Bilateral motor unit synchronization is functionally organized

To elucidate the neural interactions underlying bimanual coordination, we investigated in 11 participants the bilateral coupling of homologous muscles in an isometric force production task involving fatiguing elbow flexion and extension. We focused on changes in motor unit (MU) synchronization as evident in EMG recordings of relevant muscles. In contrast to a related study on leg muscles, the arm muscles did not exhibit MU synchronization around 16 Hz, consistent with our hypothesis that 16 Hz MU synchronization is linked to balance maintenance. As expected, bilateral MU synchronization was apparent between 8 and 12 Hz and increased with fatigue and more strongly so for extensor than for flexor muscles. MU synchronization in that frequency band is interpreted in terms of common bilateral input and substantiates the idea that common input is functionally organized. Since these findings are consistent with the literature on mirror movements, they suggest that both phenomena may be related.

Measuring psychological consequences of screening: adaptation of the psychological consequences questionnaire into Dutch

OBJECTIVE

To assess the psychometric properties of a Dutch adaptation of an originally Australian instrument measuring the psychological impact of breast cancer screening.

METHODS

The three subscales (emotional, physical, social) of the Psychological Consequences Questionnaire (PCQ) underwent formal linguistic and cultural translation. A total of 524 women under intensive surveillance because of increased breast cancer risk were asked to complete the questionnaire at 2 months prior to screening, at the day of the screening visit preceding the screening, and 1-4 weeks after screening. Acceptability, score distribution, internal consistency, scale structure, responsiveness to change and construct validity were analysed.

RESULTS

Response rates were high (98-94%) and there were very few missing answers and non-unique answers. All scales had Cronbach's alphas > 0.70. The physical and social subscale showed ceiling effects. The item-own scale correlations were only slightly higher than the corresponding item-other scale correlations. Factor analysis showed that the assumed three separate subscales were replicated in our study. Pre- and post-screening effect sizes for the emotional scale were larger than for the other two scales. All PCQ scales correlated with the scales of two other psychological measures (p <or= 0.01). The emotional scale and the total PCQ score were able to differentiate between subgroups varying in affective risk perception (p <or= 0.01).

CONCLUSION

The Dutch PCQ is useful in measuring psychological impact among women under intensive surveillance because of high breast cancer risk.