In the present report, we investigated changes in corticomotor excitability associated with unilateral knee dysfunction secondary to anterior cruciate ligament (ACL) injury. Ten participants, each with a previous history of unilateral ACL injury (median time post-injury 22 months) and eight healthy controls underwent transcranial magnetic stimulation (TMS) to assess excitability of the lower limb motor representation. Resting motor thresholds (RMTs) and stimulus response curves were measured at rest, while amplitude of motor evoked potentials and silent period duration were measured during active contraction. Correlations between these indices of excitability and three clinical measures of knee function were identified. Paired comparisons of indices by hemisphere revealed an asymmetry only in RMTs, which were significantly reduced on the side of injury in the ACL group. Correlations with clinical measures showed that the extent of quadriceps motor representation, as reflected by the steepness of SR curves, was strongly associated with quadriceps strength (r 2=0.71) on the injured side. The RMT asymmetry reported here in the context of ACL injury is consistent with other recent reports describing enhanced excitability of corticomotor projections targeting muscles adjacent to an immobilized or a painful joint. In such conditions, alterations in the quantity and quality of sensory feedback from the affected limb may underlie the rise in cortical excitability.

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The Journal of Physiology and British Journal of Pharmacology jointly published an editorial series in 2011 to improve standards in statistical reporting and data analysis. It is not known whether reporting practices changed in response to the editorial advice. We conducted a cross-sectional analysis of reporting practices in a random sample of research papers published in these journals before (n = 202) and after (n = 199) publication of the editorial advice. Descriptive data are presented. There was no evidence that reporting practices improved following publication of the editorial advice. Overall, 76-84% of papers with written measures that summarized data variability used standard errors of the mean, and 90-96% of papers did not report exact p-values for primary analyses and post-hoc tests. 76-84% of papers that plotted measures to summarize data variability used standard errors of the mean, and only 2-4% of papers plotted raw data used to calculate variability. Of papers that reported p-values between 0.05 and 0.1, 56-63% interpreted these as trends or statistically significant. Implied or gross spin was noted incidentally in papers before (n = 10) and after (n = 9) the editorial advice was published. Overall, poor statistical reporting, inadequate data presentation and spin were present before and after the editorial advice was published. While the scientific community continues to implement strategies for improving reporting practices, our results indicate stronger incentives or enforcements are needed.

Key pointsr The human gastrocnemius muscle is slack at its shortest lengths in vivo. We hypothesised that when the muscle is lengthened slack is taken up progressively, first in some muscle fascicles, then in others.r A new, quasi-three-dimensional ultrasound imaging method was used to test this hypothesis directly. Contrary to our prediction, the slack was taken up nearly simultaneously in muscle fascicles located throughout the gastrocnemius muscle.r Dynamic three-dimensional reconstructions indicated that, over the range of lengths that was investigated, passive changes in the length of gastrocnemius muscle-tendon units are due to changes in the length of both muscle fascicles and tendinous structures, in approximately equal measure. Changes in the alignment of muscle fascicles and the curvature of aponeuroses have a negligible contribution to change in muscle length.r These findings give insights into how skeletal muscles change their lengths in vivo. AbstractThe mechanisms by which skeletal muscles lengthen and shorten are potentially complex. When the relaxed human gastrocnemius muscle is at its shortest in vivo lengths it falls slack (i.e. it does not exert any passive tension). It has been hypothesised that when the muscle is passively lengthened, slack is progressively taken up, first in some muscle fascicles then in others. Two-dimensional imaging methods suggest that, once the slack is taken up, changes in muscle length are mediated primarily by changes in the lengths of the tendinous components of the muscle. The aims of this study were to test the hypothesis that there is progressive engagement of relaxed muscle fascicles, and to quantify changes in the length and three-dimensional orientation of muscle fascicles and tendinous structures during passive changes in muscle length. Ultrasound imaging was used to determine the location, in an ultrasound image plane, of the proximal and distal ends of muscle fascicles at 14 sites in the human gastrocnemius muscle as the ankle was rotated passively through its full range. A three-dimensional motion analysis system recorded the location and orientation of the ultrasound image plane and the leg. These data were used to generate dynamic three-dimensional reconstructions of the architecture of the muscle fascicles and aponeuroses. There was considerable variability in the measured muscle lengths at which the slack was taken up in individual muscle fascicles. However, that variability was not much greater than the error associated with the measurement procedure. An analysis of these data which took into account the possible correlations between errors showed that, contrary to our earlier hypothesis, muscle fascicles are not progressively engaged during passive lengthening of the human gastrocnemius. Instead, the slack is taken up nearly simultaneously in all muscle fascicles. Once the muscle is lengthened sufficiently to take up the slack, about half of the subsequent increase in muscle length is due to elongation of the tendinous structures and half is due to ...