Biomedical subjects

V S Mercer

Publications and source records attributed to V S Mercer.

3 recordsLinked to original sources

PubMed2000

Effects of footwear on measurements of balance and gait in women between the ages of 65 and 93 years.

BACKGROUND AND PURPOSE: Footwear is not consistently standardized in the administration of the Functional Reach Test (FRT), Timed Up & Go Test (TUG), and 10-Meter Walk Test (TMW). This study was conducted to determine whether footwear affected performance on these tests in older women. SUBJECTS: Thirty-five women, aged 65 to 93 years, were recruited from assisted living facilities and retirement communities. METHODS: Each subject performed the FRT, TUG, and TMW wearing walking shoes, wearing dress shoes, and barefooted. Because of space constraints at the facilities where the testing was performed, 22 subjects performed the FRT and TUG on a linoleum floor and 13 subjects performed the tests on a firm, low-pile, carpeted floor. All 35 subjects completed the TMW on a firm, low-pile, carpeted floor. One-way repeated-measures analyses of variance (ANOVAs) and a Tukey Honestly Significant Difference test were used to compare the outcomes for the 3 footwear conditions, with separate ANOVAs conducted for the different floor surfaces for the FRT and TUG. RESULTS: Subjects performed better on the FRT when barefooted or wearing walking shoes compared with when they wore dress shoes, regardless of floor surface. Differences were found among all footwear conditions for the TUG performed on the linoleum floor and for the TMW. For these tests, the women moved fastest in walking shoes, slower barefooted, and slowest wearing dress shoes. CONCLUSION AND DISCUSSION: Footwear should be documented and should remain constant from one test occasion to another when the FRT, TUG, and TMW are used in the clinic and in research. Footwear intervention may improve performance of balance and gait tasks in older women.

Aged↗

PubMed1999

Postural synergies associated with a stepping task.

BACKGROUND AND PURPOSE: Synergistic relationships among multiple muscle components are thought to exist to simplify control of posture and movement. The purpose of this study was to examine the extent to which children, young adults, and older adults exhibit consistent sequences of postural muscle activation when lifting the right foot onto a step from a standing position. SUBJECTS: Twenty subjects without known impairments of the neuromuscular system (10 male, 10 female) in each of 3 age groups--children (8-12 years), young adults (25-35 years), and older adults (65-73 years)--participated. METHODS: A pressure switch taped to the subject's right foot was used to determine movement onset and offset. Latencies of muscle activation were determined using surface electromyography. A preferred postural synergy was defined as the sequence of postural muscle activation observed during the majority of trials for each subject. RESULTS: Mean movement times did not differ among age groups. Although the left tibialis anterior (TA) muscle was the first of the postural muscles activated in 93% of the trials, subjects displayed considerable variability in the subsequent order of postural muscle activation. Across subjects, a total of 14 different preferred postural synergies were observed. Age groups did not differ in the number of different synergies. CONCLUSION AND DISCUSSION: Early TA activation may reflect biomechanical constraints of the stepping task, producing forward displacement of the center of mass over the changing base of support. The fact that subjects of all ages were quite variable in the specific sequences of muscles activated subsequent to the TA suggests that, for this type of task, therapists should not focus their interventions on facilitating execution of particular synergy patterns.

Adolescent↗

PubMed1997

Age Group Differences in Postural Adjustments Associated With a Stepping Task.

In this study, differences among age groups in the postural adjustments associated with a stepping task were identified. Twenty subjects from each of 3 age groups, children (8-12 years), young adults (25-35 years), and older adults (65-73 years), performed the task in 2 movement contexts: place and step. In place, the subject simply lifted the foot and placed it on the step. In step, the subject lifted the foot, placed it on the step, and stepped up onto the step. Latencies of postural and focal muscle activation were determined by using surface electromyography and pressure switches. Center of pressure (CP) data were obtained by using a force platform. Subjects in all 3 age groups consistently demonstrated postural adjustments before movement initiation. Children displayed longer postural latencies than young adults as well as disproportionately large values for CP path length. Older adults showed prolonged postural-focal latencies and decreased CP excursions compared with the 2 younger age groups. These results suggest that maturation of coordination between posture and movement may not be fully complete in 8- to 12-year-olds and that increased restraint characterizes the performance of postural adjustments in healthy persons over 65 years of age.

center of pressure↗