Biomedical subjects

Tammy M Owings

Publications and source records attributed to Tammy M Owings.

10 recordsLinked to original sources

PubMed2006

Nonsurgical strategies for healing and preventing recurrence of diabetic foot ulcers.

We have outlined an approach to the nonsurgical treatment of diabetic foot ulcers based on an understanding of their etiology. We have emphasized the importance of off-loading as the crucial element to success in healing foot ulcers and preventing their recurrence in those with diabetes. Computerized design of custom insoles can allow the unloading of elevated plantar pressure while incorporating the shape of the foot, which was formerly the major criterion used insole design.

Biomechanical Phenomena↗

PubMed2005

Lower extremity strength plays only a small role in determining the maximum recoverable lean angle in older adults.

BACKGROUND: The purpose of this study was to determine the extent to which measures of lower extremity strength and power contribute to the ability of older men and women to restore postural equilibrium using a single-step recovery following a large postural disturbance. METHODS: The postural disturbance, which has been used as a surrogate for forward-directed falls, involved a sudden release from a forward-leaning angle. The ability to recover using a single step was evaluated as the maximum recoverable lean angle for 56 healthy older women and men. Maximum voluntary isometric and isokinetic strength was measured for ankle plantarflexion and dorsiflexion, knee flexion and extension, and hip flexion and extension. Discriminant analysis was used to determine the strength measures that best classified participants as members of the highest (n = 14) or lowest (n = 14) quartiles of maximum recoverable lean angle. Those variables were subsequently entered into a regression analysis to characterize the relationship between strength and maximum recoverable lean angle for the entire participant sample. RESULTS: Maximum isokinetic dorsiflexion strength at 90 degrees /s satisfied the criteria of the stepwise discriminant analysis, and correctly classified 82.1% of the participants in the highest or lowest quartiles of maximum recoverable lean angle. The multiple regression procedure, performed on all participants (n = 56) revealed a significant quadratic relationship between maximum isokinetic dorsiflexion strength at 90 degrees /s and maximum recoverable lean angle (R2 = 0.295; p <.001). CONCLUSIONS: Lower extremity strength makes a small, but significant contribution to maximum recoverable lean angle. However, because 70% of the shared variability remained unaccounted for, it is suggested that other performance factors, such as coordination, may be of greater importance to performance of this time-critical motor task.

Accidental Falls↗

PubMed2004

Step width variability, but not step length variability or step time variability, discriminates gait of healthy young and older adults during treadmill locomotion.

The variability of spatial and temporal step kinematics have separately been shown to prospectively predict falls by older adults. However, the published literature has not addressed the relative importance of the information related to locomotion control contributed by variability of spatial variables, temporal variables, or both. We conducted a post hoc analysis to determine the extent to which the variability of spatial and temporal step kinematics are independent descriptors of locomotion control in healthy young and older adults. A second purpose of the analysis was to establish the extent to which treadmill walking mimics overground walking using a benchmark for step kinematics. Eighteen young adults and 12 older adults walked at a self-selected velocity on an instrumented treadmill from which step length variability, step width variability and step time variability were computed. Stepwise discriminant analysis correctly classified group membership of 70 percent of the 30 subjects (i.e., young or older adult) using only step width variability (p=0.037, Wilk's lamda=0.854). Step width variability was 70+/-57 percent larger than step length variability (p<0.001). This relationship was similar to that of the benchmark established for overground locomotion. The results suggest that for healthy younger and older adults step width variability is a more meaningful descriptor of locomotion control than step length variability and step time variability. Given the potential clinical impact, further systematic study and improvement of the methods and technology for acquiring step kinematic data are warranted.

Adult↗

PubMed2004

Variability of step kinematics in young and older adults.

Fall-related injuries are the most common and serious medical problems facing older adults. Recent studies of older adults have focused on the variability of step kinematics and the relationship to falling. The accuracy of step variability estimates is proportional to the number of steps that are collected. The use of an instrumented treadmill allows simultaneous collection of spatial and temporal step kinematics for a large number of continuous steps. The current study was conducted to determine the influence of age, walking velocity and handrail use on the variability of step kinematics using a treadmill protocol. Eighteen young adults (average age: 27.7 +/- 3.3 years) and 12 healthy older adults (average age: 73.4 +/- 2.3 years) were recruited from the community. Temporal and spatial gait parameters were quantified using custom designed software from measurements collected during treadmill walking. The primary independent variables were the variability of step length, step width, and step time. Step width variability of older adults was significantly larger than that of young adults. Walking velocity did not influence step kinematic variability. Handrail usage influenced the variability of step length and step width, but not of step time. The present results, and those of previous studies, point to a consistent relationship between age and step width variability. Since step width variability has been implicated in falls, further research is warranted.

Adult↗

PubMed2003

Measuring step kinematic variability on an instrumented treadmill: how many steps are enough?

Variability of step kinematics has been associated with falls by older adults. However, between-study differences with regard to the number of steps used to compute variability have varied by an order of magnitude. If the number of steps used to compute variability is too low there is the potential for a statistically spurious outcome. On the other hand, for subjects with mobility impairments a protocol requiring too many steps to estimate variability imposes an unnecessary burden on the subjects. We have determined the minimum number of steps needed to estimate the variability of spatial and temporal step kinematics. More than 700 steps were collected during level walking on an instrumented treadmill. Accurate estimation of step kinematic variability required at least 400 steps. The increased error in estimating the mean and standard deviations of the step kinematic variables with too few steps can impose an experimental cost with regard to statistical design considerations. The extent to which translation of these results can be made to the variability of spatial and temporal step kinematics collected during over-ground walking awaits further research.

Adult↗

PubMed2003

Influence of ball velocity, attention, and age on response time for a simulated catch.

PURPOSE: The ability of a baseball infielder to respond to a batted ball may provide the best defense for avoiding injury. This study investigated the response times of young athletes performing a simulated baseball-fielding task to estimate the maximum velocity with which a baseball can leave the bat and allow a player, standing 13.7 m away, to safely respond to the approaching ball. METHODS: Fifty boys and 50 girls between the ages of 8 and 16 yr participated. Baseballs were projected at the subjects who were standing in a standardized position behind a safety net. Two components of response time, reaction time and movement time, were determined using a motion capture system. The influences of baseball velocity (26.8 and 33.5 m.s(-1) and level of attention (full attention and attention splitting) on response time for a simulated baseball-fielding task were characterized. Based on the response times for each age group, the maximum exit-velocity from a baseball-bat interaction that would allow a young baseball player sufficient time to safely respond to an approaching baseball was calculated. RESULTS: The results showed that subjects had sufficient time to respond to exit-velocities from 26.8 m.s-1 (8- to 9-yr-old group) to 33.5 m.s-1 (16-yr-old group). However, the accuracy of the response was negatively affected by baseball velocity. CONCLUSIONS: If the exit-velocities seen during actual competition exceed the calculated maximum exit-velocities for these age groups, then our preliminary data suggest that modifications to the game of baseball that would reduce the actual exit-velocities and serve as an effective means to reduce the potential for serious or catastrophic injury are warranted.

Adolescent↗

PubMed2002

Body segment inertial parameter estimation for the general population of older adults.

The practical determination of accurate body segment inertial parameters for the general older adult population remains a problem, especially in estimating these parameters for women and accounting for variations in body type. A method is presented for determining the mass and center of mass location of the body segments of individuals within the general population of older adults. Effects of sex and body type on older adult mass distribution are accounted for using 32 easily obtainable body measurements. The method is based on existing results from different data sources and employs a combination of validated estimation approaches, including: body mass and segment length proportions, linear and nonlinear regression equations, and a mathematical model of the trunk. The method was applied to a validation sample of healthy, community-dwelling older adults (29 men, 50 women). Predicted body mass was 96.7+/-4.8% and 95.7+/-3.7% of measured body mass in the men and women, respectively. The estimates of body segment mass and trunk center of mass location for the sample population approximate those reported in the literature, supporting the validity of the described method. By producing practical, subject-specific estimates of body segment inertial parameters, the method should allow more accurate biomechanical analyses of the older adult population.

Age Factors↗

PubMed2002

Influence of lower extremity strength of healthy older adults on the outcome of an induced trip.

OBJECTIVES: To determine whether decreased lower extremity strength contributes to trip-related falls in older adults. DESIGN: A cross-sectional sample of older adults were safety-harnessed and tripped while walking using a concealed, mechanical obstacle. Lower extremity strength was compared between trip outcome groups. SETTING: A biomechanics research laboratory. PARTICIPANTS: Seventy-nine healthy, community-dwelling adults aged 65 and older (50 women). MEASUREMENTS: Ankle, knee, and hip flexion and extension strength were measured isometrically and isokinetically. Measured strengths were subjected to a factor analysis. Strength factor scores were compared between those who recovered from the trip and those who fell by three previously identified mechanisms: during-step, after-step, and elevating-response falls. RESULTS: Seven common factors, one associated with each direction of exertion at each joint and one with the time rate of moment increase, explained 88% of the variance in measured strength. The during-step (n=5) fallers were significantly stronger in the ankle extension (plantarflexion), knee flexion, overall extension, and total strength factors than those who successfully recovered using a similar, lowering strategy (n=26). The elevating-response faller (n=1) was stronger in the plantarflexion and overall extension factors than most of those who recovered using a similar, elevating strategy (n=11). Two of three after-step fallers were among the weakest subjects tested. CONCLUSION: Weak older adults and the strongest older adults may be at greater risk of falling from a trip, although by different mechanisms. High strength may increase the likelihood of a during-step or elevating-response fall; decreased strength may increase the likelihood of an after-step fall.

Accidental Falls↗

PubMed2002

Can fall-related hip fractures be prevented by characterizing the biomechanical mechanisms of failed recovery?

Unintentional injuries are the seventh leading cause of death in adults ages 65 and older, and the greatest number of these deaths results from fall-related injuries. In addition to the startling mortality, the morbidity associated with fall-related injuries, particularly hip fractures, has become a research imperative. This article reviews a series of studies that was undertaken to determine the biomechanical reasons that older adults are unable to recover from very large postural perturbations that are applied during locomotion that, if not corrected, can lead to a fall. Our protocol involves causing older adults to trip unexpectedly while walking normally in the laboratory. The results from this series of experiments were used to design an experiment that characterized the biomechanical similarities between recovery biomechanics after an induced trip and those following a large postural perturbation delivered by a motorized treadmill. Collectively, we have been able to document different recovery strategies and categories of falls by older adults following an induced trip; the biomechanical causes of these falls by older adults; and the very rapid motor adaptations that occur with repeated exposure to large perturbations that may be protective against falls from tripping and, therefore, reduce the substantial fall-related morbidity and mortality in older adults.

Accidental Falls↗

PubMedDate not supplied

Motor control of the vastus medialis oblique and vastus lateralis muscles is disrupted during eccentric contractions in subjects with patellofemoral pain.

BACKGROUND: Inappropriate control of the vastus medialis oblique and vastus lateralis muscles by the central nervous system can contribute to maltracking of the patella. HYPOTHESIS: The activation timing and amplitude of the vastus medialis oblique and vastus lateralis muscles will be different between normal subjects and patients with patellofemoral pain. STUDY DESIGN: Controlled laboratory study. METHODS: Subjects with patellofemoral pain and asymptomatic control subjects performed maximum voluntary knee extension contractions initiated from a flexed and an extended position. The activation timing and amplitude of the vastus lateralis and vastus medialis oblique muscles were quantified from the recorded electromyographic signals. RESULTS: There were no between-group differences in activation timing. The activation amplitude of the vastus medialis oblique and vastus lateralis muscles of the patellofemoral pain subjects was altered to the greatest extent during eccentric contractions and differed significantly from that of control subjects. CONCLUSIONS: The activation amplitudes of the vastus medialis oblique and vastus lateralis muscles of subjects with patellofemoral pain are consistent with a laterally tracking patella during eccentric contractions. CLINICAL RELEVANCE: The findings suggest the clinical importance of determining whether altered activation patterns are sensitive to rehabilitation, and, if so, if subjective reports of knee joint pain and function parallel changes in the activation patterns as a result of rehabilitation.

Adult↗