No abstract

Single leg balance training promotes significant increments in balance control, but previous reviews on balance control have not analyzed this form of balance training. Accordingly, we aimed to review the single leg balance training literature to better understand the effects of applying this training to healthy individuals. We searched five databases—PubMed, EMBASE, Scopus, Lilacs, and Scielo—with the following inclusion criteria: (a) peer-reviewed articles published in English; (b) analysis of adult participants who had no musculoskeletal injuries or diseases that might impair balance control; and (c) use of methods containing at least a pre-test, exclusive single leg balance training, and a post-test assessment. We included 13 articles meeting these criteria and found that single leg balance training protocols were effective in inducing balance control gains in either single- or multiple-session training and with or without progression of difficulty. Balance control gains were achieved with different amounts of training, ranging from a single short session of 10 minutes to multiple sessions totaling as much as 390 min of unipedal balance time. Generalization of balance gains to untrained tasks and cross-education between legs from single leg balance training were consistent across studies. We concluded that single leg balance training can be used in various contexts to improve balance performance in healthy individuals. These results extend knowledge of expected outcomes from this form of training and aid single leg balance exercise prescription regarding volume, frequency, and potential progressions.

Generation of automatic postural responses (APRs) scaled to magnitude of unanticipated postural perturbations is required to recover upright body stability. In the current experiment, we aimed to evaluate the effect of previous postural perturbations on APR scaling under conditions in which the current perturbation is equal to or different from the previous perturbation load inducing unanticipated forward body sway. We hypothesized that the APR is scaled from the association of the current perturbation magnitude and postural responses to preceding perturbations. Evaluation was made by comparing postural responses in the contexts of progressive increasing versus decreasing magnitudes of perturbation loads. Perturbation was applied by unanticipatedly releasing a cable pulling the body backwards, with loads corresponding to 6%, 8% and 10% of body mass. We found that the increasing as compared to the decreasing load sequence led to lower values of (a) displacement and (b) velocity of center of pressure, and of activation rate of the muscle gastrocnemius medialis across loads. Muscular activation onset latency decreased as a function increasing loads, but no significant effects of load sequence were found. These results lead to the conclusion that APRs to unanticipated perturbations are scaled from the association of somatosensory feedback signaling balance instability with feedforward control from postural responses to previous perturbations.

Following unpredictable large-magnitude stance perturbations diverse patterns of arm and leg movements are performed to recover balance stability. Stability of these compensatory movements could be properly estimated through qualitative evaluation. In the present study, we present a scale for evaluation of compensatory arm and leg movements (CALM) in response to unpredictable displacements of the support base in the mediolateral direction. We tested the CALM scale for intra- and inter-rater reliability, correlation with kinematics of arm and leg movement amplitudes, and sensitivity to mode (rotation, translation and combined) and magnitude (velocity) of support base displacements, and also to perturbation-based balance training. Results showed significant intra- and inter-rater coefficients of agreement, ranging from moderate (0.46–0.53) for inter-rater reliability in the arm and global scores, to very high (0.87–0.99) for inter-rater leg scores and all intra-rater scores. Analysis showed significant correlation values between scale scores and the respective movement amplitudes both for arm and leg movements. Assessment of sensitivity revealed that the scale discriminated the responses between perturbation modes, platform velocities, in addition to higher balance recovery stability as a result of perturbation-based balance training. As a conclusion, the CALM scale was shown to provide adequate integrative evaluation of compensatory arm and leg movements for balance recovery stability after challenging stance perturbations, with potential application in fall risk prediction.