Heat Therapy and Muscle Function Study

January 27, 2021 updated by: Jayson Gifford, Brigham Young University

Improving Critical Power and Muscle Function in Older Adults With Heat Therapy

Exercise tolerance decreases with age and a sedentary lifestyle. Muscle critical power (CP), is a sensitive measure of exercise tolerance that is more even more relevant to and predictive of endurance performance than VO2max.

While recent evidence indicates that CP and muscle function decrease with aging, the cause of this decrease in CP and the best way to mitigate the decrease in CP are unknown.

This study will:

  1. Measure knee extensor CP in young and old individuals and determine the extent to which changes in muscle oxygen delivery (e.g. resistance artery function, maximum exercise blood flow), muscle mass and composition (e.g. whole-muscle size, muscle fiber cross-sectional area) and mitochondrial oxygen consumption (e.g. maximal coupled respiration of permeabilized fibers biopsied from the knee extensors) contribute to the decrease in CP with age.
  2. Examine the effectiveness of two different therapies (1. High Intensity Interval Training, HIIT and 2. Muscle Heat Therapy) at improving muscle function and critical power in young and older adults.
  3. Examine the impact of muscle disuse (2 weeks of leg immobilization), a potential contributor to the decrease in muscle function with aging, on muscle function and critical power and determine if heat therapy is an effective means of minimizing the impact of disuse on muscle function and critical power.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Anticipated)

148

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • United States
    • Utah
      • Provo, Utah, United States, 84602
        • Recruiting
        • Brigham Young University
        • Contact:
        • Contact:
        • Principal Investigator:
          • Jayson Gifford, Ph.D.
        • Principal Investigator:
          • Robert Hyldahl, Ph.D.
        • Principal Investigator:
          • Chad Hancock, Ph.D.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 95 years (ADULT, OLDER_ADULT)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • 18-95 years of age
  • Currently no cardiovascular or metabolic disease (e.g. heart failure, diabetes)
  • ability to perform knee extension exercise

Exclusion Criteria:

  • Pregnant
  • Current cardiovascular or metabolic disease (e.g. heart failure, diabetes)
  • participating in exercise training within the last 6 months
  • inability to perform knee extension exercise

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: TREATMENT
  • Allocation: RANDOMIZED
  • Interventional Model: PARALLEL
  • Masking: SINGLE

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
EXPERIMENTAL: Effect of High Intensity Interval Training

Young and older subjects will participate in single-leg, high-intensity interval training of the right knee extensors (4 intervals of 4 minutes at 80% of max aerobic power with 4 minute rest intervals between, 3x per week for 6 weeks).

Muscle function and knee extensor critical power will be measured before and after the 6 weeks of treatment.
Other: High Intensity Interval Training of the Knee Extensors

Subjects will perform intense, single leg knee extension exercise 3 times a week for 6 weeks. Specifically, subjects will be seated in a custom knee extension ergometer and perform single leg, dynamic knee extension (similar to single leg cycling) as they perform the exercise. After a 6 minute warm-up at ~20% of that leg's maximum aerobic power (determined during a graded exercise test of single leg knee extension), subjects will perform 4 bouts of 4 minutes at ~80% of maximum aerobic power. Recovery of 4 minutes at ~40% will occur between each bout of exercise. A cool down will be provided at the end of exercise. In total, subjects will perform 40 minutes of single leg knee extension exercise, 3 times a week for 6 weeks.

Maximum aerobic power (determined by a graded exercise test) will be determined again at 3 weeks to appropriately adjust the training intensity.

Other Names:
  • HIIT
EXPERIMENTAL: Effect of Muscle Heat Therapy

Young and older subjects will participate in single-leg,heat therapy training of a single leg ( quadriceps femoris, 120 minutes of shortwave diathermy to raise the muscle temperature to ~39C) 3 times a week for 6 weeks.

Muscle function and knee extensor critical power will be measured before and after the 6 weeks of treatment.
Other: Muscle Heat Therapy
Subjects will receive muscle heat therapy on the knee extensor muscles (short-wave diathermy) for 120 minutes for each visit. Specifically, subjects will lie supine while short-wave diathermy units (Megapulse II) will be placed on the quadriceps femoris and turned on to 800 pulses per second with a pulse duration of 400 microseconds. Our previous research (e.g. Hafen et al 2018- Repeated exposure to heat stress...) has indicated that this treatment raises muscle temperature to ~39C, a similar temperature induced by exercise.
Other Names:
  • Short-wave Diathermy
SHAM_COMPARATOR: Effect of Sham Muscle Heat Therapy

Young and older subjects will participate in a sham treatment of single-leg,heat therapy training of the right knee extensors (120 minutes with shortwave diathermy unit positioned on leg, but not turned on) 3 times a week for 6 weeks.

Muscle function and knee extensor critical power will be measured before and after the 6 weeks of treatment.
Other: Sham Heat Therapy
Specifically, subjects randomly assigned to the sham group will receive the same treatment as the heat group (same number of visits and set up with the heating units applied to leg for 2 hours each visit) except, unbeknownst to either group, the heating units will never be turned on for the sham group.
SHAM_COMPARATOR: Effect of Immobilization with Daily Sham Heat Therapy

Young subjects (18-35 years) will undergo 2 weeks of leg immobilization while receiving 2 hours of a sham heat therapy treatment each day. For the sham treatment, the heating device will be applied to the limb, but, unbeknownst to the participant, it will not be turned on.

Muscle function and knee extensor critical power will be measured before and after the 2 weeks of leg immobilization.
Other: Sham Heat Therapy
Specifically, subjects randomly assigned to the sham group will receive the same treatment as the heat group (same number of visits and set up with the heating units applied to leg for 2 hours each visit) except, unbeknownst to either group, the heating units will never be turned on for the sham group.
EXPERIMENTAL: Effect of Immobilization with Daily Heat Therapy

Young subjects (18-35 years) will undergo 2 weeks of leg immobilization while receiving 2 hours of heat therapy treatment each day. Heat therapy will consist of 120 minutes of shortwave diathermy to raise the quadriceps femoris muscle temperature to ~39C.

Muscle function and knee extensor critical power will be measured before and after the 2 weeks of leg immobilization.
Other: Muscle Disuse
Subjects will undergo 2 weeks of limb immobilization (a model of muscle disuse). Specifically, a knee brace will be placed on one of the subjects' legs and bent to a flexion of 60 degrees to prevent the foot from touching the ground while standing. Subjects will given a pair of crutches and asked to ambulate on crutches for 2 weeks, avoiding bearing any weight with the immobilized leg.
Other Names:
  • Leg Immobilization

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Muscle Critical Power
Time Frame: 3-8 weeks

Muscle exercise tolerance, quantified as critical power, will be assessed before and after each intervention. The main outcome will be the change in critical power, expressed in Watts, elicited by each intervention.

Specifically, participants will perform 3-5 different power outputs of single leg knee extension exercise as long as they can. Subsequently, the line of best fit between the total work performed and duration of each power output trial will be used to quantify critical power, expressed in Watts.
3-8 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Resistance Artery Function
Time Frame: 3-8 weeks

Resistance Artery Function will be assessed with the Passive Leg Movement (PLM) technique before and after each intervention. The main variable of interest will be the change in peak blood flow elicited by PLM from before to after each intervention.

Specifically, PLM will be performed with a member of the research team moving a subject's knee joint through a 90 degree range of motion, at a rate of 1 Hz for 60 seconds. This passive movement elicits a hyperemic response that will will be quantified with Doppler ultrasound of the femoral artery and expressed in ml/min. The highest 1-second average of blood flow to occur during the movement will be identified as the peak blood flow response.

The main variable of interest will be the change in peak blood flow elicited by PLM from before to after each intervention.
3-8 weeks
Maximum Exercise Blood Flow
Time Frame: 3-8 weeks

The maximum rate of blood flow achieved during exercise will be determined before and after each intervention. The main variable of interest will be the change in maximum exercise blood flow from before to after each intervention, expressed in ml/min.

Specifically, exercise blood flow will be assessed by quantifying the peak hyperemic response, expressed in ml/min, to active single leg knee extension exercise. Following a warm-up, subjects will perform maximal single leg knee extension exercise for 3 minutes while blood flow is quantified with Doppler ultrasound (Logiq E, GE) of the femoral artery. The average rate of blood flow achieved during the final 30 seconds of the exercise will be identified as the maximum exercise blood flow, expressed in ml/min.
3-8 weeks
Muscle Fiber Size
Time Frame: 3-8 weeks

The cross-sectional area of muscle fibers biopsied from the treated vastus lateralis will be used to quantify the size of muscle size before and after each intervention. The main variable of interest will be the change in average myofiber cross-sectional area, expressed in square micrometers, from before to after each intervention.

Specifically, muscle biopsy samples will be mounted on a cork in tragacanth gum . Frozen samples will be adhered to a microscope slide for staining. Slides will be incubated with fluorescently labeled antibodies. CSA will be quantified for each fiber using Olympus CellSens software and subsequently averaged for all fibers on the slide.
3-8 weeks
Muscle Mitochondrial Function
Time Frame: 3-8 weeks

Muscle mitochondrial function will be measured in permeabilized fibers biopsied from the vastus lateralis before and after each intervention.

Specifically, maximal coupled respiration (i.e. OXPHOS or State 3) will be measured with a clark-type electrode (O2K, Oroboros) and expressed in picomoles of oxygen consumed per second.

The main variable of interest will be the change in Maximal Couple Respiration from before to after each intervention.
3-8 weeks
Vastus Lateralis Cross-Sectional Area
Time Frame: 3-8 weeks

The cross-sectional area of the treated vastus lateralis will be measured with magnetic resonance imaging before and after each intervention. The main variable of interest will be the change in cross-sectional area, expressed in square centimeters, from before to after each intervention.

Specifically, MRI will be used to assess whole muscle cross sectional area of the vastus lateralis. Participants will be scanned while laying supine in a 3.0 Tesla MRI scanner (Siemens). A stock Siemens 2-D multi-slice gradient-recalled echo (GRE) MRI pulse sequence will be used. Images will be takin in slices every 5mm, resulting in a total sequence time of approximately 2-min. This will provide cross-sectional images of the vastus lateralis from the base of the femur (distal condyles) up to the groin. .
3-8 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Brigham Young University

Investigators

  • Study Director: Jayson Gifford, Ph.D., Brigham Young University
  • Principal Investigator: Robert Hyldahl, Ph.D., Brigham Young Univeristy

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (ANTICIPATED)

April 1, 2021

Primary Completion (ANTICIPATED)

December 31, 2024

Study Completion (ANTICIPATED)

December 31, 2024

Study Registration Dates

First Submitted

October 14, 2020

First Submitted That Met QC Criteria

January 27, 2021

First Posted (ACTUAL)

February 2, 2021

Study Record Updates

Last Update Posted (ACTUAL)

February 2, 2021

Last Update Submitted That Met QC Criteria

January 27, 2021

Last Verified

January 1, 2021

More Information

Terms related to this study

Other Study ID Numbers

  • F2020-023

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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