Accelerometric System Research Articles

The contribution of plyometric exercises assisted by sensory technology on vertical jump parameters in U15 female volleyball players

Background and Study Aim. Volleyball requires high vertical jump skills for crucial actions like attacking and blocking, making jump training a focus for players, especially in youth categories. The main goal of the study was to highlight (with some specific data) the strengths and weaknesses of integrating sensory technology into the physical training program, during the entire competitive period. Material and Methods. The study included both an experimental and a control group, each consisting of 16 female athletes from the volleyball section of the Cetate Sports High School in Deva. During the competitive season of 2022/2023, both groups underwent daily training sessions from Monday to Saturday, totaling 120 minutes per day. The BlazePod Flash Reflex Training system was employed in this research. It integrates cognitive training to enhance thinking speed and clarity with physical exercises aimed at maximizing motor skills. Performance evaluations of the athletes utilized eight predefined tests from the OptoJump Next optical measuring system and the Myotest accelerometric system. To analyze the data, paired (dependent) sample t-tests were conducted to compare average parameters between matched samples. Repeated measures ANOVA was utilized to compare the average outcomes, ensuring the participants were consistent across the evaluated conditions. Results. The experimental group showed significant improvements in the height reached from the center of gravity and flight time for the following tests: Countermovement Jump, Countermovement Jump with Arm Swing, Squat Jump, Squat Jump with Arm Swing, and Drop Jump from 30 cm. All improvements reached statistical significance: p<0.05. Significant enhancements were also observed in average jump height, jump power, force of jumps, and ascensional speed, demonstrating statistical significance (p<0.05). Furthermore, the use of an arm swing during jumps notably improved performance compared to when jumps were performed with hands on hips. This indicates that an arm swing can significantly increase the height of the vertical jump (p<0.05). Conclusions. The study confirms that the integration of sensory technology into the training programs for junior volleyball teams is effective in enhancing training outcomes. This approach not only improves the vertical jump capabilities of young athletes but also positively affects their ability to perform technical moves that require elevation from the ground. It underscores the potential of innovative training methods in advancing athletic performance in youth sports.

Game Demands of a Professional Ice Hockey Team with Special Emphasis on Fatigue Development and Playing Position.

The aim of this study was to describe the game activity profile of a professional ice hockey team with special emphasis on fatigue development and playing position. Data were collected using a wearable 200-Hz accelerometric system and heart rate (HR) throughout eight official games in a professional ice hockey team (6 defensemen and 11 forwards; n = 122 files). On-ice 10- and 30-m sprint performance, repeated sprint ability and HR responses to the submaximal Yo-Yo Intermittent recovery level 1 test were assessed to determine associations with game performance. Although the 3rd period was largely longer than the 1st and 2nd periods (r = 0.56-0.59), no differences were observed between periods in activity pattern, except a moderate decline in the number of decelerations <-2 m·s-2 per min (Dec2/min) in the 2nd period for forwards (r = 0.06-0.60). Mean HR, time spent >85% HRmax (t85HR), as well as the total number of intense accelerations and decelerations were higher for defensemen. However, demands were similar when expressed relative to time on-ice, except that defenders performed more Dec2/min than forwards in all periods, whereas forwards spent more t85HR during the 2nd period (r = 0.46-0.57). Time spent on ice was inversely correlated with the total number of accelerations (Acctot), accelerations >2 m·s-2 per min (Acc2/min), total decelerations per min (Dectot/min), Dec2/min and t85HR (r = -0.63 to -0.18) and positively correlated with mean HR and peak HR (r = 0.20- 0.53). No significant correlations were found between physical fitness and game activity variables scaled by individual time on ice. Absolute acceleration and HR demands of professional ice hockey seem to differ between playing positions, but not in relation to time on ice. Further, no clear signs of fatigue were captured, possibly due to the longer duration of rest intervals in the 3rd period.

An Accelerometric Sensor System With Integrated Hydrostatic Pressure Correction to Assess Carotid Arterial Stiffness

Non-invasive evaluation of vascular stiffness has established utility in cardiovascular risk and stroke prediction. This work presents an accelerometric sensor-based system with an integrated hydrostatic pressure correction unit for arterial luminal diameter measurement and local vascular stiffness assessment. A custom-designed accelerometric patch for continuous monitoring of percutaneous acceleration plethysmogram (APG) from the common carotid artery, which could estimate the arterial wall displacement, was developed. A calibration model was established to estimate the true carotid luminal diameter waveform from the accelerometer-based arterial wall displacement signals. The system’s accuracy for carotid stiffness measurement was validated by multiple in-vivo human subject studies and compared against a clinical-grade B-mode ultrasound imaging system. Accelerometric-derived carotid diameter waveform morphologically replicated the anachrotic, and dicrotic limb of the true carotid diameter recorded using reference devices. The group-average baseline value of measured carotid end-diastolic diameter and distension was 5.81 ± 0.53 mm and 0.51 ± 0.15 mm with a maximum observed beat-by-beat variation of 6.5% and 9%, respectively. Accelerometer-based vascular stiffness measures showed a significant correlation (R2 > 0.88, P < 0.0001), and clinically acceptable agreement with a reference standard imaging system. APG derived carotid stiffness indices demonstrated the capability to detect expected age-associated changes in stiffness. The study revealed that the accelerometric sensor system offers a reliable, cost-effective method for long-term non-invasive monitoring of location-specific vascular stiffness measures with potential applications in ambulatory healthcare monitors.

P.40 Ambulatory Measurement of Carotid Stiffness with a Novel Accelerometric System

PurposeArterial stiffness is a well-established marker for cardiovascular health assessment. Current methods rely on expensive imaging systems and specialised operators to perform local stiffness evaluation from the common carotid artery (CCA) and cannot be used for ambulatory monitoring in chronic disease management. In this study, we compare the performance of a novel accelerometric system, which performs ambulatory non-invasive CCA stiffness measurement, against an ultrasound-based stiffness monitor.MethodsThe accelerometric system with a wearable patch probe derives CCA’s diameter parameters from the skin surface vibrations arising out of the arterial wall displacement wave propagated to the skin surface. A subject-specific one-time calibration procedure is used to ensure accuracy, reliability and repeatability. Inbuilt pressure measurement unit of the system estimates blood pressure at CCA. Simultaneously obtained pressure and diameter parameters are used to evaluate various clinically accepted stiffness indices. An in-vivo study was performed on 36 subjects (20–50 years). Measured stiffness indices were compared against those obtained sequentially from an imaging system analysed using Carotid Studio.ResultsAccelerometric-derived diameter waveform was comparable to that acquired using the reference device. Measured group-average end-diastolic diameter and distension values were 5.81 ± 0.53 mm and 0.51 ± 0.15 mm, respectively. Diameter and stiffness indices (b, Ep, AC, PWV, etc.) were repeatable over continuous cycles (variability <12%). These measures significantly correlated (r2 > 0.88, p < 0.001) with an acceptable agreement. The one-time calibration remained valid for more than 12 days (error <13%).ConclusionThe study demonstrated the feasibility and essential functionality of a cost-effective method for long-term stiffness monitoring with potential applications in ambulatory healthcare devices.

Repeatability Study of Local Vascular Stiffness Measurement Using Carotid Surface Acceleration Plethysmogram.

We have developed an accelerometric system with a custom-designed patch probe and signal acquisition hardware to acquire the carotid wall displacement from the soft tissue surface for arterial stiffness evaluation. A subject-specific calibration model was developed to estimate the morphology of accurate carotid diameter waveform, using a standard ultrasound B-mode imaging system as the reference. Following the one-time calibration, the accelerometric system continuously acquired a non-invasive carotid lumen diameter waveform. The capability of the accelerometric system to measure the carotid stiffness index (β) in-vivo was experimentally validated by performing measurements on 8 normotensive subjects in the supine position. The repeatability and reproducibility of the results were investigated and were found to be comparable to those provided by ultrasound imaging systems. Further, the variation of arterial stiffness index measurements on different days was studied to verify the ability of the system to give a stable measure of stiffness. The accuracy of the observed results was confirmed with the state-of-art B-mode ultrasound imaging system. The results were found to be stable over a day, indicating the utility of the system for a reliable measure of non-invasive carotid arterial stiffness.

Application of an Accelerometric System for Determination of Stiffness during a Hopping Task.

Currently, there are several computational methods for stiffness during a hopping task, but they do not necessarily yield the same values. Therefore, it is essential that the simplicity of the equipment used does not affect the measurement validity. The aim of this study is to compare the stiffness values during a hopping task recorded in a laboratory environment and those acquired using the Myotest accelerometer. The measurements were performed on a group of 30 untrained female students (age: 23.0 ± 1.7 years, body height: 1.72 ± 0.07 m, and body mass: 64.8 ± 10.0 kg). According to the manual for the Myotest accelerometric system, each study participant performed three sets of 5 hops. Vertical stiffness was determined based on two measurement methods, one using the Myotest accelerometer and the other using Kistler force plates. The mean value (±SD) of vertical stiffness was 19.0 ± 9.3 kN/m in the countermovement phase and 15.1 ± 5.9 kN/m in the take-off phase. Furthermore, the stiffness determined using the Myotest was 30.7 ± 13.3 kN/m. However, significant relationships between the vertical stiffness in the countermovement phase and the Myotest stiffness (r = 0.79) and between the vertical stiffness in the take-off phase and the Myotest stiffness (r = 0.89) were found. The relationships between the vertical stiffness (in the countermovement and take-off phases) and the stiffness estimated using the Myotest allow us to conclude that despite the significantly overestimated stiffness value, the Myotest accelerometer can still be used for determination of the stiffness trends, e.g., following training. The overestimated stiffness values can result both from inaccuracy in the determination of ground contact time and flight time by the Myotest accelerometer and from the use of an equation that assumes that the movement of the center of mass has a harmonic profile.

Model Updating of Historical Belfries Based on Oma Identification Techniques

ABSTRACT Central Italy Earthquakes occurred in 2016 pointed out once more the vulnerability of Cultural Heritage (CH), especially for what concerns bell-towers since they tend to get dramatically damaged due to their considerable slenderness and deterioration, endangering their surroundings and making their preservation fundamental. This work presents the results of the study carried out on four different isolated masonry bell towers, located in Ferrara province (Italy); the parameters of the materials were deduced by calibrating Finite Element Models (FEMs) using the data collected during an investigation campaign conducted with a wired accelerometric sensor system, since it was not possible to apply destructive methodologies. Dynamic data were extracted through the application of two Operational Modal Analysis (OMA) identification techniques: the Enhanced Frequency Domain Decomposition (EFDD) and the Stochastic Subspace Identification (SSI) methodology. Particular attention was devoted to the use of MAC matrix in the validation of the mode shapes results.

Acute static stretching with different volumes improves hamstring flexibility but not reactive strength index and leg stiffness in well-trained judo athletes

Purpose: The aim of this study was to compare the effects of different volumes of static stretching exercises (SS) on the reactive strength index (RSI), leg stiffness (K leg ), and hamstring flexibility in well-trained judo athletes. Method: In total, 17 international level judo athletes (11 women and 6 men; age, 20.47 ± 1.59 years; experience in judo, 11.35 ± 1.84 years) were recruited for this study. The athletes completed three different SS sessions named low (LV–SS: 3.5 min), moderate (MV–SS: 7 min), and high volumes (HV–SS: 10.5 min), 72 h apart, in a randomized crossover study. Before and after each SS exercise session, hamstring flexibility, RSI and K leg were evaluated by a sit-and-reach test and a Myotest accelerometric system, respectively. Results: Different volumes of SS exercises improved hamstring flexibility (p .05). Different volumes of SS exercises neither improved nor reduced RSI and K leg (p > .05). Conclusion: Judo athletes can use LV–SS, MV–SS, or HV-SS for hamstring flexibility enhancement, and SS exercises can be used as a part of a warm-up session prior to judo training or competition.

Physiological, neuromuscular and perceived exertion responses in badminton games

The purpose of this study was to characterise the physiological, neuromuscular and perceived exertion variables during a badminton match and to assess the influence of these variables on the characteristics of the game. Each variable was measured before, every ten minutes, and ten and twenty minutes after a badminton game. Using a lactate device, a heart rate monitor, an accelerometric system, a dynamometer, a camera and a Borg scale, twelve games between elite players were analysed. An increase was found in the heart rate, blood lactate and in the recovery time, while a decrease was found in the power output of the lower and upper limb joints and shot frequency. These results suggest the capability of the players to preserve a high intensity of performance for as long as possible despite general fatigue. The fatigue induced by changes in physiological variables is affected more by the intensity of the stroke rather than the duration of the rallies. The perceived exertion is thought to be a combination of attentional and neuromuscular fatigue rather than related to changes in metabolites. Consequently, in future studies, researchers and trainers should consider the fatigue state as a means to increase players’ ability.

Complex processing of goniometric and acoustic signals in the automated control system of the rehabilitation exoskeleton

The technique of express-assessment of intervertebral disk changes is described. This technique is based on the automation of goniometric and arthrophonometric measurements to reduce of the trauma in the regulation and using of the rehabilitation exoskeleton. It is characterized by the application of an individual biomechanical model of a human being, built on the basis of an individual n-shaped angular model and a three-dimensional biomechanical model. The using wavelet filtering and neural network algorithms for the detection and classification of pathologies when processing of the goniometric and atrofonometric data. The developed technique is adaptive: the parameters of models and processing units are adjusted to the physiological characteristics of the patient, the neural network coefficients are automatically adjusted during the diagnostics. The processing of acoustic signals is carried out in several bands with interference compensation. Goniometric measurements are built on the basis of an accelerometric phase-metric system. A generalized structure of the influence of biochemical and biophysical factors on the change of intervertebral discs was developed.

Effect of Crossfit Training on Jump and Strength

The purpose of this study is to investigate the effect of regular CrossFit training on some force and jump parameters. 32 healthy wrestling men participated in the study, 16 experimental and 16 control groups. For the experimental group, CrossFit training, known as Cindy, was practiced three times a week for 8 weeks. The training consisted of 5 bars, 10 push-ups and 15 squats for 20 minutes. The control group continued the classical wrestling practice. Myotest accelerometric system was used for measurements of participants’ values. For the analysis of the data, repeated measure ANOVA was used. According to the results, as a result of CrossFit training, athletes' squat jump heights increased (Wilks' Lambda = .541, F (1,30) = 25, p = .00). The mean post-training leap values (33.778 ± 5.48) were higher than the pre-training leap values (32.169 ± 4.95) (p &lt;0.05). It can be concluded that Cindy CrossFit studies improve jumping and strength ability.

Validity of a contact mat and accelerometric system to assess countermovement jump from flight time

ABSTRACTCountermovement jump (CMJ) height is an important parameter in physical performance. This study compared CMJ height measured using ChronoJump contact mat (CJ) and Myotest accelerometer (MT) systems with a force platform (FP). Thirty recreationally active adults (32.1 ± 10.4 years, 75.9 ± 12.0 kg, 173.2 ± 6.3 cm) completed a CMJ protocol where height was simultaneously recorded using the three systems. CJ and MT measures were strongly and significant correlated (r = 0.65, 0.66, respectively; p < 0.05) with FP. CJ-derived measures were not significantly different to FP measures (p > 0.05), yet MT-derived measures were significantly different from those obtained using the FP (p < 0.05). Systematic bias was observed between FP and the CJ and between FP and MT. This study demonstrates the validity of CJ and MT systems for the assessment of CMJ height. Systematic bias and between-device differences in measurement should be considered when interpreting and comparing data from these devices.

Gait disturbances as specific predictive markers of the first fall onset in elderly people: a two-year prospective observational study

Falls are common in the elderly, and potentially result in injury and disability. Thus, preventing falls as soon as possible in older adults is a public health priority, yet there is no specific marker that is predictive of the first fall onset. We hypothesized that gait features should be the most relevant variables for predicting the first fall. Clinical baseline characteristics (e.g., gender, cognitive function) were assessed in 259 home-dwelling people aged 66 to 75 that had never fallen. Likewise, global kinetic behavior of gait was recorded from 22 variables in 1036 walking tests with an accelerometric gait analysis system. Afterward, monthly telephone monitoring reported the date of the first fall over 24 months. A principal components analysis was used to assess the relationship between gait variables and fall status in four groups: non-fallers, fallers from 0 to 6 months, fallers from 6 to 12 months and fallers from 12 to 24 months. The association of significant principal components (PC) with an increased risk of first fall was then evaluated using the area under the Receiver Operator Characteristic Curve (ROC). No effect of clinical confounding variables was shown as a function of groups. An eigenvalue decomposition of the correlation matrix identified a large statistical PC1 (termed “Global kinetics of gait pattern”), which accounted for 36.7% of total variance. Principal component loadings also revealed a PC2 (12.6% of total variance), related to the “Global gait regularity.” Subsequent ANOVAs showed that only PC1 discriminated the fall status during the first 6 months, while PC2 discriminated the first fall onset between 6 and 12 months. After one year, any PC was associated with falls. These results were bolstered by the ROC analyses, showing good predictive models of the first fall during the first six months or from 6 to 12 months. Overall, these findings suggest that the performance of a standardized walking test at least once a year is essential for fall prevention.

Reliability and validity of an accele-rometric system for assessing vertical jumping performance.

The validity of an accelerometric system (Myotest©) for assessing vertical jump height, vertical force and power, leg stiffness and reactivity index was examined. 20 healthy males performed 3ד5 hops in place”, 3ד1 squat jump” and 3× “1 countermovement jump” during 2 test-retest sessions. The variables were simultaneously assessed using an accelerometer and a force platform at a frequency of 0.5 and 1 kHz, respectively. Both reliability and validity of the accelerometric system were studied. No significant differences between test and retest data were found (p < 0.05), showing a high level of reliability. Besides, moderate to high intraclass correlation coefficients (ICCs) (from 0.74 to 0.96) were obtained for all variables whereas weak to moderate ICCs (from 0.29 to 0.79) were obtained for force and power during the countermovement jump. With regards to validity, the difference between the two devices was not significant for 5 hops in place height (1.8 cm), force during squat (-1.4 N · kg−1) and countermovement (0.1 N · kg−1) jumps, leg stiffness (7.8 kN · m−1) and reactivity index (0.4). So, the measurements of these variables with this accelerometer are valid, which is not the case for the other variables. The main causes of non-validity for velocity, power and contact time assessment are temporal biases of the takeoff and touchdown moments detection.

Validity of an accelerometric system for measuring force–time-based data during jumping tasks

Validity of an accelerometric system for measuring force–time-based data during jumping tasks

GAL@Home

A considerable proportion of falls occur within the domestic environment. Sensor-based identification of falls in seniors' homes could help them to remain autonomous and self-sufficient in their own homes. The objective of this study was to evaluate fall detection systems within the home environment using optical and accelerometric sensor systems. Portable triaxial accelerometers and optical sensors were used to detect falls in subjects with known problems of mobility and a recent fall history. Three subjects were investigated with the system. Overall nine falls occurred during the study period. Four falls were recorded by the accelerometric system and one fall by the optical system. Subjects with increased risk of falling as measured with mobility and fall risk assessments tend to fall more frequently. The study shows that there is a considerably large difference between fall-detector evaluation studies in domestic environments and in laboratory trials.

Validity and Reliability of the Myotest Accelerometric System for the Assessment of Vertical Jump Height

The aim of the present study was to verify the validity and reliability of the Myotest accelerometric system (Myotest SA, Sion, Switzerland) for the assessment of vertical jump height. Forty-four male basketball players (age range: 9-25 years) performed series of squat, countermovement and repeated jumps during 2 identical test sessions separated by 2-15 days. Flight height was simultaneously quantified with the Myotest system and validated photoelectric cells (Optojump). Two calculation methods were used to estimate the jump height from Myotest recordings: flight time (Myotest-T) and vertical takeoff velocity (Myotest-V). Concurrent validity was investigated comparing Myotest-T and Myotest-V to the criterion method (Optojump), and test-retest reliability was also examined. As regards validity, Myotest-T overestimated jumping height compared to Optojump (p < 0.001) with a systematic bias of approximately 7 cm, even though random errors were low (2.7 cm) and intraclass correlation coefficients (ICCs) where high (>0.98), that is, excellent validity. Myotest-V overestimated jumping height compared to Optojump (p < 0.001), with high random errors (>12 cm), high limits of agreement ratios (>36%), and low ICCs (<0.75), that is, poor validity. As regards reliability, Myotest-T showed high ICCs (range: 0.92-0.96), whereas Myotest-V showed low ICCs (range: 0.56-0.89), and high random errors (>9 cm). In conclusion, Myotest-T is a valid and reliable method for the assessment of vertical jump height, and its use is legitimate for field-based evaluations, whereas Myotest-V is neither valid nor reliable.

Influence of sensor imperfections to electronic compass attitude accuracy

Analysis of various errors of orientation and motion sensors and their influence on resulting compass attitude information are investigated and quantified in this paper. A triple-axis acceleration sensor and a triple-axis magnetic sensor are considered to form a compass module giving full orientation information (attitude). 3D-compass module with PCB-fluxgate sensors and off-shelf acceleration sensor is introduced. Three main sensor error sources are discussed separately and their contribution to final compass heading accuracy is investigated. These are sensor orthogonality error, linearity error and ADC quantization noise. The influence of these errors is simulated on artificial group of test cases which evenly covers various orientations of the compass module. It was found that the errors in the accelerometric system have major influence on the heading accuracy. It was concluded that even low-resolution AD converters may have only a minor influence on the system accuracy, while the dominant error sources are sensor triplet nonorthogonality and sensor non-linearity.

Sensitivity and specificity of a portable system measuring postural tremor.

A portable, accelerometric system measuring tremor was evaluated. That is, the validity and consistency of measurements as well as its ability to discriminate pathologic from physiological tremor were investigated. Control subjects and patients with Parkinson's disease were tested with this portable system and with an independent system that gave precise displacement data using lasers. It was found that amplitude of postural tremor as measured by the two systems differed significantly, but further investigation revealed that this difference was due 1) to the difference between amplitude of acceleration and amplitude of displacement, and 2) to changes in tremor over the time between tests, rather than to any inaccuracy or unreliability in the portable system. The other characteristics of tremor reported by the portable system were also valid and reasonably reliable in test-retest experiments, with the exception of the "harmonic index," which proved less stable. Most of the reported characteristics were distributed differently for the control group and for the patients with Parkinson's disease, but the large overlaps between distributions would make diagnosis difficult when tremor is not very pronounced. These results suggest that until better discriminating measures of tremor are available, tremor tests should be repeated and combined with other tests of motor function.