Introduction

Our body temperature is maintained within a range of 36°C–37.5°C, independent of the surrounding environment, whether it is cold or hot. Various mechanisms in our body regulate the temperature within this range. Thus, any deviation from this range may indicate that you are ill or suffer from hypo or hyperthermia.

Thermotherapy (heat therapy), which involves the targeted application of heat or cold (cryotherapy) to improve the symptoms of certain conditions, offers many therapeutic benefits.¹ It is a low-cost treatment option that is widely available for use at home or in professional settings. As we age, many of us experience acute or chronic pain in the neck, shoulders, or lower back. Increasing evidence suggests that non-pharmacological thermotherapy effectively provides pain relief and offers numerous other health benefits.

Mechanism of thermotherapy

Heat transfer in tissues

We can be exposed to temperatures above or below our body temperature. However, our body has highly effective thermoregulatory mechanisms that maintain our internal temperature close to 37°C, allowing us to function in extreme conditions. To achieve this, we need to generate our own heat through metabolism, where large molecules derived from food are broken down into smaller ones and provide energy.

All temperature differences require the transport of heat from where it is produced to where it is needed. The circulatory system including the heart, blood vessels, and blood is responsible for transporting heat around the body. The mechanisms of thermotherapy use existing pathways of heat distribution, such as the heat contained in blood as it flows through the complex network of arteries, veins, and capillaries. For decades science has developed complex mathematical models to quantify heat distribution throughout the human body.² The key factors include:

• Blood perfusion, which is the flow through capillaries and extracellular spaces measured as flow rate per volume of tissue
• The size and number of existing blood vessels
• Variations in thermal properties

Poor blood perfusion can lead to cold hands and feet, joint pain, and muscle cramping. Therefore, improving heat transfer to an optimum level may have therapeutic benefits. 

Physiological responses to heat

The regulation of temperatures uses nerve receptors that detect temperature increases and trigger physiological responses, such as dilation of blood vessels, which increases heat transport to the skin. At a certain point, the body starts sweating to cool the skin further. Increased blood perfusion to the skin carries more blood to tissues, which assists in the transport of nutrients and oxygen, as well as the removal of waste products. Thus, applying heat may improve skin conditions and support the recovery of damaged tissues.

Impact on muscle relaxation and pain relief

Applying heat to muscle tissue increases blood flow, resulting in muscle relaxation and increases nutrients and oxygen levels. Thus, heat treatment is beneficial if you have sore muscles and joints, and is recommended for arthritis. 

Severely swollen and painful joints can be improved by applying cold, which reduces blood flow, thereby mitigating swelling and improving symptoms. In some cases, it may be debated which treatment—hot or cold is more appropriate.

Types of thermotherapy

Moist heat

Moist heat treatment includes moist hot packs placed on the affected area, e.g. necks, shoulders, or back. It helps to relax the muscles and soft tissues, making them less stiff and more flexible. Physical therapists frequently use moist heat to promote flexibility and improve overall joint flexibility and range of motion. The moist heat penetrates deeper into the muscle tissues and increases blood flow.

Dry heat

Dry hot packs are preferred for minor conditions due to their consistent temperature and ease of application. They are commonly used for minor back tension for a short duration, usually 15-20 min. However, for severe or chronic conditions, the application time can be extended to 30 min. It is crucial to carefully consider the temperature of the pack to avoid burns, and sleeping with heat packs is not recommended.

Infrared heat therapy

Infrared light is emitted at an invisible frequency that we experience as heat. Only a few scientific studies have covered infrared heat therapy for back or shoulder issues. However, it was observed that patients with lower back pain who received infrared treatment had significantly reduced pain on a numerical rating scale which showed reduced pain from 6.9 to 3 (3.9 reduction), whereas in the untreated patients group the value fell from 7.4 to 6 (only 1.4 reduction).³

Further studies of infrared red therapy have also shown benefits in a wide range of conditions, including cardiovascular conditions, congestive heart failure, dementia, and beauty treatments.

Efficacy and benefits of thermotherapy

Clinical studies supporting thermotherapy

The benefits of three treatment options, heat, cold, and pharmacological intervention for patients with acute lower back pain, were compared in a scientific study.⁴ The study concluded that both heat and cold treatment showed significant improvements in the patient’s well-being. The best results were achieved when all three treatments were applied together.

Moreover, a recent review of the scientific literature suggested that superficial and continuous heat therapy of patients with acute or chronic lower back problems provides pain relief, improves muscular strength, and increases flexibility. Thus, thermotherapy is recommended as a low-cost, non-pharmacological alternative in clinical practice.⁵

Comparison with other pain management methods

A 2020 study was conducted to compare the effects of neck stabilisation exercise versus thermotherapy and neck stabilisation exercise on chronic neck pain. 35 patients with chronic neck pain were allocated to two groups. Group 1, received thermotherapy with a salt pack in conjunction with neck stabilisation exercises. Whereas, Group 2 performed only a neck stabilisation exercise. Group 1 showed significant improvement in muscle properties and stiffness, neck pain, and alignment of the neck and shoulder. Accordingly, these results recommend the use of thermotherapy combined with neck stabilisation exercise as a complementary intervention for chronic neck pain control.¹ 

Safety considerations and contraindications

Heat therapy has potential risks if applied incorrectly. These risks include skin rash or burns, often caused by the heat source being too hot or applied for too long.

Patients with cardiovascular issues, such as hypotension, may find heat treatment problematic due to its potential to further reduce blood pressure. In addition, thermotherapy may also increase heart rate, posing risks for people with arrhythmia.

Moreover, heat treatment is contraindicated after injury, on open wounds, or during infection, as it may exacerbate swelling and inflammation.

Further contraindications include:

• Dermatitis: Heat therapy can exacerbate flare-ups
• Deep vein thrombosis: Heat treatment can dislodge a blood clot, potentially causing severe damage if it settles in the brain or lungs
• Patients with chronic heart failure: Avoid jumping into an ice or cold bath after sauna, as the body may have an impaired ability to increase blood flow 
• Diabetes patients: Heat treatment may reduce blood sugar levels 
• Severe cognitive impairment such as dementia: Patients may have difficulty remembering correct heat application times; support may be necessary for safe use of heat treatments in such cases

FAQs

Does thermotherapy work?

There is overwhelming empirical evidence, supported by an increasing number of scientific studies, that both hot and cold treatments can provide instant pain relief and muscle relaxation.⁶

Is thermotherapy expensive?

One of the advantages of thermotherapy is that it is relatively low-cost, as heat can be applied in simple heat packs and cold can be provided with packaged ice cubes. It also does not require the purchase of medicines, thus avoiding potential side effects.

Is thermotherapy dangerous?

Generally, thermotherapy is a low-risk therapy. However, treatment time needs to be observed, and extremes in both high and low temperatures should be avoided. 

Summary

A sedentary (desk and screen-based) lifestyle is responsible for increasing the number of people suffering from neck, shoulder, and back pain, which tends to worsen with age. Thermotherapy is a suitable, low-cost, non-pharmacological intervention for neck and shoulder, stiffness and pain, using either heat or cold. There is a wealth of evidence demonstrating significant benefits from both forms of therapy for many patients, and they are expected to play an increasing role in the future.