Plain English Summary
Background and study aims
We are carrying out a study on 10 to 14 overweight persons to find the best form of endurance exercise (exercise to build up stamina) in water for weight loss. Continuous endurance exercise improves fat metabolism. Fat metabolism can be further improved using high intensity intermittent exercise. When exercising in water a physiological agent that is produced in the heart called atrial natriuretic peptide (ANP) is released. This agent leads to an improved mobilization of body fat. The combined effects of endurance exercise and water immersion may help to reduce bodyweight in an optimal way.
Who can participate?
Healthy overweight men aged between 18 and 50 years
What does the study involve?
The participants` physical fitness will be tested before the actual testing procedure. Body fat will be measured. Then the participants will be allocated to either the High Intensity Group or the Continuous Exercise Group by a process called randomisation which is like a coin toss. Then the participants will change groups and exercise modalities. At the end of the study we will compare the effectiveness of the two different exercise modalities in regard to optimum weight loss.
What are the possible benefits and risks of participating?
Participants will gain insight into physiological research. Moreover, the results of the ECG, the lung function test and the exercise test will be discussed. Adequate health focused training recommendations will be provided.
Study will be only conducted with healthy men without detected risk factors. The risk of an undetected coronary heart disease and sudden death will be reduced to a large extent by the preliminary medical check-up. The risk increases with age; therefore the age limit is 50 years. A defibrillator will be available. Moreover, the standard emergency equipment required will be on hand.
Where is the study run from?
Medical Health Centre, Bad Ragaz, Switzerland
When is the study starting and how long is it expected to run for?
The study will start on in July 2013 and will run for three months
Who is funding the study?
Health Centre St Gallen (Gesundheitszentrum St Gallen), Switzerland
Who is the main contact?
Dr Beat Knechtle
Does continuous endurance exercise in water elicit a higher release of atrial natriuretic peptide (ANP) and a higher plasma concentration of free fatty acids (FFAs) in pre-obese and obese men than high intensity intermittent endurance exercise? A pilot study
The aims of the study are to investigate:
1. Whether continuous endurance exercise or high intensity intermittent endurance exercise in water elicits both a higher release of ANP and a higher plasma concentration of FFAs
2. To determine whether continuous endurance exercise in water or a high intensity intermittent endurance exercise in water would lead to a more pronounced short term (two hours) excess post-exercise oxygen consumption (EPOC) effect.
Ethics Committee St. Gallen, Switzerland, 09/03/2011, Ref: 11/026
Randomized cross over trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet
Ten to fourteen healthy sedentary pre-obese and obese class-1 men with a body mass index (BMI) ranging from 25 34.99kg/m2 according to WHO 2004 will be scrutinized with regard to their metabolic responses to a continuous exercise in water and to a high intensity endurance exercise in water. Both trials will be matched for energy expenditure. After preliminary testing, the tests will be conducted as repeated measurements. The two different exercise protocols [Continuous endurance exercise and High intensity intermittent endurance exercise] will be compared.
Blood samples will be taken by laboratory assistants who are familiar with the operating procedures and safety standards.
During the trial blood samples will be taken every 15 minutes (continuous endurance exercise) or after each exercise step (high intensity intermittent endurance exercise). Moreover, one blood sample will be taken pre- and post-exercise.
Primary outcome measure
2. Respiratory exchange rate (RER). The RER specifies the ratio of carbon dioxide (CO2) eliminated to oxygen (O2) consumed. The RER depends on the metabolic substrate used for generating energy. Using stoichiometric equations, the RER can be applied to determine the amounts of carbohydrates and fatty acids metabolized. Energy production can also be reliably estimated in the same manner.
3. The rating of perceived exertion (RPE). The RPE method requires that a person subjectively rates how difficult the work is, using a numerical scale that is related to exercise intensity.
Secondary outcome measures
1. Free fatty acids
3. Catecholamines (adrenaline, noradrenaline, dopamine)
4. Growth hormone (GH)
All of which indicate changes in the metabolic process.
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Lack of funding/sponsorship
Participant inclusion criteria
1. Male gender (Differences in estrogen concentrations between men and woman result in greater reliance on fat oxidation during exercise in woman. Between the different phases of the female menstrual cycle substrate utilization also varies)
2. Body-Mass-Index >25 and <34.99 kg/m2
3. Age > 18 and <50 years
4. Verbal and written information of the participants, signed declaration of consent
5. No cardiovascular risk [completion of the Physical Activity Readiness Questionnaire (PAR-Q)]
Target number of participants
10 to 14
Participant exclusion criteria
1. Female gender
2. Cardiac insufficiency > New York Heart Association (NYHA) 1
3. Continuous arrhythmia
4. Respiratory obstruction
5. High blood pressure (> 140/90mmHg)
6. Body-Mass-Index <25 and >34,99 kg/m2
7. Age <18 and >50 years
8. Any medication
9. Signed declaration of consent missing
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Facharzt FMH fur Allgemeinmedizin
Health Centre St Gallen (Gesundheitszentrum St Gallen) (Switzerland)
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Basic results (scientific)
2013 protocol in: http://www.ncbi.nlm.nih.gov/pubmed/24112444
Karner-Rezek K, Knechtle B, Fenzl M, Gredig J, Rosemann T, Does continuous endurance exercise in water elicit a higher release of ANP and BNP and a higher plasma concentration of FFAs in pre-obese and obese men than high intensity intermittent endurance exercise? - study protocol for a randomized controlled trial., Trials, 2013, 14, 328, doi: 10.1186/1745-6215-14-328.