The effect of exhausting aerobic exercise on the timing of anticipatory postural adjustments.

AIM: The aim of the study was to investigate the influence of exhausting aerobic exercise on the timing of anticipatory postural adjustments (APAs). METHODS: The APAs of 12 participants were recorded at baseline, after a .VO2max running test, and again following a 45-min rest period. APAs were induced using a rapid bilateral arm-raising maneuver, and were analyzed in the rectus abdominis, hamstring group, gluteal group, and lumbar and thoracic paraspinal muscles using electromyography. Postural stability was assessed by monitoring anterior/posterior displacement of the center of pressure using a force plate. We hypothesized that APA onset would be ear lier following exhausting aerobic exercise as compared to the baseline measures, but that this effect would be transient (i.e., APA onset following the rest period would not differ from that at baseline). RESULTS: Exhausting aerobic exercise resulted in a significantly earlier APA in one of the 5 muscles evaluated, the thoracic paraspinal group, and this effect persisted 45-min postexercise. Exhausting aerobic exercise did not affect postural stability during the rapid arm-raising maneuver. CONCLUSION: The findings lend tentative support for the notion that earlier APAs constitute a functional adaptation by the motor system to maintain postural stability in the presence of fatigue.

Stepping performance during obstacle clearance in women: age differences and the association with lower extremity strength in older women.

OBJECTIVE: To compare stepping performance during obstacle clearance in younger and older women, and to examine the relationship between lower extremity strength and stepping performance during obstacle clearance in older women. DESIGN: Correlational study. SETTING: A small community. PARTICIPANTS: Twenty-four older women (mean age = 74.4), and 16 younger women (mean age = 20.7). The older participants lived independently in the community and were able to walk unaided. MEASUREMENTS: Lower extremity muscle strength, measures of stepping performance including reaction time, movement time, extent of obstacle clearance, time to clear obstacle, among others. MAIN RESULTS: The older women were far slower in stepping than the younger women. Toe trajectories differed between older and younger women during the initial portion of the step. The younger women tended to lift the toe straight up, whereas the older women tended to move the toe backward, away from the obstacle, passing farther from the obstacle when the toe cleared the obstacle height. There was little, if any, association between relative lower extremity strength and stepping performance during obstacle clearance in older women. CONCLUSIONS: Dramatic differences in the speed of volitional stepping performance were found between younger and older women. Among the older women, lower extremity strength was not related to volitional stepping performance.

Effect of the intensity of wireless telephone conversations on reaction time in a braking response.

Recently, concern has grown about the extent to which wireless telephone use by motor vehicle drivers constitutes a threat to traffic safety. This experiment investigated the effect of the intensity of wireless telephone conversations on reaction time (RT) for a braking response. Using a laboratory station to mimic the foot activity in driving, 16 adults were instructed to release the accelerator pedal and depress the brake pedal as quickly as possible following the activation of a red brake light. Mean RT was measured for 5 conditions which manipulated the intensity of a conversation, i.e., demand for attention, conducted on a wireless telephone. Analysis indicated that wireless telephone use caused a decrement in RT, however, there was no significant effect associated with intensity of the conversation across intensity.

Circumstances and consequences of falls in independent community-dwelling older adults.

BACKGROUND: knowledge of the circumstances and consequences of falls in older adults is important for understanding the aetiology of falls as well as for effective clinical assessment and design of fall prevention strategies. Such data, however, are relatively scarce, especially in community-dwelling elders. METHOD: accidental falls (including their circumstances and consequences) occurring in 96 male and female participants between 60 and 88 years of age were monitored prospectively for 1 year. After the monitoring period, participants were divided into three groups based on fall status: non-fallers (n = 46), one-time fallers (n = 27) and recurrent fallers (n = 23). Frequency distributions were created for selected circumstances and consequences of falls and the prevalence of these consequences were examined. RESULTS: 50 participants (52%) fell during the 1 year period, amassing 91 falls. Trips and slips were the most prevalent causes of falls, accounting for 59% of falls. Falls most often occurred during the afternoon and while subjects walked on level or uneven surfaces. Fallers most commonly attributed falls to hurrying too much. Fractures resulted from five of the 91 falls and eight other falls resulted in soft tissue injuries that required treatment by a physician. There were no differences between one-time and recurrent fallers in the circumstances and consequences of falls. However, several notable differences were found between men (n = 20) and women (n = 30) who fell. Falls by men most often resulted from slips whereas falls by women most often resulted from trips. Moreover, women and men differed in the time of the year in which falls occurred, with men falling most often during winter and women during summer. CONCLUSIONS: the results of this study provide insight into the circumstances and consequences of falls among independent community-dwelling older adults and suggest some possible ways of preventing falls. Preventive services, however, should not solely target recurrent fallers, nor should the type of services necessarily differ for one-time and recurrent fallers.

Correlates of recurrent falling in independent community-dwelling older adults.

This study compared the ability of selected measures of vision, health, physical activity and performance, and fall history to predict the risk of recurrent falls in independent community-dwelling older adults. Of particular interest was the association between visual field (VF) constriction and falling. Age-related VF constriction is well documented and is known to accelerate in persons over age 55. Although several authors have implied that VF constriction in older adults could contribute to instability and falls, there has been no attempt to systematically examine this relationship. A battery of tests were administered to men and women (N = 96) 60-88 years of age. Falls were closely monitored for 1 year following the testing. Fifty of the 96 participants (52%) fell during the 1-year monitoring period, amassing a total of 91 falls, 5 of which resulted in fractures. There were 46 nonfallers, 27 one-time fallers, and 23 recurrent fallers. A stepwise logistic regression analysis revealed that average VF constriction, use of eyeglasses, and low systolic blood pressure were independently associated with recurrent falling. On discriminant function analysis, these 3 variables predicted status as a recurrent faller correctly in 48% of cases, and predicted nonfaller status correctly in 93% of cases. The overall performance of the model was 70%. Hypotheses are offered for how average VF constriction, use of eyeglasses, and low systolic blood pressure could influence stability and fall risk in older adults.

Size of the visual field in collegiate fast-pitch softball players and nonathletes.

The purpose of this study was to examine whether visual-field size differed between female Division I collegiate fast-pitch softball players and female college students who were nonathletes. The relationship between visual-field size and batting performance among the softball players was also examined. 24 female undergraduate students (12 varsity fast-pitch softball players and 12 nonathletes) participated. The size of the visual field was measured via manual kinetic perimetry, and batting performance was assessed using a batting-skill test as well as batting averages for an entire competitive season. Analyses indicated that the mean visual-field size of softball players was significantly larger than that of nonathletes. However, there was no relationship between visual-field size and batting performance among the softball players. Results are discussed with respect to the origin of the superiority of visual-field size of softball players.

Visual regulation of gait in bipedal locomotion: revisiting Lee, Lishman, and Thomson (1982).

This study expanded the database regarding the visual regulation of gait in the long jump approach (LJA) in the direction of novice long jumpers. It showed that the pattern of visual influence on gait adjustments was similar for novices and experts. This was taken to indicate that visual regulation of gait in the LJA is not a specially trained skill as much as it is a natural means of controlling gait. The study also showed that novices' step lengths were regulated principally by modifying vertical impulse. This finding replicated that of an influential study by D. N. Lee, J. R. Lishman, and J. A. Thomson (1982). Results are discussed with respect to the prevailing ecological notion that the optical variable tau provides principal informational support for regulation of gait in the LJA.