Heat Therapy and Muscle Function Study

Not Applicable

Recruiting

• Conditions: Exercise Intolerance; Aging; Heat Therapy; High Intensity Interval Training
• Interventions: Other: Sham Heat Therapy; Other: Muscle Disuse; Other: Muscle Heat Therapy; Other: High Intensity Interval Training of the Knee Extensors

• Registration Number: NCT04733287
• Lead Sponsor: Brigham Young University

Brief Summary

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2020-10-14
• Status Verified: 2021-01
• Study First Submitted QC: 2021-01-27
• Last Update Submitted: 2021-01-27
• Study First Posted: 2021-02-02
• Last Update Posted: 2021-02-02
• Study Start: 2021-04-01
• Primary Completion: 2024-12-31
• Study Completion: 2024-12-31

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 148

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 & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Effect of Sham Muscle Heat Therapy	Sham 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.
Effect of Immobilization with Daily Heat Therapy	Muscle Disuse	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.
Effect of Immobilization with Daily Sham Heat Therapy	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.
Effect of Muscle Heat Therapy	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.
Effect of High Intensity Interval Training	High Intensity Interval Training of the Knee Extensors	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.

Primary Outcome Measures

Name	Time	Method
Muscle Critical Power	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.

Secondary Outcome Measures

Name	Time	Method
Muscle Fiber Size	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.
Muscle Mitochondrial Function	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.
Resistance Artery Function	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.
Maximum Exercise Blood Flow	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.
Vastus Lateralis Cross-Sectional Area	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. .

Trial Locations

Locations (1)

Brigham Young University; 🇺🇸 Provo, Utah, United States