Balance in single-limb stance in healthy subjects – reliability of testing procedure and the effect of short-duration sub-maximal cycling

BACKGROUND: To assess balance in single-limb stance, center of pressure movements can be registered by stabilometry with force platforms. This can be used for evaluation of injuries to the lower extremities. It is important to ensure that the assessment tools we use in the clinical setting and in research have minimal measurement error. Previous studies have shown that the ability to maintain standing balance is decreased by fatiguing exercise. There is, however, a need for further studies regarding possible effects of general exercise on balance in single-limb stance. The aims of this study were: 1) to assess the test-retest reliability of balance variables measured in single-limb stance on a force platform, and 2) to study the effect of exercise on balance in single-limb stance, in healthy subjects. METHODS: Forty-two individuals were examined for test-retest reliability, and 24 individuals were tested before (pre-exercise) and after (post-exercise) short-duration, sub-maximal cycling. Amplitude and average speed of center of pressure movements were registered in the frontal and sagittal planes. Mean difference between test and retest with 95% confidence interval, the intraclass correlation coefficient, and the Bland and Altman graphs with limits of agreement, were used as statistical methods for assessing test-retest reliability. The paired t-test was used for comparisons between pre- and post-exercise measurements. RESULTS: No difference was found between test and retest. The intraclass correlation coefficients ranged from 0.79 to 0.95 in all stabilometric variables except one. The limits of agreement revealed that small changes in an individual's performance cannot be detected. Higher values were found after cycling in three of the eight stabilometric variables. CONCLUSIONS: The absence of systematic variation and the high ICC values, indicate that the test is reliable for distinguishing among groups of subjects. However, relatively large differences in an individual's balance performance would be required to confidently state that a change is real. The higher values found after cycling, indicate compensatory mechanisms intended to maintain balance, or a decreased ability to maintain balance. It is recommended that average speed and DEV 10; the variables showing the best reliability and effects of exercise, be used in future studies

Relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade em crianças

The aim of the present study were: 1) To verify the relationship of vertical, horizontal and sextuple jumps with agility and velocity of 5, 10 and 25 m; 2) To verify the capacity of these jumps to predict the agility and 5, 10 and 25 m velocity performance in children. Twenty eight boys (9.47 ± 0.64 years) and thirty girls (9.69 ± 0.70 years) were evaluated. The correlation values between agility and velocity on 5, 10 and 25 m velocity were, respectively, r = 0.63, 0.51, 0.44 and 0.64 with vertical jump, r = 0.68, 0.62, 0.28 and 0.62 with sextuple jump, and r = 0.60, 0.50, 0.26 and 0.57 with horizontal jump. The vertical and sextuple jumps were able to predict the agility and 25 m velocity performance (p < 0.05). Furthermore, they demonstrated capacity to predict 5 and 10 m velocity, respectively (p < 0.05). The vertical and sextuple jump tests may be used for assessment and control of training with children practicing activities that require agility and velocity, since both jumps predicted the agility and velocity performance, which did not occur with the horizontal jump.Os objetivos do presente estudo foram: 1) verifi car a relação dos saltos vertical, horizontal e sêxtuplo com a agilidade e velocidade de 5, 10 e 25 m; 2) verifi car a capacidade desses saltos em predizer o desempenho da agilidade e velocidade de 5, 10 e 25 m em crianças. Vinte e oito meninos (9,47 ± 0,64 anos) e 30 meninas (9,69 ± 0,70 anos) foram avaliados. Os valores de correlação entre a agilidade, velocidade de 5, 10 e 25 m foram, respectivamente, r = 0,63, 0,51, 0,44 e 0,64 com o salto vertical, r = 0,68, 0,62, 0,28 e 0,62 com o salto sêxtuplo, e r = 0,60, 0,50, 0,26 e 0,57 com o salto horizontal. O salto vertical e o salto sêxtuplo foram capazes de predizer o desempenho da agilidade e da velocidade de 25 m (p < 0,05). Além disso, demonstraram capacidade de predizer a velocidade de 5 e 10 m, respectivamente (p < 0,05). Os testes de salto vertical e sêxtuplo podem ser utilizados para avaliação e controle do treinamento com crianças praticantes de atividades que demandam agilidade e velocidade, uma vez que ambos os saltos predisseram o desempenho da agilidade e velocidade, o que não ocorreu com o salto horizontal