Understanding postural control requires considering various mechanisms underlying a person's ability to stand, to walk, and to interact with the environment safely and efficiently. The purpose of this paper is to summarize the functional relation between biomechanical and neurophysiological perspectives related to postural control in both standing and walking based on movement efficiency. Evidence related to the biomechanical and neurophysiological mechanisms is explored as well as the role of proprioceptive input on postural and movement control.

Introduction. Sit-to-stand (SitTS) and stand-to-sit (StandTS) are very important functional tasks that become compromised in stroke patients. As in other voluntary movements, they require an adequate postural control (PC) involving the generation of anticipatory postural adjustments (APAs). In order to give clues for more efficient and directed rehabilitation programs, a deeper knowledge about APAs during challenging and daily life movements is essential. Purpose. To analyze the activation timing of tibialis anterior (TA) and soleus (SOL) muscles during SitTS and StandTS in healthy subjects and in post-stroke patients. Methods. Two groups participated in this study: one composed of ten healthy subjects and the other by ten subjects with a history of stroke and increased H-reflex. Electromyographic activity (EMGa) of SOL and TA was analyzed during SitTS and StandTS in the ipsilateral (IPSI) and the contralateral (CONTRA) limb to the side lesion in stroke subjects, and in one limb in healthy subjects. A force plate was used to identify the movement onset. Results. In both sequences, in the stroke group SOL activation timing occurred prior to movement onset, contrary to the pattern observed in the healthy subjects. Statistically significant differences were found in SOL activation timings between each lower limb of the stroke and healthy groups, but no significant differences were found between the IPSI and the CONTRA limb. The TA activation timing seems to be delayed in the CONTRA limb when compared to the healthy subjects and showed a better organization of TA timing activation in StandTS when compared to SitTS. Conclusion. Compared to healthy subjects, APAs seem to be altered in both limbs of the post-stroke subjects, with the SOL activation timing being anticipated in both SitTS and StandTS.

Stroke leads to significant impairment in upper limb (UL) function. The goal of rehabilitation is the reestablishment of pre-stroke motor stroke skills by stimulating neuroplasticity. Among several rehabilitation approaches, functional electrical stimulation (FES) is highlighted in stroke rehabilitation guidelines as a supplementary therapy alongside the standard care modalities. The aim of this study is to present a comprehensive review regarding the usability of FES in post-stroke UL rehabilitation. Specifically, the factors related to UL rehabilitation that should be considered in FES usability, as well a critical review of the outcomes used to assess FES usability, are presented. This review reinforces the FES as a promising tool to induce neuroplastic modifications in post-stroke rehabilitation by enabling the possibility of delivering intensive periods of treatment with comparatively less demand on human resources. However, the lack of studies evaluating FES usability through motor control outcomes, specifically movement quality indicators, combined with user satisfaction limits the definition of FES optimal therapeutical window for different UL functional tasks. FES systems capable of integrating postural control muscles involving other anatomic regions, such as the trunk, during reaching tasks are required to improve UL function in post-stroke patients.

Context: : Despite extensive research on chronic ankle instability, the findings regarding proprioception have been conflicting and focused only on the injured limb. Also, the different components of proprioception have been evaluated in isolation. Objective: : To evaluate bilateral ankle proprioception in individuals with unilateral ankle instability. Design: : Cohort study. Setting: : Research laboratory center in a university. Patients or Other Participants: : Twenty-four individuals with a history of unilateral ankle sprain and chronic ankle instability (mechanical ankle instability group, n = 10; functional ankle instability [FAI] group, n = 14) and 20 controls. Main Outcome Measure(s): : Ankle active and passive joint position sense, kinesthesia, and force sense. Results: : We observed a significant interaction between the effects of limb and group for kinesthesia (F = 3.27, P = .049). Increased error values were observed in the injured limb of the FAI group compared with the control group (P = .031, Cohen d = 0.47). Differences were also evident for force sense (F = 9.31, P < .001): the FAI group demonstrated increased error versus the control group (injured limb: P < .001, Cohen d = 1.28; uninjured limb: P = .009, Cohen d = 0.89) and the mechanical ankle instability group (uninjured limb: P = .023, Cohen d = 0.76). Conclusions: : Individuals with unilateral FAI had increased error ipsilaterally (injured limb) for inversion movement detection (kinesthesia) and evertor force sense and increased error contralaterally (uninjured limb) for evertor force sense.

This study aims to assess the influence of gait speed (manipulated through cadence) on muscle activity patterns and activation degree during stance.Methods: Thirtyfive healthy individuals participated in this study. Surface electromyographic activity from the gastrocnemius medialis (GM), gluteus maximus (GMax), biceps femoris (BF) and rectus femoris (RF) was acquired with subjects walking at three different speeds.Results: Speed influenced: (1) relative motor activity patterns at heel strike, midstance-propulsion transition and propulsion; (2) the activity level of RF, GMax, GM and BF, in decreasing order, with higher activity at the fastest and slowest speeds.Conclusions: In general, muscle activity was higher at the fastest and slowest speeds than at the self-selected speed and only the activity of the main actions in each subphase remained stable. These findings suggest that gait speeds different from the self-selected speed influence not only activity levels but also relative muscle activity patterns. As a result, caution is advised when choosing standard speeds in gait studies, as this can lead to increased variability in relative muscle activity patterns.