Water Interval Training. Have you tried it?

Updated: Mar 10

Article by the Hydro-actif team

The short, high-intensity interval training versus longer, slower duration training has been studied and debated for decades among athletes, coaches, and scientists. Currently, the popularity pendulum has swung towards high-intensity interval training. Some recent investigations on untrained or moderately trained subjects have suggested that 2-8 wk of 2-3 times weekly intense interval training can induce rapid and substantial metabolic and cardiovascular performance improvements (Daussin et al., 2007; Helgerud et al., 2007; Talanian et al., 2007).

Many fitness experts, now argue that, high-intensity interval work is the only form of training necessary for weight loss and metabolic but proceed with caution. HIIT, as it is commonly referred to gives you quick gains but also a quick reversal if not combined with a long term programme. The effects are also better achieved if you have a strong endurance base. It isn’t for the faint hearted or beginner to exercise.

The available evidence suggests that combining large volumes of low-intensity training with careful use of high-intensity interval training throughout your training is the best-practice model for metabolic development. Translating this to water exercise can be fun, motivating and effective.

Water offers a challenging training environment through the properties of water such as hydro-static pressure, buoyancy, resistance and drag. These can be used to work at a high intensity in the pool, creating that interval based approach and aiding weight loss

No longer is water aerobics considered just for the elderly. You can be creative with the properties of water and apply modern approaches to training such as tabata training, short interval training or long interval training. University of New Mexico exercise physiologist Len Kravitz, states that in water you can facilitate high energy expenditure workouts with minimal risk of injury because water is 800 times more dense than air. Kravitz reviewed the research studies associated with various forms of water exercise and reported that aerobic activities that used the arms and legs in chest-deep water required a significant increase in energy expenditure to that of the same exercises performed on land. Imagine applying that to high intensity interval training session. Water ‘Insanity’ here we come.

Understand the properties of water and you can use them to your advantage to gain that high intensity needed. Read on!


Water has approximately 12 times the resistance of air. This aids muscular strength and endurance and can increase intensity for the exerciser; however it also slows their movement down. Resistance occurs from the viscosity of the water, water is more viscous than air. When the viscosity is high the flow of fluid is slower and resistance is higher. Viscosity of water generally decreases as temperature increases.

In water there are 4 types of resistance; Surface tension, Frontal resistance, Eddy drag and Viscous drag

Surface tension

The surface tension of water offers a greater resistance as it is more viscous. Moves that break the surface tension may be more difficult. So raising the arms above through the surface with big plyometric jumps and then breaking back down can raise the intensity of that move.

Frontal Resistance

There is more frontal resistance in water than sideways as there is more mass meeting it head on. There is more resistance when the hand hits the water flat on than sideways on. It is 3x harder to move in waterIncreased intensity of all movesLarger surface area and increased speed lead to greater intensity, running forward with flat hands behind will increase the intensity

Drag Forces

Drag forces are always present when moving through water

Eddy drag

As the limb moves small eddy’s of currents are created alongside of it. These whirlpools increase along with resistance if the limb is slightly bent.Decreases the ability to change direction quicklySculling uses this resistance

Viscous Drag

Viscosity = ability to pourWarm water is less viscous than cold water therefore easier to travel throughSkin friction = caused by resistance of water immediately next to the body. Water sticks to body and adds to resistance.Tail suction = water not being able to fill in behind the poorly streamlined body so the body pulls along a certain amount of water from behind. Formed behind the body. Participants can cheat by travelling behind someone!

Streamlined or Turbulent water movement

Water resistance due to turbulent flow is greater than that due to streamlined flow. Pressure builds in front of an object and decreases behind it as it moves through water; this creates a wake behind which water flows into. Eddy’s can form in the wake and this tends to draw the object back. The faster the movement the greater the drag back.

When a group is working together, more drag and turbulence can be created so those on the outside may have to work harder.


When a body is immersed completely or partially in water it experiences an upward thrust equal to the weight of the water it displaces. It appears that your body is lighter in water than on land.

A body in water has two opposing forces, buoyancy and gravity. The force of gravity relates to a body’s density - the more compact or dense a body is the less buoyant it is.

The centre of buoyancy is the chest area and the centre of gravity is the hip area. If the body is suspended in water i.e. deep water running, it rotates around the centre of buoyancy rather than the centre of gravity. Centre of buoyancy and gravity must be kept in a vertical line for equilibrium and alignment.

Buoyancy is determined by:

Body Type (Lean body mass sinks, Body Fat floats)

Body Fat distribution (Upper body = vertical floater, Lower body = horizontal floater

Air in Lungs (more air in lungs = more floatation)

Buoyancy also affects movement in water:

Buoyancy Assisted = a move in the same direction of buoyancy i.e. arm lift or jump up.

Buoyancy Supported = water supports the body or extremity i.e. a person standing in water and experiencing buoyancy support.

Buoyancy Resisted = a move in the opposite direction to buoyancy force i.e. returning limbs from flexion.

So when a limb moves towards the surface = buoyancy assisted

Stays at the surface = buoyancy supported

And returning = buoyancy resisted.

Buoyancy gives water a cushioning effect. There is a 90% apparent weight loss in shoulder depth water; participants are able to exercise with less biomechanical stress during each foot strike. This is important if participants are suffering from injuries, arthritis etc. as it reduces the stress on their joints.

Force absorption

The water slows down a movement returning to the pool bottom cushioning the impact stress.


This is the tendency of mass (an object) to resist changes in motion. I.e. a mass at rest tends to remain at rest; a moving mass tends to remain moving at a constant speed unless acted upon by a force. In order to overcome inertia a force must be applied.

The force to overcome inertia may be used to increase intensity of a work out by repeatedly applying force to overcome inertia. I.e. changing direction, moving off the spot, or changing muscle group used.

Changing steps frequently will increase the intensity of a workout.

Changing steps requires more time and more energy to overcome inertia and start a new movement.

Stationary inertia = beginning from a static positionMoving inertia = already moving but needs to continue to apply force to keep moving.Inertia lag = drag or friction - loss of forward momentum and requires extra force to overcome it and continue to move.


The acceleration of a mass depends on the size of the mass and the force applied. The principle of acceleration applies at the start of the movement. A strong person jumping forward in the water will cover more ground more quickly than a week one and exert more energy. However a smaller person may be able to accelerate more quickly because of less mass but they would use less energy and cover less ground. A large person would have to use more energy to accelerate at the same speed.

A strong person therefore or a person putting in more effort will achieve a higher intensity of workout.


Newton’s third law of motion states: “For every action there is an equal and opposite reaction.

Propulsion harnesses this property and can be used to:

Create directional movementRemain stationaryAid balance (sculling)Maintain floatation (treading water)

Muscles may be required to fixate heavily to prevent an “opposite action”.

Intensity can be increased by using resisted arm movement or decrease it by using assisting arm movement. E.g. jogging backwards with arm movements sweeping forward = assisted arm movement.

Consider alignment in resisted arm movement - if the water resists the arms as well as the body, the head, shoulders and feet may move forward faster than the body and impede safety and alignment.

Strong individuals who can maintain alignment may play with this principle and inertia to increase intensity.


Shorter levers require less force than longer levers to move through the same distance through the same resistance. E.g. fwd kicks - fwd knee lifts, jacks with bent arms - jacks with straight arms.


Specific gravity of water is 1, so

Relative density > 1 will sink

Relative density < 1 will float

Specific gravity of the human body is generally between 0.96 and 0.974 therefore people float. When all air is expelled this increases to 1.050 - 1.084 therefore humans sink when the lungs are empty.

People with a higher muscle mass have a higher relative density and are more likely to sink as muscle has a higher relative density than fat.


This is the pressure exerted by any fluid on the body at rest. The body never rests in water therefore the synergistic muscles and fixator muscles are constantly working to stabilise the body. This means it is important to cue core muscles.

Hydrostatic pressure is equal on all body surfaces however it increases with depth of water. Pressure of water around the rib cage makes it harder to fill the lungs, (shallow breathing may occur) – encourage clients to take deep breathes and consider the effects on asthma sufferers in deep water.

This pressure also assists venous blood return to the heart which can cause lower heart ratesin water exercise than land based. It also improves circulation and decreases the effect of blood pooling. This can be really advantages in the low intensity recovery blocks as well as lessening the overall perceived exertion in the high intensity blocks allowing people to work harder.

Getting Back To Fat Loss Interval Training Using The Properties Of Water

The one element of a fat loss workout that can be applied is a max calorie out workout. Working as hard as you can in as short as space a time as possible is an effective workout in the water. This will enable your clients to cause a calorie deficit and therefore weight loss over time.

Here is a little bit of fun. Workout how much weight you may lose working out in the water.


A typical fat loss water based exercise programme maximizes the use of interval training. Typically this can be one minute of intense aqua aerobic exercise with two to three minutes of recovery, tabata training, 20 secs of high intensity with 10 seconds rest 8 times or long interval blocks of three minutes of high intensity work and one minute minute of active rest.

Work Interval Blocks

After a suitable warm up, structure your intervals using the long interval approach. An interval cycle consists of a combination of one high intensity three minute block and one lower intensity one minute block. Most water interval programs have six to nine cycles. Work segments include plyometric-type jumping jacks, which involve landing with the knees deeply bent. Gun drills. Back lunge to high knee with power jump as knee lifts. Simulated tire runs require you to run through the pool, bringing your legs out and in as if you were running through tires. White water runs using fast resisted arms movements with your arms behind your body. Run as fast as possible to create a turbulence, fitter people on the outside of the circle, which adds resistance to the workout. Cross-country ski movements and side-to-side mogul jumps, landing with the feet together, are other examples.

Why not join us at the Hydro-actif on one of our Shallow Water course when myself and other presenters will be presenting more on this valuable area of work.

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