Hydrotherapy (aquatic physiotherapy)

Hydrotherapy or aquatic physiotherapy is exercising in water.

The main problems of AS are stiffness, pain, risk of developing a stooped posture and tiredness or fatigue. Exercising in water addresses all of these problems:

  • The warmth and the buoyancy make stretches more effective
  • You don't feel so much pain
  • It's easier to stay upright because the effect of gravity is less
  • Exercising in water requires less effort
  • Afterwards you usually have a really good night's sleep!

Most importantly, water gives you freedom of movement.

Some people are a bit reluctant to be seen in swim wear. Remember that water is a great equaliser and in water we are all similar, so don't worry.

Do check out the safety tips at the bottom of the page before trying out aquatic physiotherapy.

Water is supportive, helping you move more easily

With any physical impairment, moving becomes a problem. When you move less, your muscles become weak, your joints stiffen up, you become less fit and your balance reactions become less reliable.

On land you have to work against the force of gravity. In water there is another force, which doesn't pull you down like gravity does, but pushes you up. This force is called up thrust and it actually helps us move. Your body feels lighter; in waist deep water you weigh around half of what you weigh on land.


Water acts as a shock absorber

Aerobic exercise is not recommended for people with AS on dry land, because of the impact on the feet, knees, hips and spine. The water provides shock absorption and makes this type of exercise a lot safer and more enjoyable.

Water acts as resistance to help build muscles


Warm water helps you relax

The water temperature in hospital aquatic physiotherapy pools is usually around 33-34 degrees Celsius. The warmth of the water helps you to relax and tight muscles can be stretched more efficiently when they are relaxed. 

Top safety tips

Consult your doctor or physiotherapist before you try exercising in water.

The area around the pool is likely to be wet and slippery. Take care when walking on a wet floor, don't run or rush. You can wear flip flops or beach shoes and if you normally use a stick or crutch, it's much safer to use a walking frame instead, as a stick can very easily slip when wet.


Only do the exercises shown by your physiotherapist. Do not perform your dry land exercise programme in water: not only is it not effective, but it could even do more harm than good.

Don't use hydrotherapy if you have:

  • Unstable blood pressure
  • Uncontrolled diabetes
  • Angina at rest or shortness of breath at rest

If you have compromised lung function you may find the pressure of the water on the chest and ribcage too much when in the deep end.

If you suffer with asthma or angina, always take your inhalers and sprays with you and leave them on the pool side, so they are there should you need them. 

Where to find hydrotherapy


Ideally you should work in a heated pool designed for aquatic physiotherapy. You can of course use your local swimming pool once you know the exercises, but the temperature of the water will be lower. Keep moving so you don't get too cold. Swim a few lengths, do a few stretches, swim a bit more etc. 

Enjoy your sessions!

Ankie Postma, secretary of the Aquatic Therapy Association of Chartered Physiotherapists (ATACP)

Last reviewed: April 2015