Clinically meaningful changes in functional performance resulting from self-directed interventions in individuals with arthritis.

OBJECTIVES: To examine the clinical meaningfulness of changes observed in functional performance from two self-directed interventions targeting adults with arthritis. STUDY DESIGN: Randomized controlled trial. METHODS: Participants (n = 312) were randomized to a 12-week self-directed exercise or nutrition intervention. Objective measures of functional performance (6-minute walk, seated reach, grip strength, 30-second chair stand, gait speed, balance) were obtained at baseline, 12 weeks, and nine months. Minimally (≥0.20 standard deviation) and substantially (≥0.50) meaningful changes in functional performance were examined. Changes in the percent 'impaired' and at risk for losing independence using established standards, and associations between physical activity and impairment/risk status were also examined. Group × Time interactions were not significant; therefore groups were combined in all analyses. RESULTS: Minimally (31-71%) and substantially (13-54%) meaningful changes in function were shown. There was a significant decrease in the percentage of participants 'impaired' on the 30-second chair stand (both time points) and gait speed (nine months). The percentage of participants at risk for losing independence significantly decreased for the 30-second chair stand (both time points) and the 6-minute walk (nine months). Those engaging in ≥2 h of leisure-time physical activity were significantly less likely to be impaired on the 6-minute walk, 30-second chair stand, and gait speed at 12 weeks, and the 6-minute walk at nine months. CONCLUSIONS: Interventions that can slow functional declines, and ideally result in clinically meaningful improvements in functional performance among adults with arthritis are needed. Meaningful improvements in various indicators of functional performance can result from self-directed exercise and nutrition programs. These types of programs have the potential for wide-spread dissemination, and thus broad reach.

Gait and postural stability in obese and nonobese prepubertal boys.

OBJECTIVE: To examine differences in gait and postural stability of obese and nonobese prepubertal boys. DESIGN: Percentage of gait cycle in double support was examined to determine significant differences. Postural stability was compared using temporal and frequency measures of the center of pressure in static stance. SETTING: Gait was examined using videography on a 30-meter walkway. Postural stability was examined using a measurement platform. PARTICIPANTS: Ten obese (>95th percentile in body mass index) and 10 nonobese (15th to 90th percentile in body mass index) prepubertal boys aged 8 to 10yrs. INTERVENTION: Participants were examined at three walking cadences as determined by preferred gait cadence. Full vision, darkness, and visually confused conditions were used to accentuate static postural stability differences. MAIN OUTCOME MEASURES: In the presence of dynamic stability differences (gait), static stability measures further investigated stability differences. RESULTS: Obese boys spent significantly (p < .02) greater percentage of gait cycle in dual stance. Obese boys showed significantly (p < .01) greater sway areas, energy, and variability primarily in the medial/lateral direction. CONCLUSIONS: Dual stance differences suggest diminished dynamic stability in obese boys. Greater sway areas in medial/lateral direction in obese boys and the absence of significant frequency measures suggest that the instability observed in obese boys is caused by excess weight rather than underlying postural instability.

Spectral characteristics of postural control in elderly individuals.

OBJECTIVE: To examine the feasibility of using spectral analysis techniques to identify potential biomarkers of diminished postural control in elderly individuals. DESIGN: Data from spectral signatures (derived from postural sway) of 21 young adults and 42 elderly individuals classified as "high" or "low" risk with regard to functional balance capacity were analyzed using Risk Category (3) x Sensory Condition (3) multivariate analyses of variance. Postural control was challenged by varying the visual conditions under which individuals stood on a measurement platform. RESULTS: Results indicated that measures of central tendency and dispersion of the spectral frequency distribution from medial-lateral components of sway (but not antero-posterior sway) clearly differentiated between "high" and "low" risk elderly. Low risk elderly were not different from young adults. High risk elderly exhibited greater dispersion and lower mean frequency than other groups. CONCLUSIONS: Differences in spectral characteristics of medial-lateral components of sway were more related to risk category than to age. Elderly persons with high functional balance capacity displayed characteristics similar to those of young adults. Thus, spectral frequency analysis techniques may be a clinically useful tool for identifying individuals potentially at risk of falling.

Spectral signature of forces to discriminate perturbations in standing posture.

This study proposes a methodology for the collection and analysis of the spectral characteristics of human movement patterns. Specifically, the purpose of this study was to determine the reliability of the spectral signature obtained from postural forces and the usefulness of the technique in identifying perturbations in standing posture. Data collected included trials of the experimental protocol under normal standing conditions and under three experimental conditions designed to perturb stability. Results of this investigation indicated that spectral signatures created from ground forces using the methodology proposed in this study were highly reliable within individuals and across different testing sessions. These data further indicate that spectral signatures obtained from ground reaction forces during standing provide a sensitive indicator of an individual's postural stability.

Effects of seat-surface inclination on postural stability and function of the upper extremities of children with cerebral palsy.

This study investigated the effects of seat-surface inclination on parameters of postural stability and functional use of the upper extremity. 10 non-impaired children and 10 children with cerebral palsy, aged between four and 15 years, were studied. Seat-surface inclinations of 0 degree, 5 degrees anteriorly and 5 degrees posteriorly were used as the experimental conditions. Significant differences were observed on most dependent measures between the two groups. The results suggest that anteriorly tilting the seats of children with cerebral palsy may disturb postural stability, without improving performance of the upper extremity.

Comparative assessment of gait after limb-salvage procedures.

We performed metabolic studies of gait in eighteen patients who had had above-the-knee amputation, block resection and arthrodesis of the knee, or block resection and rotationplasty for a malignant tumor of the distal end of the femur or the proximal end of the tibia. According to the measurement of consumption of oxygen, the patients who had had rotationplasty walked most efficiently. Those who had had arthrodesis used more oxygen and walked at a slower rate.

Interface design for indirect calorimetry in children with cerebral palsy.

The purpose of this study was to design, construct, and validate an alternative subject/instrument interface to collect metabolic data for individuals who, because of impairment, are unable to use a mouthpiece. An industrial designer directed the development of an interface design which would facilitate subject acceptance. A total of 13 subjects (eight children with cerebral palsy and five nonneurologically impaired) participated in the validation study. Metabolic data were collected at rest and during three levels of exercise, using both the traditional mouthpiece and the interface designed for this study. Exercise intensities were matched for both experimental conditions. Subjects exercised using an electrically braked ergometer configured for arm pedaling. A modification in a Beckman Metabolic Cart allowed for the collection of values with a standard mouthpiece and low-flow interface. Validity of the interface was evaluated using a concurrent, criterion procedure. Correlations of mouthpiece vs interface data during rest and across each exercise level for oxygen consumption were high (r = 0.94 to 0.84; p less than 0.05). Similar results were obtained for carbon dioxide production (r = 0.92 to 0.85; p less than 0.05).

Fundamentals of computerised data acquisition in the human performance laboratory.

Researchers of the future will depend upon computer technology to address questions that previously could not be answered using traditional methods of data acquisition. Recent advances in computer design and software availability have eliminated many of the limitations previously associated with computer use in the laboratory setting. Although computerisation facilitates the acquisition of laboratory data, identification of errors introduced into the measurement is often more difficult. The laboratory computer is only one component of an automated data acquisition system. A system designed to collect physiological data comprises several primary components, including: (a) sensing element; (b) signal amplification/conditioning circuits; (c) analogue display; (d) computer interface; (e) laboratory computer; and (f) acquisition software. The acquisition and conditioning of analogue signals is accomplished using traditional laboratory procedures familiar to the researcher. Converting this analogue signal into a digital format used by the computer, however, represents new techniques. Fundamentals of computerised data acquisition are discussed. An understanding of how an automated data acquisition system is configured and the techniques used to transform the values will assist the user in identifying sources of error introduced into the measurement. Additionally, familiarization with the methods of computerisation will provide insight into future applications of computer technology in the human performance laboratory.

Design and validation of an automated hydrostatic weighing system.

The purpose of this study was to design and evaluate the validity of an automated technique to assess body density using a computerized hydrostatic weighing system. An existing hydrostatic tank was modified and interfaced with a microcomputer equipped with an analog-to-digital converter. Software was designed to input variables, control the collection of data, calculate selected measurements, and provide a summary of the results of each session. Validity of the data obtained utilizing the automated hydrostatic weighing system was estimated by: evaluating the reliability of the transducer/computer interface to measure objects of known underwater weight; comparing the data against a criterion measure; and determining inter-session subject reliability. Values obtained from the automated system were found to be highly correlated with known underwater weights (r = 0.99, SEE = 0.0060 kg). Data concurrently obtained utilizing the automated system and a manual chart recorder were also found to be highly correlated (r = 0.99, SEE = 0.0606 kg). Inter-session subject reliability was determined utilizing data collected on subjects (N = 16) tested on two occasions approximately 24 h apart. Correlations revealed high relationships between measures of underwater weight (r = 0.99, SEE = 0.1399 kg) and body density (r = 0.98, SEE = 0.00244 g X cm-1). Results indicate that a computerized hydrostatic weighing system is a valid and reliable method for determining underwater weight.

Duration of muscle activity during standing in normally and slowly developing children.

Research in motor control indicates that there are fixed patterns of activity which occur in certain muscle groups involved in standing in adults. The purpose of this study was to assess patterns of duration of muscle activity during quiet standing with and without superimposed arm movement in young children with normal and delayed motor development. Thirty-three children 4, 6, 8 and 10 years of age were screened for level of motor development and classified as either normally or slowly developing. Children performed two tasks: standing and standing with a superimposed 90 degree shoulder abduction movement. Using surface electrodes, EMG activity was monitored in Gastrocnemius, Tibialis Anterior and Erector Spinae muscle groups. The percentage of time activity was present in individual muscle groups was analyzed as a function of age and developmental level. Results indicated that quiet standing in children with delayed motor development was characterized by greater duration of activity in trunk than in leg muscles while in normal children, there was a more equal distribution of muscle activity between the legs and trunk. Both groups of children accommodated superimposed arm movement by increasing the percentage of time Erector Spinae activity was present. Patterns of duration of muscle activity in the legs were, however, different for the two groups of children.