Anticipatory postural adjustments in older versus young adults: a systematic review and meta-analysis.

BACKGROUND: Anticipatory postural adjustments (APAs) are a feedforward mechanism triggered in advance to a predictable perturbation, to help the individual counteract mechanical effects that the disturbance may cause. Whether or not this strategy is compromised in the elderly is not a consensus in the literature. METHODS: In this systematic review with meta-analysis, we investigated aging effects on postural control, based on anticipatory postural adjustments (APAs). We selected 11 eligible articles of the following databases: Lilacs, SciELO, PubMed, Cochrane Central, Embase, and CINAHL, involving 324 research participants, assessing their methodological quality and extracting electromyographic, posturographic, and kinematic measurements. We included studies that investigated the occurrence of APAs in healthy younger and older adults, published before 10th August 2022, in English. Studies involving participant with conditions that may affect balance or that did not report measures of onset or amplitude of electromyography (EMG), COP, or kinematics were excluded. To analyze the aggregated results from these studies, we performed the analysis based on the outcome measures (EMG, COP, or kinematic measures) used in individual studies. We calculated differences between younger and older adult groups as the mean differences between the groups and the estimated effect. Egger's test was conducted to evaluate whether this meta-analysis had publication bias. RESULTS: Through this review, older adults showed no significant difference in the velocity to perform a movement compared to the younger adults (MD 0.95, 95% CI -0.86, 2.76, I2 = 82%), but both muscle onset and center of pressure (COP) onset were significantly more delayed in older than in younger adults: erector spinae (MD -31.44, 95% CI -61.79, -1.09, I2 = 95%); rectus abdominis (RA) (MD -31.51, 95% CI -70.58, -3.57, I2 = 85%); tibialis anterior (TA) (MD -44.70, 95% CI -94.30, 4.91, I2 = 63%); soleus (SOL) (MD -37.74, 95% CI -65.43, -10.05, I2 = 91%); gastrocnemius (GAS) (MD -120.59, 95% CI -206.70, -34.49, I2 = 94%); quadriceps (Q) (MD -17.42, 95% CI -34.73, -0.12, I2 = 0%); biceps femoris (BF) (MD -117.47, 95% CI -192.55, -42.70, I2 = 97%); COP onset (MD -45.28, 95% CI -89.57, -0.98, I2 = 93%), and COP apa (COPapa) (MD 2.35, 95% CI -0.09, 4.79, I2 = 64%). These changes did not seem to be linked to the speed of movement but possibly to age-related physiological changes that indicated decreased motor control during APAs in older adults. CONCLUSIONS: Older adults use different postural strategies that aim to increase the safety margin and stabilize the body to perform the movement, according to the requirements imposed, and this should be considered in rehabilitation protocols. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD420119143198.

Comparison of Static Balance Control in Infected Htlv-1 Subjects with Different Tsp/Ham Diagnosis.

(1) Background: Tropical spastic paraparesis (TSP/HAM) associated with the T cell lymphotropic virus in type I humans (HTLV-1) is a slow, chronic, and progressive disease that causes balance changes. TSP/HAM diagnosis can be classified as probable, possible, and definite. We compared the static balance control of HTLV-1-infected patients with different TSP/HAM diagnosis. (2) Methods: Our sample consisted of 13 participants infected with HTLV-1 and 16 healthy participants. The center of pressure was recorded using a force platform with open and closed eyes. We divided the recordings into three intervals, period T1 (corresponds to the first 10 s); period T2 (from 10 to 45 s); period T3 (from 45 to 55 s). (3) Results: Eight participants infected with HTLV-1 were classified as probable TSP/HAM and five participants infected with HTLV-1 were classified as definite TSP/HAM. There was a significant increase in postural instability in patients with definite PET/MAH considering the structural and global variables of body sway compared to the control and the probable TSP/HAM. (4) Conclusions: We concluded that the severity of balance is directly related to the degree of signs and symptoms of TSP/HAM.

Postural Adjustments in HTLV-1 Infected Patients during a Self-Initiated Perturbation.

BACKGROUND: Human T-cell lymphotropic virus type 1 (HTLV-1) infection can be associated with tropical spastic paraparesis (TSP/HAM), which causes neurological myelopathy and sensory and muscle tone alterations, leading to gait and balance impairments. Once trunk perturbation is predicted, the motor control system uses anticipatory and compensatory mechanisms to maintain balance by recruiting postural muscles and displacement of the body's center of mass. METHODS: Twenty-six participants (control or infected) had lower limb muscle onset and center of pressure (COP) displacements assessed prior to perturbation and throughout the entire movement. RESULTS: Semitendinosus (ST) showed delayed onset in the infected group compared to the control group. The percentage of trials with detectable anticipatory postural adjustment was also lower in infected groups in the tibialis anterior and ST. In addition, COP displacement in the infected group was delayed, had a smaller amplitude, and took longer to reach the maximum displacement. CONCLUSIONS: HTLV-1 infected patients have less efficient anticipatory adjustments and greater difficulty recovering their postural control during the compensatory phase. Clinical assessment of this population should consider postural stability during rehabilitation programs.

Ganglion cells and displaced amacrine cells density in the retina of the collared peccary (Pecari tajacu).

In the present study, we investigated the topographical distribution of ganglion cells and displaced amacrine cells in the retina of the collared peccary (Pecari tajacu), a diurnal neotropical mammal of the suborder Suina (Order Artiodactyla) widely distributed across central and mainly South America. Retinas were prepared and processed following the Nissl staining method. The number and distribution of retinal ganglion cells and displaced amacrine cells were determined in six flat-mounted retinas from three animals. The average density of ganglion cells was 351.822 ± 31.434 GC/mm2. The peccary shows a well-developed visual streak. The average peak density was 6,767 GC/mm2 and located within the visual range and displaced temporally as an area temporalis. Displaced amacrine cells have an average density of 300 DAC/mm2, but the density was not homogeneous along the retina, closer to the center of the retina the number of cells decreases and when approaching the periphery the density increases, in addition, amacrine cells do not form retinal specialization like ganglion cells. Outside the area temporalis, amacrine cells reach up to 80% in the ganglion cell layer. However, in the region of the area temporalis, the proportion of amacrine cells drops to 32%. Thus, three retinal specializations were found in peccary's retina by ganglion cells: visual streak, area temporalis and dorsotemporal extension. The topography of the ganglion cells layer in the retina of the peccary resembles other species of Order Artiodactyla already described and is directly related to its evolutionary history and ecology of the species.

Influence of proprioceptive neuromuscular facilitation on the muscle tonus and amplitude of movement in HTLV-1-infected patients with HAM/TSP.

An HTLV-1-infected patient can develop paraparesis that limits their movements. Rehabilitation techniques could improve the motor abilities of these patients. The present study investigates five cases of physical therapy intervention in HTLV-1 patients to evaluate the influence of functional rehabilitation on the tonus and range of motion (ROM) of HTLV-1 patients with spasticity. The patients had a gain of ROM, especially in the lower limb, and reduction in hypertonia/spasticity after functional treatment. The reduction in hypertonia increased the ROM. Thus, functional methods may be valuable for the rehabilitation of HTLV-1 patients with neurological damage.

Influence of proprioceptive neuromuscular facilitation on the muscle tonus and amplitude of movement in HTLV-1-infected patients with HAM/TSP

Abstract An HTLV-1-infected patient can develop paraparesis that limits their movements. Rehabilitation techniques could improve the motor abilities of these patients. The present study investigates five cases of physical therapy intervention in HTLV-1 patients to evaluate the influence of functional rehabilitation on the tonus and range of motion (ROM) of HTLV-1 patients with spasticity. The patients had a gain of ROM, especially in the lower limb, and reduction in hypertonia/spasticity after functional treatment. The reduction in hypertonia increased the ROM. Thus, functional methods may be valuable for the rehabilitation of HTLV-1 patients with neurological damage.