The aim of this pilot study was to examine the impact of a brief physical activity intervention on adolescents’ subjective sleep quality. Cross-sectional studies indicate that physically active adolescents have better subjective sleep quality than those with more sedentary habits. However, less is known about the effectiveness of physical activity interventions in improving adolescents’ subjective sleep quality.

In a three-week physical activity intervention, four Icelandic upper secondary schools were randomized to either an intervention group with pedometers and step diaries or a control group without pedometers and diaries. Out of 84, a total of 53 students, aged 15–16 years, provided complete data or a minimum of two days step data (out of three possible) as well as sleep quality measures at baseline and follow-up. Subjective sleep quality, the primary outcome in this study, was assessed with four individual items: sleep onset latency, nightly awakenings, general sleep quality, and sleep sufficiency. Daily steps were assessed with Yamax CW-701 pedometers.

The intervention group (n = 26) had significantly higher average step-count (p = 0.03, partial ² = 0.093) compared to the control group (n = 27) at follow-up. Subjective sleep quality improved (p = 0.02, partial ² = 0.203) over time in the intervention group but not in the control group.

Brief physical activity interventions based on pedometers and step diaries may be effective in improving adolescents’ subjective sleep quality. This has important public health relevance as the intervention can easily be disseminated and incorporated into school curricula.