This study was designed to examine the importance of vision to corrective processes associated with a mechanical perturbation to the limb during goal-directed aiming. With a hand held stylus, under vision and no vision conditions, performers reached to a target represented by the intersection of perpendicular lines. The stylus was connected to an air compressor and engineered such that 80 ms following movement initiation reaches were perturbed by a short air burst either in the direction of, or opposite to, the movement. Spatial position analysis of the limb at early kinematic landmarks revealed that the single direction bursts were successful in advancing and hindering the movement progress. Furthermore, within subject trial-to-trial variability analysis indicated that performers adopted different control strategies for dealing with the perturbations depending on the availability of vision. The present findings suggest that a continuous form of online control is exercised during the early portions of the aiming trajectories. This form of control may be mediated by visual or proprioceptive information.

Learning to write requires the repeated manual production of spatial patterns. It remains unclear whether tracing or copying provides better training: tracing provides accurate and immediate performance feedback, whereas copying may require greater use of memory and recall during training. We asked sixteen adults to copy or trace novel patterns then reproduce these from memory using a stylus and tablet PC. A week later, a retention test was performed. Sophisticated analyses indexed the extent to which participants had learned the dimensions and shape of patterns. We found that participants: (a) showed better shape and dimensional accuracy when tracing; (b) had better shape and dimensional retention immediately after tracing; (c) showed no differences between copying and tracing in their ability to redraw the pattern (shape or dimensions) 1 week later. Our methods provide a useful starting point for examining training and feedback on the generation and recall of spatial patterns.

Objectives: (1) To develop a scale that is useful in evaluating the accuracy of multifrequency bioelectrical impedance analysis (MF-BIA) in the assessment of body water volumes against the accepted gold standard measurements based on isotope-dilution and total body potassium (TBK). (2) To perform a pilot test of the scale. Design: A scale was developed to evaluate the accuracy of MF-BIA in the assessment of body water volumes. Questions were obtained from reading the scientific literature and discussions involving the four authors. Three of these and two additional independent readers pre-tested the scale. A weighting was identified for each question and a pilot test with a sample of 10 articles (different to those used for the questionnaire performance) was conducted. A further validation was carried out with a second set of 20 articles and two additional independent readers. Results: The kappa statistic expressing the level of agreement between pairs of the first three authors using this scale with 10 articles, was 0.3, 0.4 and 0.6 after the first attempt. A second evaluation after specific changes improved the agreement to 0.8, 0.6 and 0.8. The mean score for 10 articles was 252 AE 36 points from a total score of 400 (63 AE 9%). The evaluation with the second set of 20 articles resulted in a k of 0.7 from two pairs of authors. The evaluation with two additional reviewers resulted in a k ¼ 0.7. Conclusion: A tool has been developed to assess the accuracy of the MF-BIA technique and to identify methodological components, plan future studies and critically evaluate data in this area. It is likely that this tool may also be used to assess the accuracy of single frequency studies.

Objective: We investigated the ability of whole body and segmental multiple frequency bioelectrical impedance (MFBIA) to detect peritoneal¯uid in peritoneal dialysis patients. Design: Prospective study. Setting: Teaching hospital renal unit. Subjects: Patients on regular peritoneal dialysis. Interventions: Whole body and segmental MFBIA measurements before and after drainage of peritoneal¯uid. Results: Changes estimated by MFBIA in total body water ( 7 0.4 (0.8) litres) and extracellular water ( 7 0.3 (0.3) litres) were much lower than the actual changes (2.0 (0.4) litres), P`0.0001. Derived resistances R ecf and R icf increased signi®cantly for the trunk but not for total body measurements and changes did not correlate with volumes of¯uid drained. Conclusions: MFBIA is limited in its ability to detect intraperitoneal¯uid, using both whole body and segmental techniques.