Perturbation-based balance training leads to improved reactive postural responses in individuals with Parkinson's disease and freezing of gait.

Perturbation-based balance training (PBT) exposes individuals to a series of sudden upright balance perturbations to improve their reactive postural responses. In this study, we aimed to evaluate the effect of a short PBT program on body balance recovery following a perturbation in individuals with freezing of gait due to Parkinson's disease. Volunteers (mean age = 64 years, SD = 10.6) were pseudorandomly assigned either to a PBT (n = 9) or to a resistance training (RT, n = 10) group. PBT was implemented through balance perturbations varying in the kind, direction, side and magnitude of support base displacements. Both groups exercised with progressive difficulty/load activities twice a week for 4 weeks. Specific gains and generalization to dual-tasking and faster-than-trained support base displacements were evaluated 24 h after the end of the training, and retention was evaluated after 30 days of no training. Results showed that, compared with RT, PBT led to more stable postural responses in the 30-day retention evaluation, as indicated by decreased CoP displacement, velocity and time to direction reversal and reduced numbers of near-falls. We found no transfer either to a dual task or to a higher perturbation velocity. In conclusion, a training program based on diverse unpredictable balance perturbations improved the stability of reactive postural responses to those perturbations suffered during the training, without generalization to more challenging tasks.

High contextual interference in perturbation-based balance training leads to persistent and generalizable stability gains of compensatory limb movements.

Reactive responses to balance perturbations have been shown to be improved by training. This investigation aimed to compare the effects of block and random training perturbation schedules on stability gains of compensatory arm and leg movements in response to unpredictable large-magnitude balance perturbations. Perturbations were produced by means of sudden displacements of the support base, associating mode (rotation, translation, combined), direction, and velocity of platform motion. Healthy young participants were assigned to one of three groups: random, block, and control. For the random group, perturbation sequence was unpredictable. For the block group, each balance perturbation was repeated over blocks of four trials. Controls were tested only, serving as reference of first trial responses in the post-test. Evaluation was made through a scale rating stability of compensatory arm and leg movements (CALM). We probed immediate and persistence gains (1-week retention), in addition to generalizability to perturbations of higher velocity and to dual-tasking (mental subtraction). In the post-test both the block and random groups achieved higher leg and global scores in comparison with controls in the most challenging perturbations. In retention and transfer tests, results for the global score indicated higher values for the random than for the block and control groups. These results support the conclusion that high but not low contextual interference in perturbation-based balance training leads to enduring and generalizable increased stability gains of compensatory limb movements in response to unpredictable balance perturbations.

Evaluation of balance recovery stability from unpredictable perturbations through the compensatory arm and leg movements (CALM) scale.

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.

Effect of association of imagery and physical practice on children's motor learning / Efeito da associação de prática imagética e física na aprendizagem motora em crianças

Imagery training has been shown to induce motor learning in adults, but similar evidence in children is scarce. In this experiment, we aimed to evaluate the effect of association between imagery and physical practice compared to pure physical practice in the learning of a manual task in 9-10 year-old children. The task consisted of transporting a block and fitting it into a support with speed and steadiness, assessing movement time to complete the "reaching" and "transport" task components. The children were assigned to one of three groups: (a) physical practice (PHYS) (240 trials), (b) combination (COMB) of imagery (180 trials) and physical (60 trials) practice, and (c) control (CON), associating visual rotation (180 trials) and physical practice (60 trials). Performance was evaluated immediately and 24 h after practice. Results indicated that the PHYS group achieved a persistent performance gain in the "transport", but not in the "reaching" task component, while the COMB group achieved persistent performance gains in both movement components; no significant differences were found for the CON group. Our results suggest that imagery training improves the task mental representation in children, while physical practice provides sensory feedback on the performed movements. As a conclusion, the results suggest that combination of imagery and physical practice can be more effective than pure physical practice for children's motor learning.

Imagética dos próprios movimentos tem mostrado induzir aprendizagem motora em adultos, porém são escassas evidências similares em crianças. O objetivo deste experimento foi avaliar o efeito da associação entre prática imagética e prática física em comparação com prática física pura em uma habilidade manual em crianças de 9-10 anos de idade. A tarefa consistiu em transportar um bloco e encaixá-lo em um suporte com rapidez e estabilidade, avaliando-se o tempo de movimento para completar os componentes de "alcance" e "transporte". As crianças foram distribuídas em três grupos: (a) prática física (FIS) (240 tentativas), (b) combinação (COMB) de prática imagética (180 tentativas) e prática física (60 tentativas), e (c) controle (CON), com associação de rotação visual (180 tentativas) e prática física (60 tentativas). O desempenho foi avaliado imediatamente e 24 h após a prática. Os resultados indicaram que o grupo FIS obteve ganho persistente de desempenho no componente "transporte", porém não no componente "alcance", enquanto o grupo COMB alcançou ganho persistente de desempenho em ambos os componentes de movimento; não foram encontradas diferenças significantes para o grupo CON. Estes resultados sugerem que a prática imagética aprimora a representação mental da tarefa motora em crianças, enquanto que a prática física oferece informação de feedback sensorial sobre o os movimentos realizados. Como conclusão, nossos resultados sugerem que a combinação de prática física e imagética é um procedimento que pode ser mais efetivo do que prática física pura para aprendizagem motora em crianças.