Where data are to be pooled for international studies, analysis of DIF by culture is essential. Where DIF is observed, adjustments can be made to allow for cultural differences in outcome measurement.

Background and Purpose-Chronic hemiparetic patients often retain the ability to manage activities requiring both hands, either through the use of the affected arm or compensation with the unaffected limb. A measure of this overall ability was developed by adapting and validating the ABILHAND questionnaire through the Rasch measurement model. ABILHAND measures the patient's perceived difficulty in performing everyday manual activities. Methods-One hundred three chronic (Ͼ6 months) stroke outpatients (62% men; mean age, 63 years) were assessed (74 in Belgium, 29 in Italy). They lived at home and walked independently and were screened for the absence of major cognitive deficits (dementia, aphasia, hemineglect). The patients were administered the ABILHAND questionnaire, the Brunnström upper limb motricity test, the box-and-block manual dexterity test, the Semmes-Weinstein tactile sensation test, and the Geriatric Depression Scale. The brain lesion type and site were recorded. ABILHAND results were analyzed with the use of Winsteps Rasch software. Results-The Rasch refinement of ABILHAND led to a change from the original unimanual and bimanual 56-item, 4-level scale to a bimanual 23-item, 3-level scale. The resulting ability scale had sufficient sensitivity to be clinically useful. Rasch reliability was 0.90, and the item-difficulty hierarchy was stable across demographic and clinical subgroups. Grip strength, motricity, dexterity, and depression were significantly correlated with the ABILHAND measures. Key Words: arm Ⅲ disability evaluation Ⅲ rehabilitation Ⅲ stroke P oststroke hemiplegia is one of the most prevalent forms of motor disability, affecting approximately 1% of the population. 1 Although most current stroke survivors achieve an autonomous form of gait, a satisfactory recovery (if any) of the affected upper limb function is much more rare. Conclusions-TheAlthough several tests are available 2-4 for measuring upper limb function in terms of grip strength, dexterity, sensation, and performance in standardized manipulative tasks, the measurements are all made at the focal impairment level. 5 The actual disability, however, is far from linearly related to the underlying impairments. 6 It depends on complex interactions between upper limb function and compensatory behaviors of the person, such as using the unaffected limb or dividing complex movements into simpler ones. Moreover, the learning of new motor processes is influenced by the subject's motivational and emotional status, which is likely to be impaired by stroke. 7 Manual ability may be defined as the capacity to manage daily activities requiring the use of the upper limbs, whatever the strategies involved. Therefore, it should be measured per se and not simply inferred from focal impairments. Since it is a behavior, manual ability belongs to the domain of latent variables concealed within the person, such as pain, depression, and intelligence. The "amount" of manual ability can be inferred from observed activities and/or a patient's perceived difficul...

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Objective: To study hand impairments and their relationship with manual ability in children with cerebral palsy. Design: Cross-sectional survey. Patients: A total of 101 children with cerebral palsy (mean age 10 years, age range 6-15 years) were assessed. Methods: Three motor and 3 sensory impairments were measured on both hands. Motor impairments included grip strength (Jamar dynamometer), gross manual dexterity (Box and Block Test) and fine finger dexterity (Purdue Pegboard Test). Sensory impairments included tactile pressure detection (Semmes-Weinstein aesthesiometer), stereognosis (Manual Form Perception Test) and proprioception (passive mobilization of the metacarpophalangeal joints). Manual ability was measured with the ABILHAND-Kids questionnaire. The relationship between hand impairments and manual ability was studied through correlation coefficients and a multiple linear forward stepwise regression analysis. Results: Motor impairments were markedly more prevalent than sensory ones. Gross manual dexterity on the dominant hand and grip strength on the non-dominant hand were the best independent predictors of the children's manual ability, predicting 58% of its variance. Conclusion: Hand impairments and manual ability are not related in a predictable straightforward relationship. It is important that, besides hand impairments, manual ability is also measured and treated, as it is not simply the integration of hand functions in daily activities.

Objective: To study hand impairments and their relationship with manual ability in children with cerebral palsy. Design: Cross-sectional survey. Patients: A total of 101 children with cerebral palsy (mean age 10 years, age range 6-15 years) were assessed. Methods: Three motor and 3 sensory impairments were measured on both hands. Motor impairments included grip strength (Jamar dynamometer), gross manual dexterity (Box and Block Test) and fine finger dexterity (Purdue Pegboard Test). Sensory impairments included tactile pressure detection (Semmes-Weinstein aesthesiometer), stereognosis (Manual Form Perception Test) and proprioception (passive mobilization of the metacarpophalangeal joints). Manual ability was measured with the ABILHAND-Kids questionnaire. The relationship between hand impairments and manual ability was studied through correlation coefficients and a multiple linear forward stepwise regression analysis. Results: Motor impairments were markedly more prevalent than sensory ones. Gross manual dexterity on the dominant hand and grip strength on the non-dominant hand were the best independent predictors of the children's manual ability, predicting 58% of its variance. Conclusion: Hand impairments and manual ability are not related in a predictable straightforward relationship. It is important that, besides hand impairments, manual ability is also measured and treated, as it is not simply the integration of hand functions in daily activities.

ABILHAND-Kids is a functional scale specifically developed to measure manual ability in children with CP providing guidelines for goal setting in treatment planning. Its range and measurement precision are appropriate for clinical practice.

In many areas of the world that lack a transportation infrastructure, people routinely carry extraordinary loads supported by their heads, for example the Sherpa of the Himalayas and the women of East Africa. It has previously been shown that African women from the Kikuyu and Luo tribes can carry loads substantially more cheaply than army recruits; however, the mechanism for their economy has remained unknown. Here we investigate, using a force platform, the mechanics of carrying head-supported loads by Kikuyu and Luo women. The weight-specific mechanical work, required to maintain the motion of the common centre of mass of the body and load, decreases with load in the African women, whereas it increases in control subjects. The decrease in work by the African women is a result of a greater conservation of mechanical energy resulting from an improved pendulum-like transfer of energy during each step, back and forth between gravitational potential energy and kinetic energy of the centre of mass.

Investigating cyclic vertical arm movements with an instrumented hand-held load in an airplane undergoing parabolic flight profiles allowed us to determine how humans modulate their grip force when the gravitational and the inertial components of the load force are varied independently. Eight subjects participated in this study; four had already experienced parabolic flights and four had not. The subjects were asked to move the load up and down continuously at three different gravitational conditions (1 g, 1.8 g, and 0 g). At 1 g, the grip force precisely anticipated the fluctuations in the load force, which was maximum at the bottom of the object trajectory and minimum at the top. When gravity changed, the temporal coupling between grip force and load force persisted for all subjects from the first parabola. At 0 g, the grip force was accurately adjusted to the two load force peaks occurring at the two opposite extremes of the trajectory due to the absence of weight. While the experienced subjects exerted a grip force appropriate to a new combination of weight and inertia since their first trial, the inexperienced subjects dramatically increased their grip when faced with either high or low force levels for the first time. Then they progressively released their grip until a continuous grip-load force relationship with regard to 1 g was established after the fifth parabola. We suggest that a central representation of the new gravitational field was rapidly acquired through the incoming vestibular and somatic sensory information.