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This study investigates how isometric exercise training (IET) affects blood pressure in physically inactive adults. Isometric exercise involves sustained muscle contractions without movement-for example, pushing against a fixed object. Previous research has shown that IET may help reduce blood pressure, but the mechanisms involved are not fully understood.
The purpose of this study is to assess both the immediate (acute) and long-term (chronic) effects of IET on cardiovascular outcomes. Participants will complete a series of lab-based exercise sessions over several weeks. In these sessions, they will perform repeated bouts of isometric leg extensions while seated on an exercise machine designed to measure muscle force.
Throughout the study, researchers will monitor participants' blood pressure, heart rate, and muscle activity. Acute responses-such as post-exercise hypotension (a short-term drop in blood pressure)-will be measured immediately after exercise. Chronic changes, such as resting blood pressure improvements, will be evaluated across the training period.
Additional measurements will include heart rate variability (HRV), which gives insight into autonomic nervous system activity, and electromyography (EMG), which tracks muscle fatigue and activation patterns. These data will help explore potential mechanisms behind the cardiovascular benefits of IET.
By examining how repeated sessions of isometric exercise influence blood pressure and related physiological responses, this research may support the use of IET as a non-pharmacological strategy for managing or preventing hypertension in physically inactive individuals.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Neutral Information + Isometric Exercise | Experimental | Participants in this group complete repeated isometric exercise training sessions. Prior to training, they receive a neutral informational presentation about isometric exercise, which does not mention blood pressure or cardiovascular benefits. The exercise consists of bilateral isometric leg extensions on a dynamometer. Cardiovascular and neuromuscular outcomes, including blood pressure, heart rate variability, and muscle fatigue, are monitored throughout the intervention period. |
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| Expectation-Enhancing Info + Isometric Exercise | Experimental | Participants in this group complete repeated isometric exercise training sessions. Prior to training, they receive an expectation-enhancing informational presentation that emphasizes the effectiveness of isometric exercise as a non-pharmacological intervention for reducing blood pressure. The exercise consists of bilateral isometric leg extensions on a dynamometer. Blood pressure, heart rate variability, and muscle activity are assessed to determine physiological responses to the intervention. |
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| No-Intervention Control | No Intervention | Participants in this group do not receive any intervention or educational presentation. They attend study visits for assessment purposes only. Measurements include resting blood pressure, heart rate variability, and muscle activity, allowing for comparison with the intervention groups to evaluate the effects of isometric exercise training. |
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Isometric Exercise Training (IET) | Behavioral | Participants perform four repetitions of 90 degree bilateral isometric leg extensions on a dynamometer at 30% of their maximum voluntary contraction (MVC). Each contraction is held for 2 minutes, with 2-minute rest intervals between bouts. Sessions are performed three times per week for four weeks. This behavioral intervention is designed to investigate the acute and chronic effects of isometric exercise on blood pressure, heart rate variability, and muscle fatigue. |
| Measure | Description | Time Frame |
|---|---|---|
| Change in Resting Systolic Blood Pressure | Systolic blood pressure will be measured at rest using a Task Force Monitor prior to and after the isometric exercise intervention period. The primary outcome is the change in resting systolic blood pressure from baseline to final testing. Measurements are taken in a seated position following standard resting protocols. | Baseline to Post-Intervention (approximately 4 weeks) |
| Measure | Description | Time Frame |
|---|---|---|
| Change in Diastolic Blood Pressure | Diastolic blood pressure will be assessed in the same manner as systolic. The secondary outcome is the change in diastolic values from baseline to final testing. | Baseline to Post-Intervention (approximately 4 weeks) |
| Post-Exercise Hypotension Response |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Sean Machak | Contact | +447864658805 | s.machak2125@canterbury.ac.uk | |
| Philip Hurst | Contact | +44 (0)1227 927700 | 1466 | philip.hurst@canterbury.ac.uk |
| Name | Affiliation | Role |
|---|---|---|
| Sean Machak | Canterbury Christ Church University | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Canterbury Christ Church University | Recruiting | Canterbury | Kent | CT1 1QU | United Kingdom |
This is an early-phase investigator-led study involving a small sample size. At this stage, there are no plans to share individual participant data due to ethical and data governance constraints outlined in the approved protocol. Aggregated results may be shared through publication or presentation.
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| ID | Term |
|---|---|
| D006973 | Hypertension |
| D057774 | Post-Exercise Hypotension |
| D057185 | Sedentary Behavior |
| ID | Term |
|---|---|
| D014652 | Vascular Diseases |
| D002318 | Cardiovascular Diseases |
| D054971 | Orthostatic Intolerance |
| D054969 | Primary Dysautonomias |
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Participants are randomly assigned to one of three parallel groups: (1) isometric exercise training (IET) with neutral information, (2) IET with expectation-enhancing information, or (3) a no-intervention control group. Intervention groups complete repeated isometric leg extension sessions across multiple visits. Prior to training, participants receive distinct information to influence their beliefs about IET. The control group does not receive training or information. Participants are blinded to group assignment, and outcomes such as blood pressure, heart rate variability, and muscle fatigue are assessed independently across groups.
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Participants are blinded to group assignment. They are not informed whether they are receiving neutral or expectation-enhancing information, or whether they are in a control group. Due to the nature of the study, the researcher is not blinded.
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| Expectation-Enhancing Informational Framing | Behavioral | Participants receive a brief standardized presentation highlighting isometric exercise as an evidence-based intervention for lowering blood pressure. The presentation includes statements designed to enhance outcome expectations based on prior literature and expert framing. |
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Post-exercise hypotension will be evaluated as the change in systolic and diastolic blood pressure immediately following each isometric exercise session, compared to pre-exercise baseline. |
| During the first week of the exercise intervention. Sessions 1, 2 and 3. |
| Change in Heart Rate Variability (HRV) | HRV will be analyzed using Task Force Monitor data to assess autonomic modulation. Measures include time-domain (e.g., RMSSD) and frequency-domain (e.g., LF/HF ratio) indices. | Baseline to Post-Intervention (approximately 4 weeks) |
| Change in Muscle Fatigue Markers (EMG) | Muscle fatigue will be assessed using surface electromyography (EMG) of the vastus lateralis. Fatigue indices include changes in median frequency and torque stability over repeated contractions. | Baseline to Post-Intervention (Approximately 4 weeks) |
| D001342 | Autonomic Nervous System Diseases |
| D009422 | Nervous System Diseases |
| D007022 | Hypotension |
| D001519 | Behavior |