Variation in percentage weight bearing with changes in standing posture during water immersion: implication for clinical practice

Background: The degree of weightlessness during water immersion is usually estimated through percentage weight bearing (PWB). However, variations in PWB in different standing postures have not been documented. The study was designed to investigate the PWB of apparently healthy individuals in four standing postures at the anterior superior iliac spine level of immersion. Methods: One hundred and ninety-three consenting undergraduates were purposively enlisted in this study. Participants' body weight (BW) was measured on land as well as in Erect Standing (ES), Grasp-Inclined-Prone-Standing (GIPS), Half-Grasp-Inclined-Towards-Side Standing (HGITSS) and Inclined-Standing with Head Support (ISHS) postures in hydro pool, using a specially designed water-proof weighing scale. PWB was calculated by dividing BW in water by BW on land and multiplying by 100. Data were analyzed using mean, standard deviation and ANOVA at alpha = 0.05. Results: The mean age and BW (on land) of the participants were 22.4 years and 60.7 kg respectively. Participants' PWB were significantly different (p < 0.05) across the four standing postures. PWB was highest in ES and lowest in ISHS; PWB in ES (52.3 +/- 5.8) being significantly higher (p < 0.001) than that observed in the derived standing postures. Further, PWB in GIPS (43.3 +/- 5.6) and ISHS (43.2 +/- 7.3) were significantly lower than in HGITSS (47.4 +/- 5.2) posture while PWB in GIPS and ISHS postures were not significantly different (p > 0.05). Conclusion: Changes in standing posture have significant effect on PWB in hydro pool. The finding has implication for partial weight bearing exercises in hydro pool.