An investigation of trunk movement during reaching in children

Investigators: Ms Kate Carroll, Prof Mary Galea, Dr Noel Lythgo

The Functional Reach (FRT) and Lateral Reach (LRT) Tests are measures of dynamic balance used by physiotherapists in the clinical setting. However, little is known about how the movement is actually performed in the paediatric population, in particular the contribution of trunk movement to the reach. This descriptive study used 3-D movement analysis to identify common patterns of movement in these tests and their age-related changes.

Forty-five able-bodied subjects from the following age groups were recruited: 4-5 years (n=10), 6-7 years (n=9), 9-10 years (n=9), 18-22 years (n=13). Three children with cerebral palsy (CP) were also recruited. Each subject performed four tests: the FRT and LRT, as well as the seated versions of these tests (sitFRT and sitLRT). Reflective markers were attached at the shoulder girdle, pelvic girdle, elbows, wrists, ankles and feet, using a model of marker placement that created a triangular plane of markers at both shoulder and pelvic girdles. The movements were videotaped and digitized using the Peak Motus system. Custom designed software in Java was then used to calculate flexion, lateral flexion and rotation angles, thereby yielding data describing trunk movement. The trials were time-normalised using Igor Pro.

All tests show increasing reach with increasing age. The FRT and LRT show a reduction in movement variability with increasing age. The trajectory of the reaching arm closely mirrors upper trunk movement for all tests. Pelvis flexion (for FRT/sitFRT) and pelvis lateral flexion (for LRT/sitLRT) are the key movement elements in these tasks. In the sit LRT, adults demonstrate a reduction in trunk rotation, trunk righting, and use of counterbalancing movements with other limbs compared to distance reached. The best explanation of this is that adults appear to have more trunk stability and strength than children. The children with CP appear to show different patterns of movement and are not able to reach as far as their able-bodied peers in the FRT and LRT (Fig. 2).

Figure 2 .
The wrist marker trajectory (bold line = mean; dotted lines indicate one standard deviation) in the 4-5 year old age group of able-bodied children. The blue line shows the wrist trajectory in a child with CP

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