Neck Static Stretching Acutely Reduces Blood Pressure Through Reduction of Tissue Stiffness

Investigators measured blood pressure while participants were sitting. A reliable blood pressure machine was used. Participants sat and rested for 5-10 minutes to let their blood pressure settle. The cuff was placed on the bare upper arm, about 2 centimeters above the inside of the elbow, with the arm supported at heart level. During the measurement, participants were asked to sit still, stay relaxed, and not talk. Data will be shown as means with standard deviations. To compare baseline values between SS and CC, investigators will first use paired t-tests. Invesigators will then check the data distribution and apply a repeated measures analysis of variance (two conditions × two time points) to look at the effects of time and condition. In the presence of a significant time × condition interaction, post hoc analyses with Scheffé correction will be conducted to locate the differences. Effect sizes will be calculated and reported as partial eta squared (η²p).

MAP was extrapolated from blood pressure using the following formula: MAP = DP + 1/3(SP - DP). Data will be shown as means with standard deviations. To compare baseline values between SS and CC, investigators will first use paired t-tests. Invesigators will then check the data distribution and apply a repeated measures analysis of variance (two conditions × two time points) to look at the effects of time and condition. In the presence of a significant time × condition interaction, post hoc analyses with Scheffé correction will be conducted to locate the differences. Effect sizes will be calculated and reported as partial eta squared (η²p).

Tissue stiffness was measured with a small handheld device (NEUTONE TDM-N1, TRY-ALL Corp., Japan). This device gently pressed into the skin with a fixed pressure to see how deep it could go. The bone at the base of the neck (C7) was used as a reference point. Measurements were taken on both sides of this bone, 2 centimeters to the right and left. Participants lay face down on a medical bed and were asked to stay completely relaxed. Data will be shown as means with standard deviations. To compare baseline values between SS and CC, investigators will first use paired t-tests. Invesigators will then check the data distribution and apply a repeated measures analysis of variance (two conditions × two time points) to look at the effects of time and condition. In the presence of a significant time × condition interaction, post hoc analyses with Scheffé correction will be conducted to locate the differences. Effect sizes will be calculated and reported as partial eta squared (η²p).

Heart rate (HR) and heart rate variability (HRV) were measured with a Polar H10 chest strap sensor, a device known to give accurate results. To prepare, participants were asked not to drink coffee or alcohol, avoid hard exercise for 24 hours, and keep their normal sleep routine. The tests were always done at the same time of day in both conditions (SS and CC) to avoid daily rhythm effects. Participants lay on their back and rested for 5 minutes before the test. Then, HR and HRV were recorded for another 5 minutes while they breathed normally. The chest strap was placed just below the chest bone and secured around the chest. Once the signal was ready, data were sent automatically to a mobile app (Elite HRV). HRV shows how much the time between heartbeats changes. Average HR was calculated from the same recordings. All data were later analyzed with special software (Kubios HRV). The same approach proposed for the other outcomes will be used for data analysis.