Manipulation of visual biofeedback during gait with a time delayed adaptive Virtual Mirror Box.

BACKGROUND: A mirror placed in the mid-sagittal plane of the body has been used to reduce phantom limb pain and improve movement function in medical conditions characterised by asymmetrical movement control. The mirrored illusion of unimpaired limb movement during gait might enhance the effect, but a physical mirror is only capable of showing parallel movement of limbs in real time typically while sitting. We aimed to overcome the limitations of physical mirrors by developing and evaluating a Virtual Mirror Box which delays the mirrored image of limbs during gait to ensure temporal congruency with the impaired physical limb. METHODS: An application was developed in the CAREN system's D-Flow software which mirrors selected limbs recorded by real-time motion capture to the contralateral side. To achieve phase shifted movement of limbs during gait, the mirrored virtual limbs are also delayed by a continuously calculated amount derived from past gait events. In order to accommodate non-normal proportions and offsets of pathological gait, the movements are morphed so that the physical and virtual contact events match on the mirrored side. Our method was tested with a trans-femoral amputee walking on a treadmill using his artificial limb. Joint angles of the elbow and knee were compared between the intact and mirrored side using cross correlation, root mean squared difference and correlation coefficients. RESULTS: The time delayed adaptive virtual mirror box produced a symmetrical looking gait of the avatar coupled with a reduction of the difference between the intact and virtual knee and elbow angles (10.86° and 5.34° reduced to 4.99° and 2.54° respectively). Dynamic morphing of the delay caused a non-significant change of toe-off events when compared to delaying by 50% of the previous gait cycle, as opposed to the initial contact events which showed a practically negligible but statistically significant increase (p < 0.05). CONCLUSIONS: Adding an adaptive time delay to the Virtual Mirror Box has extended its use to treadmill gait, for the first time. Dynamic morphing resulted in a compromise between mirrored movement of the intact side and gait events of the virtual limbs matched with physical events of the impaired side. Asymmetrical but repeatable gait is expected to provide even more faithful mirroring.

Physical activity and the risk of developing lung cancer among smokers: a meta-analysis.

OBJECTIVE: To investigate the relationship between physical activity and lung cancer among smokers and whether this relationship differed according to physical activity intensity, smoking status, and gender. DESIGN: Meta-analysis. METHODS: A computerized bibliographical search was conducted in five databases. Study inclusion criteria were: (i) the study population was not diagnosed with lung cancer at baseline; (ii) the study provided information concerning the effect size of physical activity on the risk of developing lung cancer in smokers; and (iii) the study distinguished different physical activity intensity levels. Two authors independently extracted data and assessed the methodological quality. Pooled rate ratios (RR) were calculated for all data, and for subgroups of physical activity intensity, smoking status, and gender. RESULTS: Pooled RRs of 7 cohort studies showed that physical activity was associated with a reduced risk of lung cancer in smokers (RR=0.82, 95% CI=0.77; 0.87). We did not find clear dose-response relationship regarding exercise or smoking intensity, i.e. high levels of physical activity did not show a higher risk reduction than moderate physical activity levels, and the association between physical activity and risk reduction did not differ between heavy and light smokers. The reduced risk associated with physical activity was greater in women than in men (p=0.03), but this finding was based on only one study that reported data on women. CONCLUSIONS: Results of this meta-analysis indicate that leisure time physical activity is associated with reduced risk of developing lung cancer among smokers. Future studies should provide insight into a potential dose-response relationship, and should use reliable and valid physical activity measurements.

Bimanual training for children with cerebral palsy: exploring the effects of Lissajous-based computer gaming.

OBJECTIVE: Hemiplegic cerebral palsy often results in impaired bimanual coordination, partly due to strong coupling between the arms. We aimed at inducing more flexibility in this coupling, to improve bimanual coordination. METHODS: We designed computer games involving simple perceptual goals, based on Lissajous feedback. Such feedback implicitly facilitates the performance of complex rhythmic bimanual coordination patterns. A sample of six children received 9 h of computer training over a 6 weeks period. The effects of this training on functional bimanual performance were explored using the Assisting Hand Assessment (AHA). RESULTS: Gaming performance and bimanual rhythmic antiphase coordination improved after training. The AHA results were mixed. Two children improved significantly, but at a group level no significant effects were found. CONCLUSIONS: The results were evaluated in relation to the specificity of the AHA and the potential benefit of combining the proposed training with dedicated bimanual functional training programs.