Modern lifestyles often involve long periods of sitting, which can increase the risk of heart problems, obesity, and other health issues. Diet also plays a key role in heart health. Coffee and hibiscus tea are two common beverages, but their effects during prolonged sitting are not well understood.
This study will examine how drinking coffee versus hibiscus tea affects blood pressure, heart rate, and heart rate variability in men and women during extended periods of sitting.
Participants (30 in total: 15 women and 15 men) will take part in a randomized crossover study, meaning each person will try both beverages at different times. Data will be collected using questionnaires, body measurements, and devices to measure heart rate, blood pressure, and heart rate variability.
The goal is to better understand how these drinks influence heart health during sedentary behavior.
Age between 18 and 35 years.
Normal to elevated blood pressure (systolic <130 mmHg and diastolic <80 mmHg) and normal resting heart rate (60-100 bpm), ensuring selection of healthy adults and minimizing confounding factors.
Generally healthy, without chronic or acute medical conditions, to reduce external influences on study outcomes.
Physically inactive, not meeting current physical activity guidelines, as the study targets sedentary individuals.
Known allergy or hypersensitivity to hibiscus or coffee, as participants will consume these beverages during the study.
Current use of medications that could influence blood pressure, heart rate, or heart rate variability, including antihypertensive, chronotropic, or vasoactive drugs.
Any medical condition or health issue that may interfere with safe participation or affect study measurements.
Crossover
Coffee
Dietary supplementParticipants will consume 3 cups of Arabica coffee (Guatemalan origin), providing a total of 400 mg of caffeine. Each cup is prepared with 6% coffee grounds per 100 mL of water, brewed at 90°C for 6 minutes using an electric drip coffee maker, yielding 100.8 mg caffeine per 100 mL. Immediately following coffee consumption, participants will engage in uninterrupted sitting for 3 hours. Blood pressure, heart rate, and other study questionnaires will be measured at baseline (before coffee), 1 hour after coffee intake, and hourly during the 3-hour sitting period.
Hibiscus drink
Dietary supplementParticipants will consume 3 servings of hibiscus leaves tea per day, each serving containing 1.25 g of dried hibiscus leaves, totaling 3.75 g per session. The tea will be prepared by steeping the leaves in 240 mL of boiling water (100°C) for 10 minutes. Immediately after consuming the hibiscus tea, participants will engage in uninterrupted sitting for 3 hours. Blood pressure, heart rate, and other study questionnaires will be measured at baseline (before tea), 1 hour after tea intake, and hourly during the 3-hour sitting.
Systolic and diastolic blood pressure
Systolic and diastolic blood pressure will be assessed using an oscillometric blood pressure monitor (Omron HEM 7124 CP, Omron Healthcare, Illinois, USA). Measurements will be conducted in accordance with the guidelines of the American Heart Association (AHA) and the American College of Cardiology (ACC).
Heart Rate
Heart rate will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions. The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess heart rate (beat/minute)
NN Intervals
NN Intervals will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions. The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess NN Intervals (milliseconds)
RMSSD
RMSSD will be measured using the Polar V800 system, which consists of a wristwatch and a Bluetooth heart rate sensor. The sensor will be positioned on the participant's chest, just below the pectoral muscles. Participants will remain seated quietly for 10 minutes while continuous heart rate data are recorded according to the manufacturer's instructions. The clearest five-minute segment of the 10-minute recording will be analyzed using Kubios HRV Premium software to assess RMSSD (milliseconds squared)
Height
Height (cm) will be measured using an electronic stadiometer (Stadium Scale) with participants standing barefoot in an upright position. Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.
Weight
Body weight (kg) will be recorded using a calibrated digital scale (Seca). Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.
Body Mass Index
Body mass index (BMI) (kg/m2) will be calculated based on height and weight. Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.
Body Fat Percentage
Body fat percentage (%) will be assessed using a bioelectrical impedance analysis device (Tanita MC-980, Japan). Measurements will be performed under standardized conditions, with participants wearing light clothing and no shoes, to ensure accuracy and consistency.
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King Saud University
Lead sponsor
Princess Nourah Bint Abdulrahman University
Collaborator
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