Plain English Summary
Background and study aims
Deep-water running (DWR) is a popular alternative form of training for athletes looking to increase training volume and for those who are unable to train sufficiently on land due to injury. The buoyancy of the water lightens the loading on the legs but does not decrease the performance level of the heart nor the circulatory system. DWR could therefore be a valid form of aerobic training as it enables the athletes to keep their training volume high without increasing the risk of injury.It has been proven that it is possible with DWR training to maintain or even improve aerobic capacity (the ability of the heart and lungs to get oxygen to the muscles). DWR can therefore be considered as a good alternative when the goal is to increase an athlete’s fitness level. Studies have investigated the effects of DWR with endurance athletes, but DWR is also used by athletes from teams sports such as football. Therefore, there is a need to investigate the effects of DWR in such sports, where agility and explosive abilities are essential for high level performance. However, there is concern that DWR may impair these properties due to the lack of ground contact, changes in muscle activation and speed of movement. To date, this has not yet been rigorously tested. Therefore, there is a need for research investigating how football players’ neuromuscular (nerve and muscle) system responds to a DWR program and not just aerobic fitness. The aim of this study is to find out whether DWR is an effective training method to improve aerobic power in female football players.
Who can participate?
Healthy female football players aged 15-25, recruited from a single football team in Iceland
What does the study involve?
The participants undergo tests of their oxygen consumption on a land-based treadmill, an agility test, a speed test, a kick speed test, and perform counter movement jumps (CMJs). Participants are requested to rest for 24 hours before each test. After the tests, the participants are randomly allocated into two groups. Both groups perform three 45 minute training sessions a week, one group in water and the other on land. Also, all participants take part in their football team practices (3 times a week + 1 game). The training of both groups is conducted by trained individuals. The training intervention lasts for 8 weeks. The tests are repeated within 4 days after completing the training program.
What are the possible benefits and risks of participating?
All participants are provided with individually prescribed training either on land or pool. Each session is completed in small groups with each session being supervised by trained coaches. Additional to the training benefits, each participant receives personal feedback on aerobic fitness and neuromuscular function. After the intervention period the coaches of the football team are provided with feedback from the aerobic and neuromuscular outcomes, with suggestions for future development. Additionally, each coach receives training and example programs from both the land and water based training. This study consists of two high intensity exercise programs, prescribed to active, training female athletes. However, there are still some risks associated with participation in this study. As with any exercise testing there is a risk of abnormal blood pressure, fainting, irregular, fast or slow heart rhythm, and in rare instances, heart attack, stroke or death. There is a risk of muscle or joint injury during the neuromuscular function testing, but this will be minimised with appropriate warm up and cool down as well as full instruction of correct techniques for each test. Only athletes with suitable footwear for the facilities will be allowed to complete the test. Complications related to the intervention include increased muscle soreness after training, predicted to be higher after land training than pool training, as well as a risk of injury.
Where is the study run from?
Reykjavik University (Iceland)
When is the study starting and how long is it expected to run for?
December 2017 to April 2018
Who is funding the study?
This project is funded primarily by Reykjavik University with assistance from the Football Association of Iceland and Breiðablik Club (Iceland)
Who is the main contact?
Dr Jose Saavedra
The effect of deep water running on aerobic fitness in female football players: a randomized controlled trial
The SAFE trial (Soccer Aquatic FitnEss trial)
A program of deep water running is an effective training method to improve aerobic power in female football players.
The ethics board of the Háskólinn í Reykjavík, Reykjavik University, 16/10/2017, ref: 2017-002
Randomized controlled trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Not available in web format, please use the contact details to request a patient information sheet
The subjects are randomly divided into two groups. Randomisation will be completed using an external researcher with no interest in the study. The allocation will be concealed by providing the researcher with only ID number with no identifying information. Randomisation will be completed using STATA (Version 14.0). Both groups will perform three 45 minute training sessions a week, one group in water (G1) and the other on land (G2). Also, all the subjects will take part in their football team practices (3 times a week + 1 game). During the workout sessions, the subjects will train on their individual fitness level devised from a condition specific, i.e. land and water, maximum aerobic capacity test. The workouts consist of medium to hard intensity intervals and easier, aerobic bouts. The intensities between the two training groups will be matched with heart rate. The training of both groups will be conducted by trained individuals. The training intervention will be 8 weeks.
Primary outcome measure
Maximal oxygen consumption (VO2max) testing will be performed on a land-based treadmill. The runners will perform an incremental treadmill test starting at 8 km/h followed by an increase of 1 km/h every second minute until exhaustion. The slope will be kept at 0.5 degrees during the whole test. Heart rate will be recorded continuously using a heart rate monitor. Oxygen consumption will be measured breath-by-breath throughout the test using a portable gas analyzer. To analyze blood lactate concentration, the treadmill will be stopped after each 2-min stage for about 10-20 s to take a fingertip sample. At baseline (at rest), after each increment and immediate after the following the maximal oxygen measurements Rating of Perceived Exertion (RPE) will be asked to assess athlete’s perception of fatigue, as RPE can be considered a good indicator of global internal load when used with trained athletes (Impellizzeri et al. 2004). The highest 60-s VO2 value during the treadmill test will be selected as maximal oxygen uptake (VO2max). Measured prior to randomisation (within one week of initiating the training program) and within 4 days after completing the 8-week training program
Secondary outcome measures
Measured prior to randomisation (within one week of initiating the training program) and within 4 days after completing the 8-week training program:
1. Lower body power will be measured with a countermovement jump (CMJ) test. Flight time and height will be measured with a high speed camera. Subjects will perform the CMJ five times with a 15-20 seconds rest between the jumps. They’ll place their hands on their hip and feet shoulder width apart.
2. Agility will be tested on a flat, non-slip surface with the Illinois agility test. Four cones will be placed on the ground as markers, the length of the course is 10 meters and the width is 5 meters. Another four cones will be placed in line in the middle, 3.3 meters apart. The subject lies down on her stomach with her arms at her side. At starting command, she gets up and runs through the course as fast as possible. The time to complete the course will be the result.
3. Speed will be tested with 5*30 m max sprint test. The subjects run 5*30 m maximal sprints with a 25 seconds rest between each sprint. The time of each sprint is measured with light sensors.Before the sprints the subjects do a proper warm-up, led by the researchers, including 2-3 times 20 m full acceleration sprints at 90-95% max speed.
4. Maximum kicking speed is measured with a speedometer. The subject performs a penalty kick to the center of a goal and the speed of the ball is measured. Each subject gets two tries with the left and two tries with the right leg.
5. Muscle soreness experienced will be monitored using a VAS (0-100mm)
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Female aged 15-25
2. Post puberty
3. Second team level (at least two years of training) football players
4. Ability to read, understand and sign informed consent
5. Ability to attend all sessions including the familiarization session for DWR, and the two or three testing sessions.
6. Healthy with no medical, e.g., cardiovascular disease, musculoskeletal disease or injury reason prevention participation in a maximal oxygen consumption test
Target number of participants
Participant exclusion criteria
1. Female older than 25 years old
2. Female pre puberty
3. Non-ability to attend all sessions including the familiarization session for DWR, and the two or three testing sessions
4. Disease or infection preventing full participation in measurements
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Physical Activity, Physical Education, Health and Sport Research Centre (PAPESH) Menntavegur 1, Nauthólsvík
Sports and Health (PAPESH) Research Centre
Results and Publications
Publication and dissemination plan
The results of this study will be published in the form of at least two high-impact peer reviewed journals in the fields of sports and health sciences.
IPD sharing statement
The datasets generated during and/or analysed during the current study are not expected to be made available due to the inclusion of participants below the age of 18 years old.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)