Dynamic Balance in Children With Trisomy 21: A Pilot Study

David Catela, Ana Paula Seabra Higher School of Sports Sciences of Rio Maior, Polytechnique Institute of Santarém, Santarém, Portugal Life Quality Research Centre (CIEQV), Rio Maior, Portugal Research Unity of the Polytechnique Institute of Santarém, Santarém, Portugal Bernardo Matias, Miguel Nunes, Pedro Neves, Samuel Rodrigues Higher School of Sports Sciences of Rio Maior, Polytechnique Institute of Santarém, Santarém, Portugal


Introduction 
Dynamic balance is the maintenance of equilibrium in rapidly changing kinetic condition during a motor action, being an essential component in many fundamental motor skills (DeOreo & Keogh, 1980;Espenschade & Eckert, 1980), particularly for pre-schoolers (B. D. Ulrich & D. A. Ulrich, 1985). Between three and six years of age, they increase the mastery of the base of support (Assaiante, Amblard, & Carblanc, 1988;Brenière, Bril, & Fontaine, 1989;Bril, & Breniere, 1988;Gallahue & Ozmun, 1998), the stabilization of the head in space (Assaiante & Amblard, 1993), and the use of peripheral vision (Assaiante, 1998); with the emergence of new modes of postural synergies (Shumway-Cook & Woollacott, 1985a). This contributes to an attunement of the vestibular-ocular reflex (Casselbrant et al., 2010)  information (Foudriat, Di Fabio, & Anderson, 1993). In studies on dynamic balance control, postural instability is created by action on the child or the support base (Shumway-Cook & Woollacott, 1985a;Forssberg & Nashner, 1982;Woollacott, Debû, & Mowatt, 1987); or, observing sustained, undisturbed spontaneous locomotor control (Valente, 2007), especially in the laboratory setting and in translational displacement; rotational conditions only those by extrinsic constraints (e.g., Amblard, Assaiante, Lekhel, & Marchand, 1994). Few tests run through rotations; for example, Zimmer and Volkamer (1987) include in their MOT 4-6 a test in which the child makes a 180° vertical jump to land on a rim in front of him/her, performing a second jump to starting position with another 180° rotation. Franco et al. (2017) based on solitary functional play, which is common in day care and preschool children (Rubin, Watson, & Jambor, 1978) asked children from three and six years old to spin on their selves until they cannot get more, noticing that 3-year-olds were slower, and that both directions of rotation were equally distributed among all children. At age 5, Down 21 children have a cumulative delay in motor development of approximately two years (Butterworth & Cicchetti, 1978;Share & French, 1974). Its ability to respond to loss of balance is very slow until age 6, probably not due to its hypotonia (Shumway-Cook & Woollacott, 1985b). Down's syndrome children are hardly able to ride a tricycle at age 7 (Share, 1971). However, three and six years old that performed jumping practice could improve their dynamic balance (Wang & Ju, 2002).
It was intended to verify if children with trisomy 21 had a similar performance to younger typically developing children, in a playful motor action.

Procedures and Protocols
According to Franco et al. (2017), it was asked to children to spin around themselves till they could not more or till they stopped definitively and totally unbalanced or fall on the floor, on a gym mat. The activity was presented was a playing one. No restriction of velocity or time was imposed. No feedback was provided. Participants did not receive any reward. It was allowed for child to stop for short moments during the spinning and to continue to spin, a behaviour that was frequent in children with trisomy 21. Direction of rotation, total spinning time, number of turns, and mean time per turn were obtained.

Statistical Analysis
It was used IBM SPSS Statistics for Windows, version 24, for a significance level of 0.05. Normal distribution was obtained through Shapiro-Wilk test. For comparison between groups, Mann-Whitney U test (Z), with Monte Carlo test, was used, and effect size r was estimated when significant difference occurred. Probability error was set at 0.05, two-tailed.

Results
On average, AD rotated less, for less time, spending more time per rotation, but without significant difference (Table 1) Of the DA, one third fell and rose to continue spinning; one third stopped and restarted spinning (at intervals of 2.05 ± 0.86s). Three AD performed the action counter clockwise and the other three clockwise.

Discussion
In this fundamental motor skill, these AD children retain slight but not significant limitation of motor performance. The occurrence of falls during activity may be due to their difficulty in efficiently using vestibular somatosensory information (Foudriat et al., 1993) and to readjust to situations of loss of stability (Shumway-Cook & Woollacott, 1985b), unlike children DT (cf. Franco et al., 2017). As in children with TD (Franco et al., 2017), in these AD children there is no evidence of predominance of direction of rotation.

Conclusion
The results support the hypothesis that AD can perform the spinning activity on itself, with (significantly) younger DTs, enabling during the motor action to AD momentary pauses and conditions for their physical safety.