Abstract

The center of pressure (COP) on the feet is a crucial parameter providing information about structural and postural balance. A disturbance in this global pattern causes or reflects dysfunctions in the distribution of tension within the body. Postural disorders that manifest as an imbalance of the center of gravity in the sagittal plane lead to multisegmental ergonomic disturbances of the musculoskeletal system, resulting in compensations, pain, and, over time, structural overload changes and defects. Early detection of anterior-posterior load imbalances and their correction is of great importance for the prevention and treatment of musculoskeletal disorders.

Objective. To assess the impact of individually selected PORON heel lifts and lower limb correction in the transverse plane on body balance.

Methods. The study included 96 participants (n=100%), including 62 women (nf% = 64.58%) and 34 men (nm% = 35.42%), aged 15 to 80 years. The average weight of the participants was 75 kg (SD = 18.244), their average height was 1.705 m (SD = 0.093), and their average BMI was 24.81 (SD = 5.009). Exclusion criteria. Individuals diagnosed with significant foot and lower limb deformities or conditions significantly affecting body balance. A pedobarographic examination (EPS R2) was conducted while participants stood barefoot. Each test lasted 20 seconds, with a sampling rate of 1 ms (20,000 samples per test). The study included four trials: trial 0 in free standing, trial 1 with a 3 mm PORON heel lift, trial 2 with a 6 mm heel lift, and trial 3 in the lower limb correction test in the transverse plane (rotation).

Results. The study demonstrated a significant effect of using a low PORON offloading heel lift on balancing anterior-posterior pressure distribution on the feet.

The median heel underload in the control test (without correction) was −7.05% (interquartile range [−11.1%; −1.2%]). The greatest change was observed with the 6 mm heel lift (−3.0%; [−7.2%; +3.0%]). The Kruskal–Wallis statistical significance test for comparing all trials showed a significant difference (χ²[3] = 15.47, p=0.001). The Wilcoxon rank sum test, used to analyze statistical significance between individual trials, indicated a significant difference between trial 0 and trial 2 (p = 0.001) and between trial 0 and trial 3 (p = 0.036). The difference between trial 0 and trial 1 was nearly significant (p=0.054). The study found no significant effect of the interventions on lateral (right–left) pressure distribution (χ²[3] = 0.87, p = 0.834). Statistical analysis of 10 body balance parameters showed a significant difference between trials only in parameters describing body oscillations in the sagittal plane. The COP–barycenter angle of the feet significantly decreased (χ²[3] = 15.01, p=0.002), while the mean COP distance along the Y-axis significantly increased (χ²[3] = 10.01, p = 0.018).

Conclusions. For postural disorders that shift the center of gravity forward and affect balance in the sagittal plane, the use of PORON heel lifts is justified. Given that the PORON material used in the study is an offloading material with a hardness of approximately 15 Shore and that our applied interventions were significantly lower than those previously studied, these solutions reduce the undesired effects of heel elevation while increasing comfort and footwear compatibility.

Manual correction of the lower limb in the transverse plane also positively influences anterior–posterior COP balance, shifting weight distribution backward. The combination of heel offloading and correction of foot overpronation has a significant impact on relieving pressure on the forefoot, improving standing posture ergonomics, and promoting postural re-education from a forward-leaning position.

Statistical analysis. Statistical analyses were performed using the R statistical software, version 4.3.0 (The R Foundation for Statistical Computing, Wirtschaftsuniversität Wien, Vienna, Austria). Given the significant non-normality of variable distribution in the trials, the Kruskal–Wallis test was applied. The Wilcoxon rank sum test (also known as the Mann–Whitney–Wilcoxon test), with Bonferroni correction for multiple comparisons, was used to identify trial pairs where significant differences occurred. Results were considered statistically significant at p<0.05.

Key words

PORON heel lifts, postural balance, foot supination, anterior-posterior pressure