Front Matter

Chapter 7 Rehabilitation Physical Modalities 141

Precautions and contraindications

Caution should be used when applying cold
over superficial nerves, areas of decreased
sensation, or open wounds. Care should also
be taken when working with very small dogs
to avoid hypothermia. Cryotherapy should
not be used over areas of compromised circu­
lation or in patients with thermoregulatory
disorders or cold sensitivities. Patients should
be monitored for signs of nonfreezing cold
injuries (Khoshnevis et al., 2015, 2016) or other
injuries such as frostbite (Rivlin et al., 2014).
Furthermore, areas previously affected by
frostbite should not receive cryotherapy.
One final consideration: a cooled area can
require an extended period of time to return
to  baseline temperature (Akgun et al., 2004;
Khoshnevis et al., 2016). Cold can also increase
joint stiffness (Uchio et al., 2003) and tendon
stiffness (Alegre et al., 2016), and decrease pro­
prioceptive awareness (Alexander et al., 2016).
This can be important when providing cryo­
therapy prior to therapeutic exercises, or when
treating sporting or working dogs that will
return to activity soon after treatment.

Superficial heat

Superficial heat is used in the rehabilitation
setting to reduce pain, increase blood flow,
improve connective tissue extensibility and
joint mobility, and promote muscle relaxation.
During the subacute and chronic stages of
healing, heat application may also help allevi­
ate remaining inflammation. As with cryother­
apy, superficial heat is most frequently
delivered through conduction, with the heat­
ing agent placed directly onto the body part.
Superficial heating modalities are used to
increase tissue temperature up to 3 cm below
the skin’s surface (Draper et al., 1998) although
the greatest effects occur in the first 1 to 2 cm.
Depending on the treatment goal, the tempera­
ture of the target tissue must be increased by
1–4 °C to result in therapeutic effects (Draper &
Ricard, 1995). A tissue temperature rise of 1 °C
leads to an increase in metabolic rate, a 2–3 °C
temperature increase helps to alleviate muscle
spasm, pain, and chronic inflammation, and an

increase of 4 °C promotes collagen extensibility

(Lehmann et al. 1967a, 1967b; Draper, 2014).

Evidence supporting the use

of superficial heat

Therapeutic effects on pain

Superficial heat has been shown to effectively

reduce the perception of pain in human patients

including those with chronic knee pain (Kim

et  al., 2013; Petrofsky et al., 2016a), wrist pain

due to either soft tissue or joint involvement

(Michlovitz et al., 2004), and acute low back

pain (Nadler et al., 2003), with more rapid and

sustained relief as compared to oral ibuprofen

(Stark et al., 2014) or cryotherapy (Dehghan &

Farabod, 2014). Superficial heat therapy also

shows positive results toward improving the

discomfort associated with chronic musculo­

skeletal conditions in veterinary patients (Corti,

2014; Epstein et al., 2015).

There are several mechanisms through which

heat may reduce pain. With increased tissue

temperature, cutaneous blood flow is aug­

mented due to vasodilation (Baker & Bell, 1991;

Okada et al., 2005; Biyik Bayram & Caliskan,

2016). This may lead to pain relief if the source

of discomfort is related to tissue ischemia from

reduced blood flow (Ochiai et al., 2014) or

chemical mediators that stimulate nociceptors.

Increased tissue temperatures have also been

shown to increase pain thresholds, possibly

related to the release of endorphins and/or an

inhibition of afferent and efferent C fibers in the

area (On et al., 1997). Additionally, pain relief

may occur due to a decrease in muscle activity

in the area (Lewis et al., 2012) and/or the reso­

lution of muscle spasms, believed to be due to a

reduction of muscle spindle firing rates (Mense,

1978). Finally, superficial heat may act as a

counterirritant, reducing pain perception as

described in the gate control theory of pain.

Therapeutic effects on tissue healing

and protection

In the post‐acute and chronic stages of healing,

temperature elevation of injured superficial

tissues can support continued recovery by aug­

menting the delivery of nutrients and oxygen