Adaptation-level and theory of signal detection: an examination and integration of two judgment models for voluntary stimulus generalization.
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Manual asymmetries in weight discrimination were investigated by testing 50 subjects with their left hand and 52 with their right hand, the groups being approximately balanced for sex and hand preference. Performance was better for the left-tested group, and for strongly handed males tested with the dominant hand. Female performance was unrelated to handedness. There was no overall superiority due to sex, males being superior with the dominant hand and females with the nondominant hand. The results are interpreted in terms of spatial hemisphere involvement, hand dominance, and the greater hemispheric specialization of males.
This paper analyzes demographic, social, psychological, and behavioral correlates of weight loss and maintenance in a group of 89 middle-aged men. Measures were collected before and after a 15-week intervention program and at 3-month and 1-year follow-up evaluations. Associations were examined through 2 years of follow-up observation. Principal findings were (a) a strong inverse relationship between prior participation in an organized weight control program and both short- and long-term weight loss; (b) a positive association between efficacy expectations and weight loss; (c) a positive association between attendance at treatment sessions and weight loss; (d) an inverse relationship between spouse attendance and weight loss; and (e) positive associations between weight loss and perceived social support, reported improvement in eating behavior, reported improvement in exercise behavior, and affirmative response to relapse episodes following treatment.
Mothers of 107 preschool children estimated their child's weight status, and the accuracy of these estimates was examined. The majority of mothers (72%) were accurate. Of those who were inaccurate, 83% had underestimated the child's weight status, whereas only 17% had overestimated. Mothers of heavier children were more likely to underestimate their child's weight status.
A group of adult women (n = 351) were assessed on a number of psychological, behavioral, and body composition measures including weight preoccupation and leisure-time physical activity participation. The purpose of the study was twofold. It was intended (a) to investigate whether excessive exercises have specific characteristics in common other than that they exercise a great deal and (b) to identify the degree of relationship between exercising and weight preoccupation, and the extent to which those classified as excessive on either dimension have psychological characteristics in common. Results indicated that excessive exercisers reported greater body satisfaction and body focus, were less emotionally reactive (neurotic), and more extraverted than nonexercisers. Although some researchers have reported psychological similarities between excessive exercisers and women with eating disturbances, our data do not entirely support that point of view. While excessive exercise was associated with a decrease in body dissatisfaction and was negatively related to neuroticism, weight preoccupation was associated with an increase in body dissatisfaction and was positively related to neuroticism. However, one characteristic that both excessive groups shared, and that significantly differentiated them from their nonexcessive counterparts, was their high level of body focus. These findings led us to test the body focus x neuroticism interaction on both exercise participation and weight preoccupation. Results indicated a highly significant interaction on weight preoccupation. However, only the two main effects were significantly related to exercise.
OBJECTIVES: To determine the effect of 3 prosthetic mass conditions on selected physiologic responses during multiple speed treadmill walking in persons with transtibial amputation. DESIGN: A repeated-measures design for 3 prosthetic mass conditions and 5 walking speeds. SETTING: University research laboratory. PARTICIPANTS: Eight ambulatory men with unilateral traumatic transtibial amputation. INTERVENTIONS: The 3 prosthetic mass conditions were 60%, 80%, and 100% of the estimated intact limb below-knee mass. The multiple-speed treadmill walking test (4min at each speed: 54, 67, 80, 94, 107m/min) was performed on an instrumented treadmill according to randomly assigned mass conditions. MAIN OUTCOME MEASURES: Oxygen consumption, gait efficiency, relative exercise intensity (percentage of age-predicted maximal heart rate), and stride frequency. RESULTS: Prosthetic mass did not significantly alter oxygen consumption or gait efficiency (P>.05). From the 60% to the 100% prosthetic mass conditions, relative exercise intensity significantly increased and stride frequency significantly decreased (P<.05). CONCLUSIONS: A heavier prosthesis (up to 100% of estimated intact limb below-knee mass) did not significantly increase the energy costs of walking for the 5 speeds examined. Further study of gait symmetry with the use of a heavier prosthesis is warranted.
OBJECTIVE: To determine whether the ability to discriminate weights remained accurate after anterior cruciate ligament (ACL) injury. DESIGN: Descriptive case series. SETTING: Outpatient physical therapy. PARTICIPANTS: Convenience sample of 10 participants with unilateral ACL injuries (age, 27.1+/-8.2 y) and 8 healthy controls (age, 22.6+/-2.8 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Weber fractions, expressed as percentage differences from the standard weight (3.00 kg) that could be reliably detected (75% correct level), were derived from each leg to provide an index of proprioceptive acuity for weight discrimination. Subjective ratings of knee function (Activities of Daily Living Scale of the Knee Outcome Survey) and measurements of quadriceps strength (peak isometric torque). RESULTS: The ACL group exhibited a reduced acuity to detect differences in weight on the injured, as compared with the uninjured, side as reflected in the increase in Weber fractions (mean, 6.7%+/-2.3% vs 4.8%+/-1.1%, respectively; P = .043). No such difference in acuity between legs was detected in healthy controls (mean right and left, 5.4%+/-1.4% vs 5.7%+/-1.3%, respectively, P = .99). CONCLUSIONS: Proprioceptive acuity for weight discrimination was significantly reduced after an ACL injury, possibly reflecting deficits in the ability to properly calibrate force signals generated while muscles are actively contracting, as a result of a loss in ligamentous sensory innervation.
The perception that weight reduction is rarely successful is, in fact, a misperception. Between 1999-2000 and 2001-2002, there were no significant changes among adults in the prevalence of overweight, obesity, or extreme obesity, or among children aged 6 through 19 years in the prevalence of at risk for overweight. The National Heart, Lung, and Blood Institute defines successful long-term weight loss as an intentional reduction of 10% from baseline maintained for 1 year. Modest weight loss is not only beneficial but also achievable for persons with overweight and obesity. Of the Americans who have tried to lose weight, almost 50% have maintained their weight loss successfully for at least 1 year. The remaining half, those who seem unable to prevent or reverse their obesity, challenge dietetics professionals to mobilize resources, confront issues at the heart of the obesity epidemic, and develop new solutions. Work to date has paid off for millions of persons. We have stopped the epidemic of obesity. Now it is time to do more by joining health care practitioners with all other stakeholders in the effort to prevent and reverse it.
The purpose of the current experiment was to investigate the amount (standard deviation (S.D.) and coefficient of variation (CV)) and structure (approximate entropy (ApEn)) of force variability at very low force levels. Participants produced isometric force output of index finger abduction at five levels (0.4, 0.8, 1.0, 2.0, and 4.0 N) with high and low visual feedback gain. The findings showed that: subjects scaled their force output to the targets; S.D. increased non-linearly with force level and decreased with visual gain; and CV decreased with force level as well as visual gain. ApEn of the force output did not change as a function of force level, although the high gain increased ApEn in contrast to low gain. It is proposed that the recruitment of additional motor units at very low force levels does not significantly alter the structure of the force output, although it does increase the magnitude of force and its amount of variability. Overall, the findings provide evidence that the amount and structure of motor variability can be influenced by separate control processes at low force levels.
When we repetitively lift an object, the balance between grip force normal to the object's surface and load force tangential to the object's surface is accurately programmed to match the physical object properties within a few lifts. Here, we ask if the accuracy of grip force scaling to object weight and the transfer of weight-related information from one hand to the other is impaired in cerebellar degeneration. Subjects with generalized cerebellar degenerative disorders were tested. Subjects first repeatedly lifted a constant weight with the dominant hand, followed by a series of lifts of the same weight with the opposite hand. The experiments were performed with a light and a heavy weight. Patients and controls scaled the grip force output differentially to different weight. The comparison of grip force scaling for the first and last lifts with a constant weight demonstrated that healthy subjects and cerebellar patients adjusted grip forces more accurately to a specific weight with increasing number of lifts performed at each hand. The ability to transfer weight-related information from one hand to the other was analyzed by comparing the last lift with a constant weight of the dominant hand with the first lift of the same weight performed by the opposite hand. Healthy subjects scaled the grip force output precisely to a given weight immediately after a change in hand, suggesting that they succeeded to transfer weight-related information in between both hemispheres. In contrast, cerebellar patients produced an inaccurate grip force overshoot when lifting a given weight with the opposite hand. Our data suggest that the cerebellum plays a major role for the generalization of weight-related information during object manipulation.
BACKGROUND: Many patients have described changes in taste perception after weight loss surgery. Our hypothesis was that patients develop postoperative changes in taste that vary by bariatric procedure. METHODS: Patients who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB) or laparoscopic adjustable gastric banding (LAGB) completed a 23-question institutional review board-approved survey postoperatively regarding their degree and type of taste changes and food aversion and how these influenced their eating habits. RESULTS: A total of 127 patients participated. After removing the inadequately completed surveys, 82 LRYGB and 28 LAGB patients were included. Of these, 87% of LRYGB and 69% of LAGB patients believed taste is important to the enjoyment of food. More LRYGB patients (82%) than LAGB patients (46%) reported a change in the taste of food or beverages after surgery (P <.001). In addition, 92% of LAGB versus 59% of LRYGB patients characterized the change as a decrease in the intensity of taste (P <.05). Additionally, 68% of LRYGB and 67% of LAGB patients found certain foods repulsive and had developed aversions. Also, 66% of LRYGB and 70% of LAGB patients believed the taste changes were greater than expected preoperatively. Most patients (83% of LRYGB and 69% of LAGB patients) agreed that the loss of taste led to better weight loss. CONCLUSION: Although most LRYGB and many LAGB patients experienced taste changes and food repulsion postoperatively, procedural differences were found in these taste changes. Taste changes need to be investigated further as a possible mechanism of weight loss after bariatric surgery.