Moment of inertia of whole body using an oscillating table in adolescent boys

Association between Anthropometric Variables, Sex, and Visual Biofeedback in Dynamic Postural Control Assessed on a Computerized Wobble Board

Anthropometrics and sex influence balance performances, and visual information can change anthropometrics’ relation and the postural sway. Therefore, the aim of the present study was to evaluate the effect of anthropometric characteristics, sex, and visual biofeedback and/or their interaction on a computerized wobble board. Twenty-seven (14 females, 13 males) young adults performed three 30-s double leg stance trials on a wobble board during two conditions: with visual and without visual biofeedback. Visual biofeedback improved (p = 0.010) balance on a wobble board with respect to the condition without visual biofeedback. Regardless of sex, no differences between conditions were found (p = 0.088). When investigating the effect of anthropometrics variables, sex, and their interactions on conditions, a significant main effect of the lower limb/height ratio, sex, and their interaction on the condition without visual biofeedback was found (p = 0.0008; R2 = 0.57). For the visual biofeedback condition, significant effects for sex and body mass (p = 0.0012; R2 = 0.43) and sex and whole-body moment of inertia (p = 0.0030; R2 = 0.39) were found. Results from the present study showed (1) visual biofeedback improved wobble board balance performance; (2) a significant main effect of lower limb/height ratio, sex, and their interaction on the wobble board performances without visual biofeedback emerged; (3) significant effects were found for sex and body mass and sex and moment of inertia in the visual biofeedback condition. Findings from the present study could have an impact on training and evaluations protocols, especially when several populations such as children, athletes, older adults and people with balance disorders are involved.

Effects of acquisition device, sampling rate, and record length on kinocardiography during position-induced haemodynamic changes

BACKGROUND

Kinocardiography (KCG) is a promising new technique used to monitor cardiac mechanical function remotely. KCG is based on ballistocardiography (BCG) and seismocardiography (SCG), and measures 12 degrees-of-freedom (DOF) of body motion produced by myocardial contraction and blood flow through the cardiac chambers and major vessels.

RESULTS

The integral of kinetic energy ([Formula: see text]) obtained from the linear and rotational SCG/BCG signals was computed over each dimension over the cardiac cycle, and used as a marker of cardiac mechanical function. We tested the hypotheses that KCG metrics can be acquired using different sensors, and at 50 Hz. We also tested the effect of record length on the ensemble average on which the metrics were computed. Twelve healthy males were tested in the supine, head-down tilt, and head-up tilt positions to expand the haemodynamic states on which the validation was performed.

CONCLUSIONS

KCG metrics computed on 50 Hz and 1 kHz SCG/BCG signals were very similar. Most of the metrics were highly similar when computed on different sensors, and with less than 5% of error when computed on record length longer than 60 s. These results suggest that KCG may be a robust and non-invasive method to monitor cardiac inotropic activity. Trial registration Clinicaltrials.gov, NCT03107351. Registered 11 April 2017, https://clinicaltrials.gov/ct2/show/NCT03107351?term=NCT03107351&draw=2&rank=1 .

Cardiovascular adaptation to simulated microgravity and countermeasure efficacy assessed by ballistocardiography and seismocardiography

Head-down bed rest (HDBR) reproduces the cardiovascular effects of microgravity. We tested the hypothesis that regular high-intensity physical exercise (JUMP) could prevent this cardiovascular deconditioning, which could be detected using seismocardiography (SCG) and ballistocardiography (BCG). 23 healthy males were exposed to 60-day HDBR: 12 in a physical exercise group (JUMP), the others in a control group (CTRL). SCG and BCG were measured during supine controlled breathing protocols. From the linear and rotational SCG/BCG signals, the integral of kinetic energy ([Formula: see text]) was computed on each dimension over the cardiac cycle. At the end of HDBR, BCG rotational [Formula: see text] and SCG transversal [Formula: see text] decreased similarly for all participants (- 40% and - 44%, respectively, p < 0.05), and so did orthostatic tolerance (- 58%, p < 0.01). Resting heart rate decreased in JUMP (- 10%, p < 0.01), but not in CTRL. BCG linear [Formula: see text] decreased in CTRL (- 50%, p < 0.05), but not in JUMP. The changes in the systolic component of BCG linear iK were correlated to those in stroke volume and V_O2 max (R = 0.44 and 0.47, respectively, p < 0.05). JUMP was less affected by cardiovascular deconditioning, which could be detected by BCG in agreement with standard markers of the cardiovascular condition. This shows the potential of BCG to easily monitor cardiac deconditioning.

Y balance test: Are we doing it right?

OBJECTIVES

The multifaceted characteristic and task-specificity of postural control clearly reflects the need of knowing which factors could influence the balance measures in order to provide reliable and unbiased information. Therefore, this study aimed to investigate the effects of selected anthropometric characteristics, sex, lower limb's strength and dominance on the Y balance test (YBT).

DESIGN

Descriptive laboratory study.

METHODS

Forty-two young adults performed the YBT. The raw and normalized reach distances values were recorded. ANOVA was used to examine differences between sex and limb dominance, whereas multiple linear regression models were built to identify variables associated with better postural control.

RESULTS

No significant sex differences were observed, except for the normalized anterior direction (p=0.0324). No significant differences between limbs emerged. Regression models significantly explained between 8-49% of the variance. Trunk length, strength, and the interaction between sex with strength were the major predictors of the raw measures. Unexpectedly, lower limb length explained only 0.08% of the raw anterior direction variance. Strength and its interaction with sex were positively associated with normalized measures. Surprisingly, the relative lower limb length variable was negatively associated with the normalized measures. Each % point increase in relative lower limb length was associated with a decrease in normalized performance ranging from 1.73 to 4.91%.

CONCLUSIONS

Anthropometric characteristics, sex and lower limb strength differently influenced the YBT measures, regardless of limb dominance. Consequently, these variables should be controlled to limit the variability for an accurate evaluation of postural balance, especially if different YBT measures are used.

Accurate Detection of Dobutamine-induced Haemodynamic Changes by Kino-Cardiography: A Randomised Double-Blind Placebo-Controlled Validation Study

Non-invasive remote detection of cardiac and blood displacements is an important topic in cardiac telemedicine. Here we propose kino-cardiography (KCG), a non-invasive technique based on measurement of body vibrations produced by myocardial contraction and blood flow through the cardiac chambers and major vessels. KCG is based on ballistocardiography and measures 12 degrees-of-freedom (DOF) of body motion. We tested the hypothesis that KCG reliably assesses dobutamine-induced haemodynamic changes in healthy subjects. Using a randomized double-blinded placebo-controlled crossover study design, dobutamine and placebo were infused to 34 volunteers (25 ± 2 years, BMI 22 ± 2 kg/m², 18 females). Baseline recordings were followed by 3 sessions of increasing doses of dobutamine (5, 10, 20 μg/kg.min) or saline solution. During each session, stroke volume (SV) and cardiac output (CO) were determined by echocardiography and followed by a 90 s KCG recording. Measured linear accelerations and angular velocities were used to compute total Kinetic energy (iK) and power (Pmax). KCG sorted dobutamine infusion vs. placebo with 96.9% accuracy. Increases in SV and CO were correlated to iK (r = +0.71 and r = +0.8, respectively, p < 0.0001). Kino-cardiography, with 12-DOF, allows detecting dobutamine-induced haemodynamic changes with a high accuracy and present a major improvement over single axis ballistocardiography or seismocardiography.

Obesity, mechanical and strength relationships to postural control in adolescence

There is preliminary evidence that BMI is positively correlated with movement variability of standing posture. However, this negative effect of obesity on postural control may be mediated by the change in other body scale variables (e.g., mechanical and fitness) that also occur with changes in BMI. This study investigated the influence of selected body scale (height, body mass, BMI), body composition (body fat percentage), mechanical (moment of inertia - MI) and strength (S) variables as predictors of the control of postural motion in adolescents. 125 healthy adolescents (65 boys, 60 girls) with a wide range of BMI (13.8-31.0 kg/m(2)) performed a battery of tests that assessed body composition, anthropometry, muscular strength and postural control. Multiple measures of postural motion variability were derived for analysis with body scale, mechanical and lower extremity strength variables separately for boys and girls. BMI, height and body mass, considered both separately and collectively, were poor and/or inconsistent predictors of variability in all three posture tasks. However, the ratio of lower extremity strength to whole body moment of inertia showed the highest positive correlation to most postural variability measures in both boys and girls and these effects were strongest in the less stable tasks of single leg standing and recovery of stance. Our findings support the hypothesis that diminished lower extremity strength to mechanical constraint ratio compromises the robustness of the strength to body scale relation in movement and postural control.

Design, control, and characterization of a Sliding Linear Investigative Platform for Analyzing Lower Limb Stability (SLIP-FALLS)

A novel device, the Sliding Linear Investigative Platform For Analyzing Lower Limb Stability (SLIP-FALLS), has been designed to study the detection and discrimination thresholds of humans to uniaxial horizontal step, ramp, or sinusoidal translations of the surface upon which they stand or stride. The device also can be used to test the human potential for, and mechanisms of, slips and falls. The SLIP utilizes air bearing technology and a noncontact linear motor to produce ultra-low-vibration translations. The FALLS system measures the forces on four load cells, platform linear and head tri-axial accelerations, four channels of electromyographic data, motor voltage, and a subject's psychophysical response; and derives other physiological and biomechanical measures, like center-of-pressure and shear force. The effect of acceleration and shear force on the accuracy of the center-of-pressure calculations is presented. Operating ranges depend on the interactions among displacement, velocity, acceleration, and jerk parameters for linear translations, and between amplitudes and frequencies for sinusoidal translations. Displacements from 5 microm to 0.277 m, velocities from 5 microm/s to 0.3 m/s, and accelerations up to 2.5 m/s2 are achievable with precise control (i.e., without overshoot), but tradeoffs exist such that all three maxima cannot be reached simultaneously. For a 0.15 m/s linear translation at 4 m/s2, SLIP-FALLS produces substantially less vibration than the worm-driven NeuroTest system. The usefulness of having precise control over movement parameters is discussed.