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The vertical toe position at minimum toe clearance (MTC) in the swing phase is critical for walking safety. Consequently, the joints involved should be strictly controlled and coordinated to stabilize the foot at MTC. The uncontrolled manifold (UCM) hypothesis framework has been used to determine the existence of synergies that stabilize relevant performance variables during walking. However, no study investigated the presence of a multi-joint synergy stabilizing the foot position at MTC and the effects of age and walking speed on this synergy. Is there a multi-joint synergy stabilizing MTC during treadmill walking? Does it depend on the persons' age and walking speed? Kinematic data from 23 young and 15 older adults were analyzed using the UCM approach. The participants walked on a treadmill at three speeds: slow, self-selected, and fast. The sagittal and frontal joint angles from the swing and stance legs and pelvis obliquity were used as motor elements and the vertical toe position at MTC was the performance variable. The variances in the joint space that affected (V ORT , 'bad' variance) and did not affect (V UCM , 'good' variance) the toe position at MTC and the synergy index (ΔV) were computed. The ΔV >0 was revealed for all subjects. Walking speed did not affect ΔV in older adults, whereas ΔV reduced with speed in young adults. ΔV was higher for older than for young adults at self-selected and fast speeds, owing to a lower V ORT in the older group. The vertical toe position at MTC was stabilized by a strong multi-joint synergy. In older adults, this synergy was stronger, as they were better at limiting V ORT than young adults. Reduced V ORT in older adults could be caused by more constrained walking, which may be associated with anxiety due to walking on a treadmill. • A multi-joint synergy (ΔV Z) stabilizes the minimum toe clearance (MTC) in walking. • ΔV Z is higher and variances (V UCM and V ORT) are lower at MTC than in the first half of swing phase. • The ΔV Z and V ORT reduced in young but not in older adults when walking in fast speed. • Older adults showed higher ΔV Z and lower V ORT than young adults. • A reduced V ORT in older adults may be a compensatory strategy adopted to constraint the MTC. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) can affect hand function since the beginning of the motor symptoms. To compare the ability of different hand function tests to: 1) distinguish individuals with PD from healthy controls; 2) differentiate stages of the disease; and 3) indicate changes over time due to disease progression. Twenty-four individuals with PD (Hoehn and Yahr: I–III) and 24 age- and sex-matched controls performed the Jebsen-Taylor Hand Function Test (JTHFT), the Nine-Hole Peg Test (9HPT), and the maximum grip and the maximum pinch strength tests using their right and left hands. Eight individuals with PD (six females and two males) were reassessed after 18 months. The ROC analyses and Mann–Whitney U tests (for disease progression) using the average performance of the hands were done. Individuals with PD presented worse test performances than controls, except for the writing subtest of the JTHFT and the grip strength test. The JTHFT without the writing subtest (JTHFTnoW) was the most accurate to discriminate PD from controls (AUC = 0.899; sensitivity 75% and specificity 95.8%). The 9HPT and the simulated feeding and moving large, light objects JTHFT subtests were sensitive to distinguish stages, while the 9HPT, the moving small, common objects JTHFT subtest, and the grip strength were sensitive to changes with disease progression. The JTHFTnoW was highly discriminative of the hand function impairments in PD. TwoJTHFT subtests were the most sensitives to distinguish PD stages (i.e. simulated feeding JTHFT subtest) and disease progression (i.e. moving small, common objects JTHFT subtest). [ABSTRACT FROM AUTHOR]