The Effects of Interrupting Periods of Prolonged Sitting by Acute Physical Activity with Different Densities on Cognitive Outcomes: A Randomized-Crossover Trial in University Students

INTERVENTION: Group 1: Low‐Density Physical Activity Participants will watch a non‐arousing documentary for 90 minutes while seated. The sitting period will be interrupted by three 5‐minute bouts of cycling on a cycle ergometer at moderate intensity. The cycling bouts will take place at approximately 20, 50, and 80 minutes after the beginning of the 90‐minute period. Participants will exercise at moderate intensity (approximately 46–63% of VO2ma Xor 64–76% of HRmax). Heart rate will be monitored throughout the exercise bouts using a heart rate monitor. Group 2: High‐Density Physical Activity Participants will watch a non‐arousing documentary for 90 minutes while seated. The sitting period will be interrupted by three 5‐minute bouts of cycling on a cycle ergometer at moderate intensity. The cycling bouts will take place at approximately 50, 65, and 80 minutes after the beginning of the 90‐minute period Group 3: Passive Control Participants will remain seated for 90 minutes while watching a non‐arousing documentary. No physical activity breaks will be performed during the 90‐minute sitting period. CONDITION: Healthy participants PRIMARY OUTCOME: The primary outcome is executive function performance. It is assessed at the beginning and end of each experimental condition using computerized cognitive tests of working memory (Corsi Block‐Tapping Test) and inhibitory control (Stroop Test). For the Corsi Block‐Tapping Test, the highest memory span is used as the performance indicator. For the Stroop Test, reaction time, accuracy, and the interference score (difference in reaction time and accuracy between congruent and incongruent trials) are used as performance indicators. The study is conducted using a randomized, controlled cross‐over design with three experimental conditions: uninterrupted sitting while watching a 90‐minute documentary, and two conditions in which the 90‐minute sitting period is interrupted by three 5‐minute bouts of moderate‐intensity cycling, differing in exercise density. SECONDARY OUTCOME: The secondary outcome is the change in serum brain‐derived neurotrophic factor (BDNF) concentration. BDNF is assessed at the beginning and end of each experimental condition by collecting approximately 10 mL of venous blood from the antecubital region. Blood samples are collected in EDTA tubes, centrifuged for 10 minutes at 4 °C and 2,000 rpm to obtain serum, and stored at ‐80 °C until further analysis. In addition, potential influencing factors are assessed at the beginning and end of each condition using questionnaires. Motivation, concentration, and mental fatigue are assessed using visual analogue scales ranging from 0 to 100, and sleepiness is quantified using the Karolinska Sleepiness Sca INCLUSION CRITERIA: Participants must meet all of the following INCLUSION CRITERIA: (1) young adults aged 18 to 30 years; (2) absence of acute and chronic diseases or health conditions that could interfere with study participation; and (3) low risk of adverse health effects in response to physical activity, assessed through a personal interview and established screening questionnaires, including the Physical Activity Readiness Questionnaire and the Beck Depression Inventory‐II.