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Cerebral Responses During Exercise in Hypoxia (CERVOX)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01614119
Recruitment Status : Completed
First Posted : June 7, 2012
Last Update Posted : June 7, 2012
Information provided by (Responsible Party):
University Hospital, Grenoble

Brief Summary:
While the exercise responses are classically described at the cardiorespiratory and muscle levels, recent data suggest that the brain is also significantly stressed by exercise and may even participate to performance limitation. In hypoxia in particular, cerebral responses to exercise may be altered and promote performance reduction during endurance exercise. In the present study, the investigators used innovative approaches to assess cerebral perturbations associated with exercise in hypoxia.

Condition or disease Intervention/treatment Phase
Brain Hypoxia Hypoxia Other: Hypoxic exposure Not Applicable

Detailed Description:

In the classical paradigm of exercise physiology, cardio-respiratory capacity and muscle fatigue are though to set the limit of exercise tolerance. However, there are experimental situations where it is not possible to explain exercise performance limitation using this classical paradigm, and it is therefore necessary to look for an alternative. Recent investigations highlight changes associated with exercise in the brain, e.g. changes in cerebral perfusion, cerebral oxygenation and neuron excitability. Also, several results suggest that in some conditions, the central nervous system fails to drive the motoneurons adequately, i.e. the so called central fatigue. However, the phenomenon of central limitation to exercise and its underlying neurophysiological mechanisms are still to clarify. Cerebral metabolism and neurohumoral responses during fatiguing exercise are therefore to investigate in order to propose a new paradigm able to explain exercise limitation. Among the conditions where the classical paradigm of exercise performance limitation does not appear to suit the actual observations, exercise under hypoxic environment appears to be particularly challenging. Some data suggest indeed that the cerebral response to exercise may be substantially modified in hypoxia compared to normoxia.

Hence, in the present project, the investigators aim to evaluate the effect of hypoxia on brain adaptation to exercise in healthy human. In particular, the objective is to assess the brain neurophysiological response to a fatiguing exercise, including cerebral perfusion and oxygenation, cerebral activation, cortical excitability as well as the resultant motor command while inhaling normoxic or hypoxic gas mixtures. To fulfil these objectives, complementary methodological approaches will be used during exercise both normoxic and hypoxic conditions: functional magnetic resonance imaging (fMRI) will be used to evaluate cerebral activation, the perfusion imaging arterial spin labelling (ASL) nuclear magnetic resonance method will assess regional cerebral perfusion, near infrared spectroscopy (NIRS) will allow measurement of cerebral oxygenation, measurement of motor evoked potential in response to transcranial magnetic stimulation (TMS) will assess the cortical excitability, measurement of the level of central activation (assessed by TMS) and the electromyographic (EMG) signals will evaluate the motor command. Moreover, to account for the effect of the muscle mass involved during exercise and the duration of hypoxic exposure, brain adaptation to exercise in hypoxia will be assessed for motor task involving small (thumb adduction) or large (knee extension, cycle ergometry) muscle groups as well as for acute (<1 hour) or prolonged hypoxic exposure (several hours: 6 hours). This multi-technical approach will be possible through this collaborative project between three partners experts in brain function investigation and exercise physiology (Institut Fédératif de Recherche 'RMN Biomédical et Neurosciences' Joseph Fourier University and University Hospital, Grenoble; 'Exercise Physiology' Laboratory, University Hospital, St Etienne; 'Motor Efficiency and Deficiency Laboratory', Montpellier I University, Montpellier).

The investigators hypothesise that hypoxia would enhance the cerebral perturbation associated with a given fatiguing exercise, i.e. would induce greater reduction in cerebral blood and cerebral oxygenation, greater reduction in cortical excitability and central activation as well as larger reduction in central command, and this particularly when a large muscle mass is involved as well as when hypoxic exposure is prolonged.

This project aims to renew our vision of the limitation of human exercise performance as well as our understanding of exercise tolerance under hypoxemic conditions. The later is relevant for sport and altitude medicine dealing with exercise and altitude tolerance, as well as for diseases characterised by hypoxemia and exercise intolerance such as respiratory diseases like chronic obstructive pulmonary diseases for example.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 30 participants
Allocation: N/A
Intervention Model: Single Group Assignment
Masking: Single (Participant)
Primary Purpose: Basic Science
Official Title: Evaluation of the Cerebral Responses to Exercise in Hypoxia
Study Start Date : June 2010
Actual Primary Completion Date : July 2011
Actual Study Completion Date : July 2011

Resource links provided by the National Library of Medicine

Arm Intervention/treatment
Experimental: Sportsmen
One single group of active healthy subjects was investigated
Other: Hypoxic exposure
Subjects breath either normoxic or hypoxic (FiO2 = 12%) gas mixture
Other Name: Hypoxia (FiO2 = 12%)

Primary Outcome Measures :
  1. Change in voluntary activation [ Time Frame: Baseline and after 4h of exercise ]
    Maximum voluntary activation level measured using TMS

Secondary Outcome Measures :
  1. Change in tissue oxygenation [ Time Frame: Baseline and after 4 hours of exercise ]
    Muscle and cerebral oxygenation measured with NIRS and fMRI

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Male
  • 18-50 yrs
  • No cardiovascular, respiratory or neuromuscular disorders

Exclusion Criteria:

  • Cardiovascular, respiratory or neuromuscular diseases
  • Contraindication for TMS and MRI

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01614119

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Grenoble University Hospital
Grenoble, France, 38042
Sponsors and Collaborators
University Hospital, Grenoble
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Principal Investigator: Bernard Wuyam, MD PhD University Hospital, Grenoble
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Responsible Party: University Hospital, Grenoble Identifier: NCT01614119    
Other Study ID Numbers: 1002
2010-A00121-38 ( Registry Identifier: ID RCB )
First Posted: June 7, 2012    Key Record Dates
Last Update Posted: June 7, 2012
Last Verified: June 2012
Keywords provided by University Hospital, Grenoble:
Additional relevant MeSH terms:
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Hypoxia, Brain
Signs and Symptoms, Respiratory
Brain Diseases
Central Nervous System Diseases
Nervous System Diseases