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What is ultrasound?

What is ultrasound

There are different types of ultrasound. In sports therapy, we use therapeutic ultrasound, which creates sound waves to produce an effect within the tissue it is applied to. Therapeutic ultrasound is different to diagnostic imaging ultrasound which is used to diagnose injuries such as tears or bursitis, or used during pregnancy.

How does therapeutic ultrasound work?

In the head of the ultrasound, the transducer, there is a piezoelectric crystal, which an alternating current flows through. When the current is flowing, the vibration of the crystal creates high frequency sound waves that are inaudible to the human ear. The sound waves are of such high frequency they must be transferred through a type of medium to penetrate into the body; this is why ultrasound gel is used or it is delivered through water. Based on a range of application settings, the ultrasound will have different effects.


What are the different settings used for?

Here are some of the settings that can be adjusted:


This determines the depth of penetration of the waves.

  • 1MHz is a deeper application reaching 5cm into the tissue; this would be used on a large muscle.

  • 3MHz is for superficial areas reaching a depth of 2 cm; this depth would be appropriate for a tendon in the hand.

Continuous or pulsed

  • The continuous setting refers to the sound waves continually being transferred into the treatment area. This is applied to chronic injuries.

  • The pulsed setting results in a fluctuation of the output. This is applied to acute injuries.


The intensity used is determined by the current state of the tissue, whether it is acute (new injury), sub-acute or chronic (old injury).

Treatment time

Treatment time is dependent on the size of the area being treated, the frequency and intensity being used (5-15 minutes).

A therapist will determine the settings based on an assessment of the injury noting the stage of healing, inflammatory state, size of the area and the goals for the treatment.


How does ultrasound help?

Depending on the type of setting the sports therapist uses, the following effects can take place:

  • Decreases pain

  • Aids in tissue healing, for example calf muscle strain

  • Helps increase joint motion and tissue flexibility

  • Aids in reducing swelling


When should you avoid using ultrasound?

As with all treatment options, there are contra-indications to using ultrasound.

The following are times when an ultrasound application should not be used:

  • metal, surgical or cosmetic implants (ex, screws, rods, pacemakers, etc)

  • major artery, nerve or regenerating nerve

  • deep vein thrombosis

  • cancer or undiagnosed lumps/ bumps

  • circulatory or sensation impairments

  • skin conditions

  • pregnancy – don’t use around torso or reproductive organ – extremities are okay with no other contra-indications present

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