Resistance Exercise-induced Anabolism in Youths and Adults

August 14, 2024 updated by: Bareket Falk, Brock University

Resistance exercise training (RET) in children and adolescents has become a popular area of research, with a growing body of evidence supporting its use. Position and consensus statements about RET for children indicate that it is safe and effective at increasing muscular strength, improving sport performance, and mitigating injury risk. Neural and muscular mechanisms can improve muscle strength following RET. Neural factors include improved recruitment and firing of an individual's motor units, and muscular factors primarily include an increase in the size of the muscle (hypertrophy).

In children, little is known about how these mechanisms relate to muscle strength. There is very little evidence of morphological changes following RET in children. Therefore, conventional wisdom is that children rely only on neural factors to improve strength following RET. Nevertheless, some studies have suggested RET-induced muscle hypertrophy in children and adolescents, indicating that with certain training protocols, children may achieve muscle growth.

Hypertrophy of muscle fibres occurs when the rate of muscle protein synthesis (MPS) is greater than the rate of protein breakdown, and is enhanced with the ingestion of dietary amino acids. Due to ethical concerns with obtaining muscle samples (i.e., from muscle biopsies) in pediatric populations, MPS rates have not been previously assessed following RET in children. Recent advancements in stable-isotope methodology (specifically, leucine) allow for the estimation of MPS in a non-invasive breath test.

The objective of the proposed research is to examine the effects of an acute bout of RET on leucine retention (a proxy for MPS) in children, adolescents, and adults using a non-invasive breath test.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Resistance exercise training (RET) in children and adolescents has become a popular area of research, with a growing body of evidence supporting its use. Position and consensus statements about RET for children indicate that it is safe and effective at increasing muscular strength, improving sport performance, and mitigating injury risk. Neural and muscular mechanisms can improve muscle strength following RET. Neural factors include improved recruitment and firing of an individual's motor units, and muscular factors primarily include an increase in the size of the muscle (hypertrophy).

In children, little is known about how these mechanisms relate to muscle strength. There is very little evidence of morphological changes following RET in children. Therefore, conventional wisdom is that children rely only on neural factors to improve strength following RET, possibly due to their lower levels of circulating androgens. Nevertheless, some studies have suggested RET-induced muscle hypertrophy in children and adolescents, indicating that with certain training protocols, children may achieve muscle growth.

Hypertrophy of muscle fibres occurs when the rate of muscle protein synthesis (MPS) is greater than the rate of protein breakdown, and is enhanced with the ingestion of dietary amino acids. Due to ethical concerns with obtaining muscle samples (i.e., from muscle biopsies) in pediatric populations, MPS rates have not been previously assessed following RET in children. Recent advancements in stable-isotope methodology allow for the estimation of MPS in a non-invasive breath test, which is based on the retention of an essential amino acid (i.e., leucine) that is preferentially metabolized within skeletal muscle. Given that amino acids can only be 'stored' in functional body proteins with any excess being converted to energy (i.e., oxidized), this non-invasive technique is ideal to safely estimate the anabolic (i.e., growth) potential of RET in children. Indeed, similar techniques using ingested stable isotopes have been safely and successfully used in children and adolescents.

The objective of the proposed research is to examine the effects of an acute bout of RET on leucine retention (a proxy for MPS) in children, adolescents, and adults using a non-invasive breath test. It is hypothesized that following a bout of RET, protein retention will be augmented in all groups compared to a non-exercised condition. However, due to a greater basal rate of leucine retention (i.e., for growth processes), the RET-induced increase will be relatively lower in the children and adolescents.

Design: The proposed study will use a cross-sectional design that will compare leucine retention at rest, as well as following a bout of resistance exercise in children, adolescents, and adults.

Procedures: Participants will be required to make three visits to the Applied Physiology Laboratory at Brock University for the completion of all procedures.

During visit 1, the participants and their guardian(s) (if under the age of 18) will be informed of all tests and procedures that will take place over the duration of the study. Written and verbal consent will be obtained from the participants and their guardians (in the case of children and adolescents) before proceeding with further questionnaires. Questionnaires screening for medical concerns, pubertal stage, athletic training practices, menarche and oral contraceptive use (for adolescent and adult females), habitual eating habits, and habitual physical activity will then be completed. Anthropometric measurements will also be performed (i.e., height, seated height, body fat composition, skinfold thickness, limb lengths, limb circumferences, muscle cross sectional area). Following questionnaires and anthropometric measurements, participants will be familiarized with the exercises to be performed in their RET session. Each participant's strength will also be tested for these exercises.

Visits 2 and 3 will serve as the experimental sessions and will consist of a RET and a rest session, done in a counterbalanced order. For these sessions, participants will arrive fasted in the morning, and will be provided with a standardized breakfast and beverage. At the beginning of the experimental sessions, participants will have their breath collected. This will be followed by RET in one of the sessions, or continued rest. A dose of L-[1-13C]leucine isotope will then be consumed based on each participant's body mass (within a protein and carbohydrate beverage) and the breath of each participant will continue to be collected for the next 5 hours (total of 11 breath samples). A small snack will be given to each participant during this breath collection period.

Resistance Exercise: Strength testing and the training protocol will involve the following exercises which will all be performed using strength training machines. The use of such equipment is considered safer than the use of free weights as there are less degrees of freedom during limb movements, preventing technical failure prior to muscular fatigue. The following exercises will be performed: seated leg press, seated overhead press, seated chest press, seated horizontal row. Exercises will be performed with techniques described by the Canadian Society for Exercise Physiology (CSEP - PATH, 2021).

The RET protocol will comprise of 3-5 sets of each exercise at 70-80% of 1RM. Each exercise will be performed until failure (i.e., until the participant can no longer complete the movement with safe technique), as this has been shown to be optimal for stimulating MPS and eliciting muscle hypertrophy. Approximately 8-15 repetitions are expected to be completed per set and ~90s of rest will be given between sets. A similar acute RET protocol has previously been shown to be a sufficient stimulus to elicit differences in leucine retention compared to rest (tested using the non-invasive breath test that will be used in the proposed study) in adults.

The participants in the proposed study will be male and female prepubertal children (~7-12 years), adolescents (~13-16 years), and adults (18-35 years).

Study Type

Interventional

Enrollment (Estimated)

60

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

  • Name: Bareket Falk, PhD
  • Phone Number: 4979 905-688-5550
  • Email: bfalk@brocku.ca

Study Contact Backup

  • Name: Andrew McKiel, MSc
  • Phone Number: 5826 905-688-5550
  • Email: am20ff@brocku.ca

Study Locations

  • Canada
    • Ontario
      • St. Catharines, Ontario, Canada, L2S3A1
        • Recruiting
        • Brock University
        • Contact:
          • Bareket Falk, PhD

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

  • Child
  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • healthy
  • free of injury that would prevent resistance exercise

Exclusion Criteria:

  • consumed any medications in the past year which may affect muscle function
  • had an injury in the past 6 months that would limit the movements required for the protocols
  • been told that has diabetes
  • been told that had a heart problem
  • been told that have a breathing problem (e.g., asthma)
  • been told that sometimes experience seizures
  • had joint instability or ongoing join chronic pain
  • been told that had kidney problems
  • had stomach problems such as ulcers
  • experience prolonged bleeding after a cut

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: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Protein supplementation
Other: exercise
Resistance exercise

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Leucine retention
Time Frame: During the experimental session, expired air is collected pre-ingestion and every 30minutes. i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes.
retention is calculated as intake minus leucine in expired air (mg). This test involves blowing into a breath collection bag before, and every ~30 minutes after (for ~300 minutes) ingesting a powdered-amino acid supplement (modeled after egg protein - the WHO/FAO gold standard protein source) mixed with water. The supplement will contain 0.25 g/kg body mass of protein as crystalline amino acids, 0.75 g/kg body mass of carbohydrate (~4kcal/kg of body mass), and will be enriched with 1 mg/kg of L-[1-13C]leucine (Cambridge Isotope Laboratories Inc., Tewksbury, MA, USA), which is a stable isotope that can be detected in the breath of the participants when not used for protein synthesis. The amount of the isotope that is expelled (oxidized) in the breath of the participant can be detected using continuous-flow isotope ratio mass spectrometry (ID-Microbreath; Compact Science Systems, Newcastle, UK), which allows for the estimation of leucine retention (intake - oxidation)
During the experimental session, expired air is collected pre-ingestion and every 30minutes. i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
body mass
Time Frame: baseline in each experimental session
mass in kg
baseline in each experimental session
body height
Time Frame: baseline, pre-intervention
height in cm
baseline, pre-intervention
arm circumference
Time Frame: baseline in each experimental session
arm circumference in cm
baseline in each experimental session
thigh circumference
Time Frame: baseline in each experimental session
circumference in cm
baseline in each experimental session
Skinfold thickness - triceps
Time Frame: baseline, pre-intervention
skinfold thickness in mm (using Harpenden calipers)
baseline, pre-intervention
skinfold thickness - subscapula
Time Frame: baseline, pre-intervention
skinfold thickness in mm (using Harpenden calipers)
baseline, pre-intervention
Body composition (BIA)
Time Frame: baseline, pre-intervention
Bioelectrical impedance analysis (BIA) - percentage of body fat
baseline, pre-intervention
Muscle thickness - thigh, upper arm
Time Frame: baseline, pre-intervention
muscle thickness in mm - using ultrasound system
baseline, pre-intervention
[13C]leucine in urine
Time Frame: baseline and post-each experimental session. i.e., at -60 and 300 minutes
concentration in microgram, using mass spectrometry
baseline and post-each experimental session. i.e., at -60 and 300 minutes
maximal strength (1RM)
Time Frame: baseline, pre-intervention
maximal weight lifted/pushed in kg - seated leg press, seated overhead press, seated chest press, seated horizontal row
baseline, pre-intervention
oxygen consumption
Time Frame: During the experimental session, every 30 minutes: i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes.
Oxygen consumption (l/min) - using open circuit metabolic system
During the experimental session, every 30 minutes: i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes.
carbon dioxide production
Time Frame: During the experimental session, every 30 minutes: i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes. (every 30min)
carbon dioxide production (l/min) - using open circuit metabolic system
During the experimental session, every 30 minutes: i.e., at -60, 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300 minutes. (every 30min)
nutritional intake
Time Frame: baseline, pre-intervention
Nutritional intake (carbohydrates, fats, proteins) - in g/day and as % or daily recommendation. Using Food Frequency questionnaire and 24-h recall.
baseline, pre-intervention
leisure time physical activity level
Time Frame: baseline, pre-intervention
physical activity level, using the Godin-Shephard leisure time questionnaire. Minimum score is 0, with no maximum limit. Higher score reflects more physical activity
baseline, pre-intervention
Pubertal stage (children and adolescents only)
Time Frame: baseline, pre-intervention
Based on secondary sex characteristics of pubertal hair (Tanner scale). Stages are 1-5, where 1 is pre-pubertal and 5 is post-pubertal
baseline, pre-intervention

Collaborators and Investigators

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

Sponsor

Brock University

Collaborators

University of Toronto

Investigators

  • Principal Investigator: Bareket Falk, PhD, Brock University

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 (Estimated)

September 1, 2024

Primary Completion (Estimated)

August 1, 2025

Study Completion (Estimated)

September 1, 2025

Study Registration Dates

First Submitted

December 28, 2023

First Submitted That Met QC Criteria

February 11, 2024

First Posted (Actual)

February 13, 2024

Study Record Updates

Last Update Posted (Actual)

August 16, 2024

Last Update Submitted That Met QC Criteria

August 14, 2024

Last Verified

August 1, 2024

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • BFalk

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Data will only be available to researchers directed involved in the study

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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