To gain therapeutic benefit, the target tissue depth and
temperature should be considered when choosing the appropriate
thermal modality. When deep skeletal muscle (over a
small region) is targeted for heat treatment, both ultrasound
and microwaves are used clinically because both modalities are
thought to effectively heat the target tissue. Garrett et al
evaluated the changes in gastrocnemius muscle temperature
induced by short-wave diathermy, and found that 20 min of
microwave exposure induced an increase of 4.6°C in muscle
temperature. Another study reported that ultrasound produced
a mean temperature rise of 3.5°C in the gastrocnemius–soleus
complex.A few comparative studies have examined the use of
heat modalities on living tissue, such as muscle, and reported
that electromagnetic waves are more effective than ultrasound.
In general, the therapeutic range for sports medicine
is assumed to be from 41°C to 45°C. However, the increase in
temperature may depend on the thermal modality.