The Potential of a Low Oxygen Environmental Chamber as an Aid to Exercise Training to Improve Metabolic Health
Condition: Overweight; Physical Inactivity; Healthy
MeSH terms: Overweight
Study type: Interventional

Summary: 
      Obesity is a major global health issue and a primary risk factor for metabolic-related
      disorders. While physical inactivity is one of the main contributors to obesity, it is a
      modifiable risk factor with exercise training as an established, non-pharmacological
      treatment to prevent the onset of metabolic-related disorders, including obesity. Exposure to
      hypoxia via normobaric hypoxia (simulated altitude via reduced inspired oxygen fraction),
      termed hypoxic conditioning, in combination with exercise has been increasingly shown in the
      last decade to enhance blood glucose regulation and decrease body mass index, providing a
      feasible strategy to treat obesity.

      Nonetheless, findings from studies investigating the potential for a hypoxic environment to
      augment the exercise training response and subsequent metabolic health are equivocal.
      Notably, there is a paucity of information regarding the optimal combination of exercise
      variables and hypoxic load (i.e. level of hypoxia) to enable an individualized and safe
      practice of exercising in a hypoxic environment.

      In the present randomized, single-blind, cross-over study, the investigators will investigate
      the effects of single-bout of exercise under normoxia (FiO2, 20.9%), moderate (FiO2, 16.5%)
      and high normobaric hypoxic conditions (FiO2, 14.8%) (60-min cycling session at 90% LT) on 2h
      OGTT and 24h-glucose level in individuals with overweight. The investigators hypothesize that
      exercise in combination with hypoxia improves glucose homeostasis in individuals with
      overweight.
    

Detailed description: 
      In the present randomized, single-blind, cross-over study, participants will be exposed to
      normobaric 1) normoxia (oxygen level 20.9%), 2) moderate hypoxia (oxygen level 16.5%) and 3)
      high hypoxia (oxygen level 14.8%) 1) during exercise (60 minutes on a cycle ergometer) at 90%
      LT. Participants will be randomly assigned to each condition (computer-generated
      randomization plan), separated by a washout period (5-7 days). To accomplish this,
      participants will exercise in an environmental chamber in which oxygen concentration of the
      ambient air and, as such, oxygen levels can be closely controlled and monitored. Participants
      will cycle for 60 minutes at a 90% lactate threshold (LT), determined by an LT test.

      Visit 1 (Screening and consent):

      Introduction to the research team and tour of the facility. Complete and sign the Adult
      Pre-Exercise Screening System form. Complete and sign the consent information form.

      Visit 2:

      Body composition screening using bioimpedance analysis (Inbody 770, Cerritos, CA, USA) Blood
      pressure screening. Lactate threshold test-participants will be riding a Velotron cycle
      ergometer (Racermate, Seattle, USA) with an initial load of 50 Watts. The load increased
      progressively in 15 Watts increments every 4 minutes, with participants maintaining a
      constant pedal frequency (cadence ~90 rpm) until reaching LT.

      Visit 3:

      Baseline oral glucose tolerance test (OGTT)-Participants will be consumed 75 grams of glucose
      dissolved in water (Glucolin glucose powder) and blood samples will be collected to determine
      baseline glucose and insulin level.

      Visit 4:

      Attachment of Continuous Glucose Monitor (CGM) (FreeStyle Libre, Abbott Diabetes Care,
      Witney, UK) will be placed on the back of the upper arm as recommended by the manufacturer.

      Visit 5:

      Pre-exercise blood sampling-to determine plasma glucose, insulin and circulatory factors.

      Participants will be 60 minutes of cycling bouts at 90% of LT under simulated altitude
      exposure (normoxia or two hypoxic conditions) in the environmental chamber.

      Post-exercise blood sampling-2 hours OGTT will be performed immediately following each
      experimental trial to determine glucose homeostasis and circulatory factors.

      Visit 6:

      Post-exercise 24 hours blood sampling-to determine glucose homeostasis and circulatory
      factors.

      Removal of CGM
    

Intervention name(s): Low-moderate intensity exercise under normoxia; Low-moderate intensity exercise under moderate hypoxia; Low-moderate intensity exercise under high hypoxia
Intervention type(s): Other; Other; Other
Intervention description(s): The participant will perform the exercise interventions consisting of cycling at the 90% lactate threshold at normoxia (fraction oxygen: 20.9%) for 60 minutes on separate days (5-7 days). Immediately after exercise oral glucose tolerance test (OGTT) and 24-hour glucose concentration will be monitored continuously. Pre, post and post-24 h circulatory markers will be determined.; The participant will perform the exercise interventions consisting of cycling at the 90% lactate threshold at normoxia (fraction oxygen: 16.5%) for 60 minutes on separate days (5-7 days). Immediately after exercise oral glucose tolerance test (OGTT) and 24-hour glucose concentration will be monitored continuously. Pre, post and post-24 h circulatory markers will be determined.; The participant will perform the exercise interventions consisting of cycling at the 90% lactate threshold at normoxia (fraction oxygen: 14.8%) for 60 minutes on separate days (5-7 days). Immediately after exercise oral glucose tolerance test (OGTT) and 24-hour glucose concentration will be monitored continuously. Pre, post and post-24 h circulatory markers will be determined.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Participants will be required to complete 3 exercise interventions.
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Hypoxia; Overweight; Glucose tolerance; Exercise