Effects of 5-Minute Light-Intensity Physical Activity Breaks (Sit-Cycling and Stand-Twisting) on Cognitive Function, Sleepiness, and Back Pain in Physically Inactive University Students: Protocol for a Mixed-Design Laboratory Study.

Both 5-minute sit-cycling and stand-twisting bouts were verified to fall within the light-intensity physical activity range.

• The substudy measured oxygen uptake during 5-minute bouts of sit-cycling (S-C) and stand-twisting (S-T) in n=6 participants (27.3% of the main study sample).
• Both modalities produced metabolic equivalents (METs) of <3, meeting the operational definition of LIPA.
• This verification confirmed both modalities could be implemented as brief, standardized LIPA breaks in the main trial.

University students may remain sedentary for large parts of the day, spending more than 9 hours per day sitting.

• Prolonged sitting is associated with increased risk for adverse health outcomes in adulthood.
• Light-intensity physical activity (LIPA) can be integrated into university students' daily routines to counteract the negative effects of prolonged sitting on cognitive function and musculoskeletal health.

The study was designed as a mixed-design laboratory trial with both between-participant and within-participant factors.

• The main study comprised N=22 physically inactive university students, with a methodological substudy of n=6 (27.3%).
• Participants were allocated in a 1:1 ratio to either sit-cycling (S-C) or stand-twisting (S-T) as the between-participant factor.
• Each participant completed two laboratory visits within their assigned modality: an experimental LIPA visit and a modality-matched passive control visit (passive sitting), enabling within-person intervention-control comparisons.
• The passive control for S-C was passive sitting, and the passive control for S-T was also passive sitting, matched for equal duration.

The primary endpoint was defined as change in bilateral dorsolateral prefrontal cortex oxygenated hemoglobin from baseline to immediately after the intervention during cognitive task performance.

• The primary outcome measured bilateral dorsolateral prefrontal cortex (DLPFC) oxygenated hemoglobin (O2Hb) using functional near-infrared spectroscopy (fNIRS).
• The comparison was intervention versus control condition.
• Secondary outcomes included O2Hb persistence at 20 minutes postintervention, cognitive performance assessed via n-back test and Stroop Color and Word Test (SCWT), subjective sleepiness, and back pain.

The study was registered and conducted within a defined timeline with data collection completed in December 2024.

• The study was funded by the Sendai University International Collaborative Research Grant in April 2023.
• The trial was registered with ClinicalTrials.gov (NCT06703424) on November 21, 2024.
• Participant recruitment and data collection were completed in December 2024.
• Data cleaning and preliminary analyses were ongoing at the time of protocol publication, with outcomes anticipated to be reported in late 2026.
• The trial was conducted in Singapore.