Which modality increases tissue temperature to enhance collagen extensibility and joint mobility?

• A. Cryotherapy
• B. Thermotherapy
• C. Ultrasound
• D. Electrical stimulation

Answer: (B)

Thermotherapy increases tissue temperature, which makes collagen fibers more pliable and able to deform during movement. As temperature rises toward the 40–45°C range, collagen extensibility improves, reducing tissue stiffness and allowing greater joint mobility when ROM is assessed or when stretching is applied. Heating also enhances local blood flow and can decrease muscle guarding, both of which support easier movement. This is why heat-based interventions such as warm blankets, moist heat, paraffin, or hydrotherapy are used to improve extensibility and ROM. Cryotherapy does the opposite by cooling tissue. Ultrasound can produce heating if used continuously, but the goal described here is the heating effect itself, which is most directly achieved with thermotherapy. Electrical stimulation, depending on parameters, typically modulates nerves or muscle activity rather than primarily increasing tissue temperature to enhance collagen extensibility.