Condition category
Nutritional, Metabolic, Endocrine
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
Publication status

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

Trial website

Contact information



Primary contact

Dr Beat Knechtle


Contact details

Facharzt FMH fur Allgemeinmedizin
Gesundheitszentrum St Gallen
Vadianstrasse 26
St Gallen

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

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


Study hypothesis

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 approval

Ethics Committee St. Gallen, Switzerland, 09/03/2011, Ref: 11/026

Study design

Randomized cross over trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


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.

Intervention type



Not Applicable

Drug names

Primary outcome measure

1. ANP
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
2. Lactate
3. Catecholamines (adrenaline, noradrenaline, dopamine)
4. Growth hormone (GH)
5. Insulin
6. Glycerol
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)]

Participant type


Age group




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
St Gallen

Sponsor information


Health Centre St Gallen (Gesundheitszentrum St Gallen) (Switzerland)

Sponsor details

c/o Beat Knechtle
Facharzt FMH fur Allgemeinmedizin
Vadianstrasse 26
St Gallen

Sponsor type

Hospital/treatment centre



Funder type

Hospital/treatment centre

Funder name

Health Centre St Gallen (Gesundheitszentrum St Gallen) (Switzerland)

Alternative name(s)

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)

Publication list

2013 protocol in:

Publication citations

  1. Protocol

    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.

Additional files

Editorial Notes

18/01/2019: Trial did not start due to a lack of funding.