Biomedical subjects

E Waked

Publications and source records attributed to E Waked.

9 recordsLinked to original sources

PubMed1998

Improving balance.

OBJECTIVE: To test the hypothesis that shoes made with a sole material that retains compressed thickness between steps (low resiliency) provide balance better than and comfort equal to shoes composed of high resiliency sole material. SETTING: Older subjects were recruited from a medical clinic population, and younger subjects came from a recreational sports population. DESIGN: A randomized-order, cross-over, controlled comparison design. PARTICIPANTS: Groups comprised random samples of 30 older (mean age 66 years, SD+/-3.0), and 30 younger (mean age 34 years, SD+/-6.0) healthy men who met age selection criteria. MEASUREMENTS: Stability was inferred by sway measures: sway velocity (cm x s(-1)), X-Y area (cm2), and radial area (cm2). Comfort was measured by direct scaling and magnitude estimation using an 11-point ratio scale. RESULTS: Stability inferred by sway velocity was 311% (P < .001) and 31% (P < .001) poorer for younger and older groups, respectively, for high and low resiliency interfaces. Sway velocity with low resiliency interface was lower than bare platform, the lowest ever recorded under equivalent conditions (P < .001). All interfaces were equally comfortable. CONCLUSIONS: Stability rises with low resiliency interfaces and declines with high resiliency interfaces: sway velocity in older people wearing hard-soled footwear incorporating low resiliency technology would be 20% lower than in younger people wearing most current athletic and walking shoes. Inasmuch as existing theory can not account for improved balance with interfaces, we propose that when humans are supported by rigid support surfaces, elastic biologic tissues store energy from postural adjustments and locomotion, which is returned as a reaction force causing overshoot. This amplifies frontal plane foot movement and attenuates foot position awareness, causing less precise postural adjustments and instability. Low resiliency interfaces dissipate energy and thereby moderate overshoot. Low resiliency interface technology is capable of improving stability, which portends improved health for unstable older people in particular.

Adult↗

PubMed1998

Factors associated with ankle injuries. Preventive measures.

A sense of foot position in humans is precise when barefoot, but is distorted by athletic footwear, which accounts for the high frequency of ankle sprains in shod athletes. It is unclear whether taping and rigid and semi-rigid devices protect against ankle sprains, as all of the studies suggesting this are flawed by inadequate controls. If these devices do protect the ankle, it is not through added support but rather through a partial correction of the deceased foot position awareness caused by footwear. Since taping and rigid and semi-rigid devices interfere with normal movement, there is concern that these might actually increase the frequency of injury at the ankle and/or at different locations. In this respect, taping is less of a concern because it interferes least with normal movement. The best solution for reducing ankle sprains in shod athletes is the use of more advanced footwear to retain maximal tactile sensitivity, thereby maintaining an awareness of foot position comparable to that of the barefoot state or perhaps even improving on it.

Ankle Injuries↗

PubMed1997

Balance and vertical impact in sports: role of shoe sole materials.

OBJECTIVE: Athletic shoes and mats are support surface interfaces composed of relatively soft compressible materials designed to protect against injuries occurring in sports through force of vertical impact. Impact remains high with their use because humans land harder with them. We hypothesize that this hard-landing strategy is an attempt by the user to improve stability, by compressing the material to a less destabilizing thinner-stiff variety. We tested this hypothesis by comparing impact and balance on materials consisting of ethyl-vinyl acetate (EVA) foams of varying stiffness, identical to that found in soles of athletic footwear. DESIGN: Randomized-order, crossover trial, controlled comparison, blinded. SETTING: Volunteers were selected from the general community. PARTICIPANTS: A random sample of 12 healthy men from the general population (mean age 30 years, SD +/- 6). Additional selection criteria were absence of disabilities influencing ability to walk, run, and balance, and no history of frequent falls. METHODS: Impact testing and stability measures were performed on the same test day. Ground reaction forces were measured for ten barefoot footfalls. The protocol required stepping forward from perch to surface 4.5 cm below. Stability testing was performed with one-legged standing consisting of placing left foot on top of right for 30 sec, barefoot, eyes open, and gaze straight, with arms to side. Subjects confronted four surface conditions presented in random order: a bare rigid platform, and the platform covered with one of three 2.5-cm-thick materials. RESULTS: Steady state vertical impact was a negative function of interface stiffness, with the softest interface producing the greatest vertical impact, and the stiffest interface the least vertical impact. Vertical impact and stability measures were also negatively related, with the strongest correlation obtained with the softest interface (r = -.87, p < .001). No relation between these variables was obtained for the rigid surface. CONCLUSION: Balance and vertical impact are closely related. This supports the hypothesis that landing hard on soft surfaces is an attempt to transform the interface into a form associated with improved stability. According to these findings, currently available sports shoes and mats are too soft and thick, and should be redesigned to protect the persons using them.

Adult↗

PubMed1997

Foot position awareness in younger and older men: the influence of footwear sole properties.

OBJECTIVES: To test the hypotheses that foot position awareness is related positively to stability, positively to shoe sole hardness, and negatively to shoe sole thickness, and that foot position awareness declines with advancing years. SETTING: Older subjects were consecutive volunteers from a medical clinic; younger subjects were volunteers from the community. DESIGN: Randomized-order, cross-over, controlled comparison. PARTICIPANTS: Older subjects were a random sample of 13 healthy men, mean age 72.58 years, SD +/- 4.50. Younger subjects were a random sample of 13 male subjects from the general population, mean age 28.13 years, SD +/- 3.96. Additional selection criteria were absence of disabilities influencing ability to walk and no history of frequent falls. MEASUREMENTS: Balance failure frequency, defined as falls per 100 meters of beam walking; rearfoot angle in degrees, measured via an optical position measurement system; perceived maximum supination when walking, in degrees, estimated by subjects using a ratio scale; foot position error, in degrees, was defined as the rearfoot angle minus perceived maximum supination. RESULTS: Foot position error during walking: (1) increases with advancing years; footwear conditions absolute mean error for older sample of 15.48 degrees, SE +/- 1.56 degrees, and younger sample 5.44 degrees, SE +/- 1.03 degrees (P > .001); (2) is positively related to stability (r = .367, P < .001); (3) is positively related to midsole thickness (F(1,11) = 19.89, P < .001); (4) is negatively related to midsole hardness (F(2,22) = 29.80, P < .001); (5) correlates best with perceived maximum supination (r = .901, P < .001). CONCLUSION: Foot position awareness is related causally to stability; shoes with thin, hard soles provide better stability for men than those with thick, soft midsoles. Foot position awareness declines with advancing years.

Adult↗

PubMed1997

Hazard of deceptive advertising of athletic footwear.

OBJECTIVES: Athletic footwear are associated with frequent injury that are thought to result from repetitive impact. No scientific data suggest they protect well. Expensive athletic shoes are deceptively advertised to safeguard well through "cushioning impact", yet account for 123% greater injury frequency than the cheapest ones. This study tested the hypothesis that deceptive advertising creates a false sense of security with users of expensive athletic shoes, inducing attenuation of impact moderating behaviour, increased impact, and injury. METHODS: Fifteen young healthy male volunteers confronted four surfaces: a bare force moment platform, and three with this platform covered by identical shoe sole material made to appear different and advertised divergently. Advertising messages suggested superior impact absorption and protection (deceptive message), poor impact absorption and high injury risk (warning message), and unknown impact absorption and safety (neutral message). Ground reaction forces were recorded for 10 barefoot footfalls, according to a protocol requiring stepping forward from perch to a surface 4.5 cm below. RESULTS: Impact varied as a function of advertising message (p < 0.001). Deceptive message equalled neutral message in eliciting higher impact than the warning message and the bare platform. Differences grew with repetitions (p < 0.001). CONCLUSIONS: These data provide a plausible mechanism explaining higher injury frequency in users of expensive athletic shoes. This is the first report to suggest: (1) deceptive advertising of protective devices may represent a public health hazard and may have to be eliminated presumably through regulation; (2) a tendency in humans to be less cautious when using new devices of unknown benefit because of overly positive attitudes associated with new technology and novel devices.

Adult↗

PubMed1995

Proprioception and stability: foot position awareness as a function of age and footwear.

We examined the hypothesis that awareness of foot position in terms of the slope of the weight-bearing surface declines with age. We further postulated that the decline would be due to a change in plantar tactile sensibility, and that footwear would further impair position judgments. We compared 15 men aged over 65 years (mean age 73) with 36 men aged under 40 (mean age 30) in terms of estimates of amplitude and direction of surface slopes. We employed a ratio scale of 0-10 representing actual slopes of 0 degrees-25 degrees in increments of 2.5 degrees. In order to examine whether subjects overestimated high angles they were told that the scale ranged from 0 to 15. We found significant differences between the two groups in terms of estimates and the effect of footwear. Psychophysical functions for estimate of slope were 0.95 for the young when barefoot and 0.71 when shod compared with 0.80 and 0.81 respectively for the older men. We conclude that sensitivity to foot position declines with age, mainly owing to loss of plantar tactile sensitivity. Footwear impairs foot position awareness in both young and old. Loss of foot position awareness may contribute to the frequency of falls in later life.

Adult↗

PubMed1995

Ankle taping improves proprioception before and after exercise in young men.

Ankle sprains are common sports injuries. Inadequate foot position awareness is thought to be the fundamental cause of these injuries. Ankle taping may decrease risk of injury through improving foot position awareness. The benefit of taping is thought to decrease with duration of exercise because of poor tape adherence to human skin. This study was a randomized, crossover, controlled comparison experiment that tested the hypothesis that ankle taping improves foot position awareness before and after exercise. A sample of 24 healthy young blindfolded volunteers, wearing their own athletic shoes, indicated perceived slope direction and estimated slope amplitude when bearing full body weight and standing on a series of blocks. The top slope of the blocks varied between 0 degree and 25 degrees, in 2.5 degrees increments, to orient the plantar surface with respect to the leg toward pronation, supination, plantarflexion, and dorsiflexion, relative to its position on a flat surface. Foot position awareness, which was considered the reciprocal of surface slope estimate error, varied with testing condition, particularly when surface slope was greater than 10 degrees, presumably the most important range considering ankle injuries. In this higher range absolute position error was 4.23 degrees taped, and 5.53 degrees untaped (P < 0.001). Following exercise, in the higher range absolute position error was 2.5% worse when taped and 35.5% worse when untaped (P < 0.001). These data support the hypothesis that ankle taping improves proprioception before and after exercise. They also indicate that foot position awareness declines with exercise. Compared to barefoot data (position error 1.97 degrees), foot position error was 107.5% poorer with athletic footwear when untaped (absolute position error 4.11 degrees), and 58.1% worse when taped (position error 3.13 degrees). This suggests that ankle taping partly corrects impaired proprioception caused by modern athletic footwear and exercise. Footwear could be optimized to reduce the incidence of these injuries.

Adult↗

PubMed1994

Athletic footwear affects balance in men.

Stable equilibrium during locomotion is required for both superior performance of sports and prevention of injuries from falls. A recent report indicated that currently available athletic footwear impairs stability in older men. Since this discovery, if confirmed, seems important to both competitive athletes and the physically active general public, we performed an experiment using similar methods on a younger population. We tested the hypothesis that midsole thickness is negatively, and hardness positively related to dynamic equilibrium, in 17 healthy adult men (mean(s.d.) age 33(11.13) years) via a balance beam method. Subjects walked along a 9-m long beam at 0.5 m s-1 once barefoot and six times wearing identical pairs of experimental shoes which differed only in midsole hardness and thickness which spanned the respective ranges currently available in footwear. Falls from the beam (balance failures) were quantified. Balance failures varied significantly in relation to midsole hardness and thickness, and there was a strong trend toward interaction of these variables (P = 0.09). Midsole hardness was positively related to stability, and midsole thickness was negatively related, which confirms the previous report. Hence, shoes with thick-soft soles, similar to modern athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability. The pair with the poorest stability (A 15-thick; 12.34 balance failures per 100 m) produced 217% more balance failures than those associated with the best stability (A 50-thin; 3.89 balance failures per 100 m). Since most types of athletic footwear and many other shoes incorporate midsoles with hardness and thickness associated with poor stability, we conclude that both athletic performance and public safety could be enhanced through stability optimized footwear.

Adult↗

PubMedDate not supplied

Protective sensation of the plantar aspect of the foot.

The scientific literature suggests that barefoot activity may be beneficial. There is a current trend in recreational barefoot activity in children and adults, and barefoot running among athletes. Although the type of skin over most of the body (hairy skin) seems to be easily injured by painful abrading loads, little is known about protection provided by plantar sensory feedback against damage from excessive wear during barefoot locomotion. To evaluate this, we administered a volley of 35 painful abrading loads to glabrous and hairy skin sites over a 5-min period, and examined its effects for signs of cutaneous injury in a sample of 12 normally shod healthy male subjects. Compared with hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. Furthermore, painful stimulation produced visible redness and hypersensitivity in all subjects at the hairy skin site 24 hr after stimulation, whereas only 8.3% reported hypersensitivity and none showed erythema at the plantar area 1 day later. We found that plantar skin possesses a higher pain threshold to abrading stimuli than hairy skin. In fact, loading of the plantar area was limited to innocuous levels due to intolerable pain. We conclude that plantar skin is well protected through sensory feedback from abrasive injuries when barefoot. This information combined with previous reports suggests that risk of injury when normally shod individuals perform barefoot locomotion should be low.

Adult↗