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

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. 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. 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, I = 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, I = 95%); rectus abdominis (RA) (MD -31.51, 95% CI -70.58, -3.57, I = 85%); tibialis anterior (TA) (MD -44.70, 95% CI -94.30, 4.91, I = 63%); soleus (SOL) (MD -37.74, 95% CI -65.43, -10.05, I = 91%); gastrocnemius (GAS) (MD -120.59, 95% CI -206.70, -34.49, I = 94%); quadriceps (Q) (MD -17.42, 95% CI -34.73, -0.12, I = 0%); biceps femoris (BF) (MD -117.47, 95% CI -192.55, -42.70, I = 97%); COP onset (MD -45.28, 95% CI -89.57, -0.98, I = 93%), and COP apa (COPapa) (MD 2.35, 95% CI -0.09, 4.79, I = 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. Older adult