Oxygen Uptake Kinetics During Submaximal Exercise in Adults With Down Syndrome
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Enrollment
- 28
- Locations
- 2
- Primary Endpoint
- Oxygen uptake kinetics
Study Overview
Brief Summary
This study aims to compare the rate at which oxygen uptake adapts to submaximal, moderate intensity exercise (oxygen uptake kinetics) between adults with and without Down syndrome, to determine the contribution of oxygen uptake kinetics to exercise intolerance of adults with Down syndrome. Additionally, the study will investigate the role of oxygen delivery (by the cardiovascular circuit) and oxygen utilization (in the mitochondria) on the oxygen uptake kinetics of adults with Down syndrome to identify specific areas which adults with Down syndrome could benefit from targeting during exercise training. Overall, this study aims to contribute to the knowledge on the exercise capacity of adults with Down syndrome, in order to improve the way adults with Down syndrome participate in and benefit from exercise.
Participants will perform a maximal exercise test on a treadmill, and walk on a treadmill at a submaximal, moderate intensity speed and incline, during which oxygen uptake at the lungs, cardiac output, and oxygen utilization in the muscle will be measured.
Detailed Description
Down syndrome (Ds) is the most common chromosomal disorder, affecting approximately 1 in every 800 live births in the US. In addition to a number of comorbidities, individuals with Ds have low cardiorespiratory fitness. Their low fitness cannot be explained by low levels of physical activity, lack of motivation, or lack of understanding of the test, but rather has a physiological cause. Autonomic dysfunction has been identified as one major contributor to the low cardiorespiratory fitness in individuals with Ds, but it does not fully explain the phenomenon.
Cardiorespiratory fitness is determined by the capacity of the body to produce energy, which largely relies on the ability to take up, deliver, and use oxygen. This process of oxygen transport is governed by the pulmonary, cardiovascular, and muscular system, and the degree to which they work together. At the start of exercise, these three systems respond in a delayed pattern, requiring the body to compensate energy production through anaerobic means, which negatively affect one's exercise tolerance. Thus, the quicker the adaptation of these three systems (i.e. the quicker their kinetics), the better one's ability to perform and tolerate exercise.
The rate of adaption of these oxygen transport system can be quantified by assessing oxygen uptake (pulmonary), cardiac output (cardiovascular), and mitochondrial oxygen utilization (muscle) kinetics, which all show a delayed, exponential increase towards steady state at the start of moderate intensity exercise. The kinetics of these three systems have never been assessed in individuals with Ds, and could provide valuable insights into their low cardiorespiratory fitness and reduced exercise tolerance.
The aim of this research proposal is therefore to determine the differences in kinetics of oxygen uptake, cardiac output, and mitochondrial oxygen utilization between individuals with and without Ds to better understand the underlying physiology and potentially improve healthy by using this knowledge for exercise interventions.
Overall aim: to better understand the relation between oxygen uptake kinetics and cardiorespiratory fitness in individuals with Ds.
Study Design
- Study Type
- Interventional
- Allocation
- Non Randomized
- Intervention Model
- Parallel
- Primary Purpose
- Screening
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to 35 Years (Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •low active (defined as being involved in less than 30 minutes of moderately-intense physical activity per day);
- •diagnosis with Down syndrome trisomy 21 (Down syndrome group only);
- •normal thyroid function or stable thyroid function (with medications) for at least 6 months (Down syndrome group only).
Exclusion Criteria
- •asthma or other pulmonary disease;
- •severe obesity (defined as BMI >40);
- •uncontrolled hypertension (defined as blood pressure >130/80 mmHg);
- •congenital heart disease;
- •diabetes (defined as Hba1c of >7.5% or use of glucose lowering medication);
- •current smoking;
- •pregnancy.
Outcomes
Primary Outcomes
Oxygen uptake kinetics
Time Frame: Through study completion, on average 4 hours
The finite rate at which oxygen uptake (measured with breath-by-breath gas exchange analysis at the mouth) adapts to a (submaximal) increase in exercise intensity, primarily captured by time constant tau, which describes the time needed to reach 63% of the required, steady state oxygen uptake
Secondary Outcomes
- Cardiac output kinetics(Through study completion, on average 4 hours)
- Ventilatory threshold (L/min)(Through study completion, on average 4 hours)
- Oxygen uptake efficiency slope(Through study completion, on average 4 hours)
- Heart rate(Through study completion, on average 4 hours)
- Relative peak oxygen uptake (corrected for total body mass)(Through study completion, on average 4 hours)
- Relative peak oxygen uptake (corrected for lean body mass)(Through study completion, on average 4 hours)
- Muscle deoxygenation kinetics(Through study completion, on average 4 hours)
- Absolute peak oxygen uptake(Through study completion, on average 4 hours)
- Ve/VCO2 slope(Through study completion, on average 4 hours)
- Steady-state cardiac output(Through study completion, on average 4 hours)
- Ventilatory threshold (%VO2peak)(Through study completion, on average 4 hours)
- Stroke volume(Through study completion, on average 4 hours)
- Lean body mass(Through study completion, on average 4 hours)
Investigators
Victor Beck
Graduate Research Assistant
University of Nevada, Las Vegas