The goal of this study was to examine the effects of 3 factors and their interactions on posturography: a period of time to become accustomed to the force platform before the initiation of data collection, presence of a visual fixation point, and participant talking during testing. The postural stability of 30 young adults and 30 older adults was evaluated to determine whether any observed effects were confounded with age. Analysis of variance techniques were used to test all possible combinations of the 3 factors. We hypothesized that all 3 factors would significantly affect postural stability. For both participant groups, the results suggest that a period of time to become accustomed to the force platform before the initiation of data collection and a visual fixation point significantly affect postural control measures, while brief participant talking does not. Despite this, no significant interactions existed suggesting that the effects of these factors, which may occur in clinical testing, do not depend on each other. Our results suggest that inconsistencies in posturography testing methods have the potential to significantly affect the results of posturography, underscoring the importance of developing a standardized testing methodology.
Melissa R. Taylor, Erin E. Sutton, Wiebke S. Diestelkamp and Kimberly Edginton Bigelow
Bruce Elliott, J. Robert Grove and Barry Gibson
Eight international baseball pitchers were filmed in a laboratory while throwing from a pitching rubber attached to a Kistler force platform. Following a warm-up, all subjects threw fastballs (FB) until two strike pitches were assessed by an umpire positioned behind the catcher for both wind-up and set pitching techniques. Subjects then followed the same procedures for curveball pitches (CB). Both vertical (Z) and horizontal (Y) ground reaction force (GRF) data were recorded. A shutter correlation pulse was encoded so the temporal data from the film could be synchronized with the kinetic data from the force platform. Analysis of variance was used to analyze differences in force data at selected points in both pitching actions for both techniques. Vertical and horizontal GRFs increased from the first balance position to maximum levels at the cocked position for both techniques. Nonsignificant changes in GRF then occurred between the cocked position and front-foot landing. The Z GRFs were similar throughout the pitching action but higher in magnitude for the CB compared to the FB. Mean resultant forces were similar for the three fastest FB pitchers when compared to the three slowest pitchers. However, the slower group produced their peak resultant force earlier in the action, thus reducing the ability to drive over a stabilized front leg.
Michael J. Duncan, Joanne Hankey and Alan M. Nevill
This study examined the efficacy of peak-power estimation equations in children using force platform data and determined whether allometric modeling offers a sounder alternative to estimating peak power in pediatric samples. Ninety one boys and girls aged 12–16 years performed 3 countermovement jumps (CMJ) on a force platform. Estimated peak power (PPest) was determined using the Harman et al., Sayers SJ, Sayers CMJ, and Canavan and Vescovi equations. All 4 equations were associated with actual peak power (r = 0.893−0.909, all p < .01). There were significant differences between PPest using the Harman et al., Sayers SJ, and Sayers CMJ equations (p < .05) and actual peak power (PPactual). ANCOVA also indicated sex and age effect for PPactual (p < .01). Following a random two-thirds to one-third split of participants, an additive linear model (p = .0001) predicted PPactual (adjusted R 2 = .866) from body mass and CMJ height in the two-thirds split (n = 60). An allometric model using CMJ height, body mass, and age was then developed with this sample, which predicted 88.8% of the variance in PPactual (p < .0001, adjusted R 2 = .888). The regression equations were cross-validated using the one-third split sample (n = 31), evidencing a significant positive relationship (r = .910, p = .001) and no significant difference (p = .151) between PPactual and PPest using this equation. The allometric and linear models determined from this study provide accurate models to estimate peak power in children.
Catherine A. Stevermer and Jason C. Gillette
Variation in the timing indicators separating sit-to-stand (STS) into movement phases complicates both research comparisons and clinical applications. The purpose of this study was to use kinetic reference standards to identify accurate kinematic and kinetic indicators for STS movement analysis such that consistent indicators might be used for STS from varied initial postures. Healthy adults performed STS using 4 foot placements: foot-neutral, foot-back, right-staggered, and left-staggered. Kinetic and kinematic data were collected from force platforms and an 8-camera video system. Initiation, seat-off, vertical posture, and termination were detected with 5% start and 7.5% end thresholds for changes in kinetic and kinematic STS indicators. Timing differences between kinetic and kinematic indicator time points and the reference vertical seated reaction force end point (seatoff) were determined. Kinematic indicators were compared with selected kinetic indicators using timing differences, statistical similarity, and internal consistency measures. Our results suggest that a single force platform system measuring vertical GRF or a simple camera system to evaluate the shoulder marker position and velocity can accurately and consistently detect STS initiation, seat-off, and vertical posture. In addition, these suggested STS indicators for initiation, seat-off, and vertical posture were not dependent upon foot placement.
Valentina Agostini, Emma Chiaramello and Marco Knaflitz
Static posturography provides an objective assessment of postural control by characterizing the body sway during upright standing. The center of pressure (COP) signal is recorded by a force platform, and it is analyzed by means of many different models and techniques. Most of the parameters calculated according to these different approaches are affected by relevant intra- and intersubject variability or do not have a clear physiological interpretation. Traditional approaches decompose the COP signal into anteroposterior and mediolateral time series, corresponding to ankle plantar/dorsiflexion and hip adduction/abduction, respectively. In this study we hypothesized that COP signals show inherent rotational characteristics. To verify our hypothesis we applied the rotary spectra analysis to the two-dimensional COP signal to decompose it into clockwise and counterclockwise rotational components. We demonstrated the presence of rotational components in the COP signal of healthy subjects, providing a reference data set of the spectral characteristics of these components.
Zheng Wang, Peter C. M. Molenaar and Karl M. Newell
The experiment was set up to investigate the inter- and intrafoot coordination dynamics of postural control on balance boards. A frequency domain principal component analysis (PCA) was applied on 4 center of pressure (COP) time series collected from two force platforms to reveal their contributions to postural stability. The orientation of support played a more significant role than its width in channeling the foot coordination dynamics. When the support was oriented along the AP-challenging direction, the 4 COPs revealed a parallel contribution to the 1st principal component (PC1) indicating an interdependence of the foot coordination in both directions. When the support was positioned along the ML-challenging direction, the COPs in the AP direction showed larger weightings to PC1 implying an interfoot coordination. These findings provide evidence that COP coordination operates in adaptive ways to sustain postural stability in light of changing support constraints to standing.
Semyon M. Slobounov, Robert Simon, Wayne Sebastianelli, Angela Carlson and William E. Buckley
A variety of assessment devices have been developed for scientific investigation on human movement that can also be used to assess the progress of a rehabilitation program. The present investigation was undertaken to show how this technology can be combined with the most aggressive type of medical intervention and rehabilitation. Advanced technology was used to assess the physical rehabilitation parameters of active range of motion (AROM) and sport-specific functional progression for an Olympic-caliber diver who had bilateral wrist problems. AROM was measured for both wrists using a Flock of Birds motion-tracking device, and functional progression was assessed with an Advanced Mechanical Technology Inc. force platform for measuring the center of pressure (CP) area. The results of the treatment were clinically favorable, with an increase in AROM and a decrease in the CP area for functional motor control. The technology provided useful information about the progress of a rehabilitation program.
Dawne Larkin and Helen E. Parker
This study investigated landing patterns of children aged 7–9 years with either developmental coordination disorder (DCD) or without coordination problems (NC). Initially, 16 DCD and 15 NC children were videotaped performing two-foot landings from a height of 21.5 cm onto a force platform sampling at 500 Hz. Each landing was videotaped at 60 Hz. Regression modeling of the data identified that 72% of peak maximum loading force was explained by landing time, knee angle at touchdown, and hip joint range of motion. Dis-criminant function analysis using landing force, landing time and lower limb joint kinematic variables reliably separated the groups. In the second part, 12 DCD and 10 NC children participated in 6 weekly landing lessons. The only significant adjustment produced by the program was a decrease in the range of motion at the hip in response to instructions to look straight ahead and sit into the landing.
Adrienne J. McNamara, Michael J. Pavol and Katherine B. Gunter
Community-based exercise programs are popular for achieving physical activity among older adults, but the amount of physical activity obtained through such programs is unknown. This study quantified the bone-loading forces and levels of cardiovascular activity associated with participation in “Better Bones and Balance” (BBB), a community-based fall- and fracture-prevention program for older adults.
Thirty-six postmenopausal women age 73.2 ± 7.6 yr engages in BBB participated in this study. Ground-reaction forces (GRFs) associated with BBB exercises were evaluated using a force platform. Session and weekly totals of minutes of moderate to vigorous physical activity (MVPA) and total time spent above 55% maximum heart rate (HR) were measured using accelerometers and HR monitors, respectively.
BBB exercises produced mean 1-leg GRFs of 1.4–2.2 units body weight. Weekly BBB participation was associated with 126 ± 31 min of MVPA.
Activity obtained by BBB participation meets recommended guidelines for skeletal and cardiovascular health.
Telassin Silva Homem, Fernando Silva Guimarães, Maurício Santos Soares, Leandro Kasuki, Mônica Roberto Gadelha and Agnaldo José Lopes
Advances in the knowledge of acromegaly are leading to an increase in the survival rate of acromegalic subjects. This study was conducted to evaluate balance control, risk of falls, and peripheral muscle function in acromegalic older adults. Seventeen older subjects with acromegaly (67 [63–73] years) and 20 paired control subjects were evaluated with balance scales, force platform, and knee isokinetic dynamometry tests. There were significant differences between the groups on several balance and gait scales, with a worse performance and greater risk of falls in the acromegalic older adults. Acromegalic older adults had lower values for peak torque, maximum repetition of the total work, and total work during extension at 240°/s. The acromegalic older adults had higher values in the medial-lateral range. Acromegaly subjects had lateral instability that compromises their body balance and increases the risk of falls. Moreover, there was a propensity for muscle fatigue in these individuals.