Reaching from standing requires simultaneous adjustments of focal and postural task elements. We investigated the ability of people with stroke to stabilize the endpoint trajectory while maintaining balance during standing reaches. Nineteen stroke and 11 age-equivalent healthy subjects reached toward a target (n=30 trials) located beyond arm length from standing. Endpoint and center of mass (COM) trajectories were analyzed using the uncontrolled manifold (UCM) approach, with segment angles as elemental variables. A Synergy Index (SI) represented the normalized difference between segment angle combinations leading to endpoint or COM trajectory stabilization (V_UCM) and lack of stabilisation (in an orthogonal space, V_ORT). A higher SI reflects greater stability. In both groups, the endpoint SI (SI_END) decreased in parallel with endpoint velocity and returned close to baseline at the end of the movement. The range of SI_END was significantly greater in stroke (median: 0.87; QR:0.54) compared to healthy subjects (median: 0.58; QR:0.33; p=0.009). In both groups, the lowest SI_END occurred at the endpoint peak velocity, while the minimal SI_END of the stroke group (median: 0.51; QR:0.41) was lower than the healthy group (median: 0.25; QR:0.50; p=0.033). The COM SI (SI_COM) remained stable in both groups (~0.8). The maintenance of a high SI_COM despite a large reduction of SI_END in stroke subjects suggests that kinematic redundancy was effectively used to stabilize the COM position, but less so for endpoint position stabilization. Both focal and postural task elements should be considered when analyzing whole-body reaching deficits in patients with stroke.

Inertial measurement units (IMUs) have been used increasingly to characterize long-track speed skating. We aimed to estimate the accuracy of IMUs for use in phase identification of long-track speed skating. Twelve healthy competitive athletes on a university long-track speed skating team participated in this study. Foot pressure, acceleration and knee joint angle were recorded during a 1000-m speed skating trial using the foot pressure system and IMUs. The foot contact and foot-off timing were identified using three methods (kinetic, acceleration and integrated detection) and the stance time was also calculated. Kinetic detection was used as the gold standard measure. Repeated analysis of variance, intra-class coefficients (ICCs) and Bland-Altman plots were used to estimate the extent of agreement between the detection methods. The stance time computed using the acceleration and integrated detection methods did not differ by more than 3.6% from the gold standard measure. The ICCs ranged between 0.657 and 0.927 for the acceleration detection method and 0.700 and 0.948 for the integrated detection method. The limits of agreement were between 90.1% and 96.1% for the average stance time. Phase identification using acceleration and integrated detection methods is valid for evaluating the kinematic characteristics during long-track speed skating.

Mild cognitive impairment (MCI) is considered to be the limit between the cognitive changes of aging and early dementia; thus, discriminating between participants with and without MCI is important. In the present study, we aimed to examine the differences in the cerebral oxyhemoglobin signal between individuals with and without MCI. The cerebral oxyhemoglobin signal was measured when the participants (young and elderly controls as well as patients with MCI) performed category fluency, finger tapping, and dual tasks using head-mounted near-infrared spectroscopy; the results were compared between the groups. The cerebral oxyhemoglobin signal trended toward the highest values during the category fluency task in young participants and during the finger-tapping task in elderly participants regardless of the MCI status. The area under the curve was approximately 0.5, indicating a low discrimination ability between elderly participants with and without MCI. The measurement of the blood flow in the prefrontal cortex may not accurately quantify cognitive and motor performance to detect MCI. Finger tapping may increase cerebral blood flow in individuals with and without MCI during the task.