Resistance Exercise-induced Anabolism in Youths and Adults
Trial Snapshot
- Phase
- Not Applicable
- Status
- Recruiting
- Sponsor
- Brock University
- Enrollment
- 60
- Locations
- 2
- Primary Endpoint
- Leucine retention
Study Overview
Brief Summary
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.
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.
Study Design
- Study Type
- Interventional
- Allocation
- Na
- Intervention Model
- Single Group
- Primary Purpose
- Basic Science
- Masking
- None
Eligibility Criteria
- Ages
- 7 Years to 35 Years (Child, Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •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
Outcomes
Primary Outcomes
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)
Secondary Outcomes
- body mass(baseline in each experimental session)
- Skinfold thickness - triceps(baseline, pre-intervention)
- Muscle thickness - thigh, upper arm(baseline, pre-intervention)
- maximal strength (1RM)(baseline, pre-intervention)
- body height(baseline, pre-intervention)
- arm circumference(baseline in each experimental session)
- thigh circumference(baseline in each experimental session)
- Pubertal stage (children and adolescents only)(baseline, pre-intervention)
- nutritional intake(baseline, pre-intervention)
- leisure time physical activity level(baseline, pre-intervention)
- Body composition (BIA)(baseline, pre-intervention)
- [13C]leucine in urine(baseline and post-each experimental session. i.e., at -60 and 300 minutes)
- skinfold thickness - subscapula(baseline, pre-intervention)
- oxygen consumption(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(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))
Investigators
Bareket Falk
Professor
Brock University