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.
Combat sports are characterized by frequent large-scale stance perturbations that may lead to falls. In the present investigation, we compared compensatory arm and leg movements in response to unpredictable stance perturbations between judokas and other athletes whose sports present reduced balance demand, relative to combat sports. Specifically, we tested judokas ( n = 9), and a group of swimmers and runners ( n = 11, controls) in sudden support base displacements in the mediolateral direction, generated by a movable electronic platform, in the following modes: (a) rotation, (b) translation, and (c) combined rotation-translation. The platform was displaced to either side, in three peak velocities (cm/second or o/second) of 20 (low), 30 (moderate), or 40 (high), resulting in 18 distinct perturbations. We evaluated postural responses with a scale for analyzing the stability of compensatory arm and leg movements (CALM). Results showed that, in the most challenging perturbations, judokas had higher stability scores (arm, leg, and global) than did the comparison group. Higher scores for judokas reflected their increased rate of motionless arm and leg responses and absence of near-falls, compared to 30% falls in the most challenging perturbations for the swimmers and runners. As a practical application, judo training may help achieve stable compensatory limb movements in a way that parallels the benefits obtained from perturbation-based balance training in laboratory settings.
No abstract
The scale for evaluation of compensatory arm and leg movements (CALM) was developed to evaluate balance stability recovery after unpredictable displacements of the support base in the mediolateral direction. The mediolateral perturbations are applied in three modes: rotation, translation or combined rotation-translation, to either side, in three platform peak velocities: 20º-20 cm/s (low), 30º-30cm/s (intermediate) or 0º-40 cm/s (high), keeping peak acceleration of 500 o /s 2 (cm/s 2 ) and displacement amplitude of 7 o (cm) constant across perturbations. The factors perturbation mode (3), direction (2) and velocity (3) of platform displacement are combined to generate 18 distinct stance perturbations. To create the context of unpredictability, perturbations are pseudorandomly sequenced. To become aware of the stance perturbations, participants watch a video demonstrating a person responding to the different platform perturbations included in the protocol. After video watching, subjects are warmed up for 5 min. with global movements. Initial feet positions are marked on the support base with adhesive tapes (5-cm width). Other adhesive tape marks are fixed 15 cm away from the outer border of the feet to either side, in parallel to the feet orientation. The initial participant's posture on the platform is keeping the Romberg's stance, with the feet oriented forward, touching each other, maintaining both arms relaxed hanging beside the trunk, and palms of the hands lightly touching the upper legs. Participants wear a safety harness supported by two ropes tied at the shoulders height with the other end attached overhead. The participant's aim across perturbations is to recover balance after support base displacements trying to maintain the initial body posture. Participants' responses are filmed from behind using a commercial digital camera (Sony), for off-line analysis based on the CALM scale.
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