Which modality is a superficial heat option commonly used in clinics?

• A. Cryotherapy bag
• B. Electrical stimulation
• C. Hydrocollator packs
• D. Ultrasound

Answer: (C)

Superficial heat modalities warm the skin and the tissues just beneath it to promote relaxation, improve tissue extensibility, and increase blood flow. Hydrocollator packs fit this purpose perfectly: they are kept in a warm hydrocollator and applied to the skin, transferring heat primarily by conduction to superficial tissues. This sustained warmth helps decrease muscle guarding and pain and prepares muscles for stretching or manual therapy. They’re widely used in clinics because they provide consistent, easy-to-use, inexpensive warmth for about 15–20 minutes, with the added safety of a barrier between pack and skin and monitoring to avoid burns. Other options listed don’t deliver superficial heat in the same way: a cryotherapy bag cools tissue, electrical stimulation uses electrical energy rather than heat, and ultrasound delivers deeper heating that penetrates beyond superficial layers.