Pressure pain sensitivity changes after use of shock-absorbing insoles among young soccer players training on artificial turf: a randomized controlled trial.

Study Design: Prospective, randomized, controlled single-blind intervention trial.
Objectives: Shock-absorbing insoles (SAIs), compared with usual insoles, were hypothesized to result in larger increases in pressure pain threshold (PPT) after 3 weeks of use.
Background: Shock-absorbing insoles can decrease self-reported pain among young soccer players training on artificial turf. However, nothing is known about the underlying changes in pain sensitivity assessed by PPT. Methods Seventy-five players were included from the youth teams of under 15, under 17, and under 19 years of age, playing for the Aalborg Boldspilklub (AaB) professional sports club. After a randomization stratified by team and age, players were divided into 2 groups, one that received SAIs and a control group that used their usual insoles. Assessments were made in both groups after 3 weeks of training on artificial turf (baseline) and 3 weeks later (follow-up). The primary outcome was change in PPTs from baseline to follow-up, with PPTs measured over 13 locations on the plantar surface of the foot, leg, and low back of the nonpreferred kicking leg.
Results: A significantly larger increase was found in PPTs from baseline to follow-up for the SAI group compared with the control group (mean difference, 62 kPa; 95% confidence interval [CI]: 40, 85 kPa). The PPTs increased significantly more among the SAI group compared with the control group (P<.05) for the abductor digiti minimi (mean difference, 82 kPa; 95% CI: 6, 157 kPa), tibialis anterior (mean difference, 125 kPa; 95% CI: 20, 230 kPa), medial gastrocnemius (mean difference, 83 kPa; 95% CI: -6, 171 kPa), and erector spinae (mean difference, 86 kPa; 95% CI: -17, 188 kPa).
Conclusion: The use of SAIs resulted in increased PPTs after 3 weeks of training on artificial turf compared with controls, suggesting a protective role of SAIs in pressure sensitivity and pain perception.