Persistence of motor-equivalent postural fluctuations during bipedal quiet standing

Theoretical and empirical work indicates that the central nervous system is able to stabilize motor performance by selectively suppressing task-relevant variability (TRV), while allowing task-equivalent variability (TEV) to occur. During unperturbed bipedal standing, it has previously been observed that, for task variables such as the whole-body center of mass (CoM), TEV exceeds TRV in amplitude. However, selective control (and correction) of TRV should also lead to different temporal characteristics, with TEV exhibiting higher temporal persistence compared to TRV. The present study was specifically designed to test this prediction. Kinematics of prolonged quiet standing (5 minutes) was measured in fourteen healthy young participants, with eyes closed. Using the uncontrolled manifold analysis, postural variability in six sagittal joint angles was decomposed into TEV and TRV with respect to four task variables: (1) center of mass (CoM) position, (2) head position, (3) trunk orientation and (4) head orientation. Persistence of fluctuations within the two variability components was quantified by the time-lagged auto-correlation, with eight time lags between 1 and 128 seconds. The pattern of results differed between task variables. For three of the four task variables (CoM position, head position, trunk orientation), TEV significantly exceeded TRV over the entire 300 s-period.The autocorrelation analysis confirmed our main hypothesis for CoM position and head position: at intermediate and longer time delays, TEV exhibited higher persistence than TRV. Trunk orientation showed a similar trend, while head orientation did not show a systematic difference between TEV and TRV persistence. The combination of temporal and task-equivalent analyses in the present study allow a refined characterization of the dynamic control processes underlying the stabilization of upright standing. The results confirm the prediction, derived from computational motor control, that task-equivalent fluctuations for specific task variables show higher temporal persistence compared to task-relevant fluctuations

Relationship between lower limb muscle strength and 6-minute walk test performance in stroke patients

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Could mobilty performance measures be used to evaluate wheelchair skills?

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Could mobilty performance measures be used to evaluate wheelchair skills?

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Perceptual weighting of pain behaviours of others, not information integration, varies with expertise.

International audienceBeing able to estimate effort pain in patients is important for health care providers working in physical rehabilitation services. Previous studies have shown that clinicians and physiotherapists underestimate patients' pain. METHODS: The present study examined how two sources of visual information, namely body kinematics (movement speed and postural constraints) and facial expressions are integrated in order to estimate effort pain magnitude experienced by a paraplegic person performing a sitting pivot transfer. In addition, the effect of familiarity with paraplegia on judgment was assessed by comparing performance among physiotherapists, paraplegic patients and unfamiliar participants. Functional measurement was used to determine the psychophysical law of visual information integration carried by pain behaviours (guarding and facial expression). RESULTS: Results indicate that guarding behaviour (specified by movement speed) carried important information for perceived effort pain independently of familiarity. In contrast, facial expression of pain was relevant only to unfamiliar and physiotherapist participants and not to paraplegic participants. Even if physiotherapists underestimated effort pain as compared to the other groups, they relied more strongly on facial expression, than other participants, in their estimation of effort pain expressed by a paraplegic patient. CONCLUSIONS: These results bring further insights into understanding physiotherapists' perception of patients' pain. In order to improve their ability to adapt the difficulty of the rehabilitation sessions, they should learn to raise their global level of pain magnitude estimation (for example, by performing themselves the body movement) instead of overweighting facial pain expression signals