The effect of a placebo on strength performance in children

Abstract

Background and study aim. Placebo responses are a well-known psychophysiological phenomenon observed in various areas of human performance. In the context of physical activity, these responses can influence motivation, perceived exertion, and measurable motor outcomes in both adults and children. Although placebo strategies are used in different practical settings, their relative effectiveness in enhancing strength performance in children remains a subject of practical interest. This study examined the impact of placebo administration on strength-related outcomes in children. Materials and Methods. Ninety-two participants (mean age 10.4 years) were randomly assigned to a placebo group (n = 47) or a control group (n = 45). The placebo group received a sweet-tasting liquid accompanied by a verbal suggestion of performance enhancement. Performance was assessed using a pull-up hold, handgrip strength, a wall-sit hold, and the standing broad jump. Results. Within-group analyses showed improvements in both groups for the pull-up hold (Control: p = 0.044, d = 0.39; Placebo: p < 0.001, d = 0.42). Only the placebo group showed significant gains in right-hand grip strength (+2.8 kg, p < 0.001, d = 0.73), left-hand grip strength (+2.0 kg, p < 0.001, d = 0.57), and the wall-sit hold (+21.3 s, p = 0.001, d = 0.52). Between-group comparisons showed significant advantages for the placebo group in right-hand grip strength (p < 0.001, d = 0.79) and in the standing broad jump (p = 0.008, d = 0.58). There were no significant differences in the other outcomes. Conclusions. The findings indicate that placebo interventions in children may preferentially enhance strength-endurance tasks, with less consistent effects on explosive performance. The improvement in handgrip strength, particularly in the right hand, suggests that placebo mechanisms may also influence measures of maximal strength.