walking on level ground. Finally, the effect of gradient on Tracmor output and energy expenditure was compared for subjects walking on a treadmill. The data demonstrated excellent reproducibility for comparing Tracmor output for standing (CV < 2%). There were excellent log-linear relationships between velocity and Tracmor output walking on a treadmill (r = 0.998) and on level ground (r = 0.999). Tracmor output and the energy expenditure of walking were inseparable for the two modalities of walking. However, the variance in response was such that to reliably derive the relationship between Tracmor output and energy expenditure, separate regression equations are needed for each subject. Finally, the Tracmor accelerometer did not detect the increased energy expenditure of walking that occurs as gradient increases. The Tracmor triaxial accelerometer provides reproducible and reliable data on the body motion associated with walking regardless of whether a subject walks on a treadmill or level ground. Tracmor units can be used to predict the energetic cost of walking provided that separate regression equations are derived for each subject to convert Tracmor output to energy expenditure.