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NCT Number: NCT06937164

Blood Pressure Following Isometric Exercise in Inactive Adults

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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Key information

Age range

18 year–55 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Canterbury Christ Church University

Canterbury, Kent, CT1 1QU, United Kingdom

Location status: Recruiting

Location contact

Sean Machak

CONTACT

[email protected]

+447864658805

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age 18 years or older
  • Self-reported physically inactive or insufficiently active (not meeting current physical activity guidelines)
  • Not currently engaged in structured resistance or isometric exercise training
  • Able to attend lab sessions over a 4-week period
  • Provides written informed consent

Exclusion criteria

  • Current diagnosis of hypertension requiring medication
  • Any known cardiovascular, neurological, or musculoskeletal condition contraindicating isometric exercise
  • Formal education or professional background in exercise science, physiology, or a related field
  • Pregnant or planning to become pregnant during the study period
  • Inability to follow verbal instructions or complete study protocols

Treatment and study plan

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.

Other names: Static Strength Training, Leg Extension Hold Training

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.

Primary outcomes

  1. Change in Resting Systolic Blood Pressure

    Time frame: Baseline to Post-Intervention (approximately 4 weeks)

    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.

Secondary outcomes

  1. Change in Diastolic Blood Pressure

    Time frame: Baseline to Post-Intervention (approximately 4 weeks)

    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.

  2. Post-Exercise Hypotension Response

    Time frame: During the first week of the exercise intervention. Sessions 1, 2 and 3.

    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.

  3. Change in Heart Rate Variability (HRV)

    Time frame: Baseline to Post-Intervention (approximately 4 weeks)

    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.

  4. Change in Muscle Fatigue Markers (EMG)

    Time frame: Baseline to Post-Intervention (Approximately 4 weeks)

    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.

Study contacts

Contact information is provided by the study sponsor or research team.

Philip Hurst

CONTACT

[email protected]

+44 (0)1227 927700 ext. 1466

Sean Machak

CONTACT

[email protected]

+447864658805

Sponsors and collaborators

Lead sponsor

Canterbury Christ Church University

Other

Registry information

Official study title

Beliefs and Expectation Effects on Blood Pressure Following Isometric Exercise in Inactive Adults

Acronym: BELIEF-BP

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Apr 22, 2025
Registry last updated
May 16, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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