This study will examine whether very short bouts of stair climbing performed throughout the day can improve blood sugar control and cardiovascular health in adults with prediabetes. Participants will complete three separate study visits in random order: uninterrupted sitting, sitting interrupted by 3-minute light walking breaks each hour, and sitting interrupted by brief stair-climbing exercise "snacks" each hour.
During each visit, the research team will measure glucose, insulin, blood lipids, markers of inflammation and oxidative stress, and blood-vessel function. Continuous glucose monitors, blood samples, heart-rate and blood-pressure measurements, vascular ultrasound, and questionnaires will be used to assess the participants' responses.
The goal of the study is to determine whether brief stair-climbing breaks may be a practical way to reduce the negative effects of prolonged sitting and improve metabolic health in adults with prediabetes.
HbA1c 5.7% to 6.4%;
fasting plasma glucose 100 to 125 mg/dL; or
2-hour plasma glucose 140 to 199 mg/dL during a 75-g oral glucose tolerance test.
None
Crossover
Hourly 3-Minute Light Walking Breaks
BehavioralParticipants will interrupt prolonged sitting with a 3-minute light walking break at approximately 30, 90, 150, 210, 270, and 330 minutes during the approximately 6-hour experimental visit. Activity breaks are therefore separated by approximately 60 minutes. Participants will otherwise remain seated except as required for study procedures.
Hourly Stair-Climbing Exercise Snacks
BehavioralParticipants will interrupt prolonged sitting with brief stair-climbing exercise snacks at approximately 30, 90, 150, 210, 270, and 330 minutes during the approximately 6-hour experimental visit. During each bout, participants will ascend approximately three flights of stairs at a fast but safe self-selected pace for about 20 seconds. Participants will not run or skip steps, and use of the handrail will be permitted as needed.
6-Hour Postprandial Glucose Area Under the Curve (AUC)
Plasma glucose will be measured from a fasting venous blood sample obtained before Meal 1 and from serial venous blood samples collected every 30 minutes through 360 minutes after Meal 1 completion. Meal 1 completion will define the start of the postprandial period, and a second standardized meal will be provided at approximately 180 minutes. Plasma glucose AUC will be calculated across the 6-hour experimental period and compared among uninterrupted sitting, hourly 3-minute light walking breaks, and hourly stair-climbing exercise snacks.
6-Hour Postprandial Plasma Insulin Area Under the Curve (AUC)
Plasma insulin will be measured from a fasting venous blood sample obtained before Meal 1 and from prespecified serial venous blood samples collected through 360 minutes after Meal 1 completion. Meal 1 completion will define time 0, and a second standardized meal will be provided at approximately 180 minutes. Insulin AUC will be calculated across the 0- to 360-minute experimental period and compared among uninterrupted sitting, hourly 3-minute light walking breaks, and hourly stair-climbing exercise snacks.
6-Hour Postprandial Plasma Free Fatty Acid Response
Plasma free fatty acids will be measured from prespecified serial venous blood samples collected during each experimental visit. A fasting baseline sample will be obtained before Meal 1, followed by postprandial sampling through 360 minutes after Meal 1. Free fatty acid responses across the postprandial period will be compared among uninterrupted sitting, hourly 3-minute light walking breaks, and hourly stair-climbing exercise snacks.
6-Hour Postprandial Plasma Triglyceride Response
Plasma triglycerides will be measured from prespecified serial venous blood samples collected during each experimental visit. A fasting baseline sample will be obtained before Meal 1, followed by postprandial sampling through 360 minutes after Meal 1. Triglyceride responses across the postprandial period will be compared among the three experimental conditions.
Postprandial Plasma Malondialdehyde (MDA)
Plasma malondialdehyde (MDA), a marker of oxidative stress, will be measured from prespecified venous blood samples collected during each experimental visit. A fasting baseline sample will be obtained before Meal 1, with postprandial assessment through 360 minutes after Meal 1. MDA responses will be compared among uninterrupted sitting, hourly 3-minute light walking breaks, and hourly stair-climbing exercise snacks.
Postprandial Plasma Inflammatory Cytokines (TNF-α and IL-6)
Plasma tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) will be measured from prespecified venous blood samples collected during each experimental visit. A fasting baseline sample will be obtained before Meal 1, with postprandial assessment through 360 minutes after Meal 1. TNF-α and IL-6 responses will be compared among uninterrupted sitting, hourly 3-minute light walking breaks, and hourly stair-climbing exercise snacks.
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