Which of the following techniques is commonly used in physical therapy?

Hydrotherapy is a technique commonly used in physical therapy as it involves the use of water for pain relief, rehabilitation, and physical therapy. This approach can improve a patient's mobility, strength, and overall recovery by utilizing the buoyancy and resistance of water, which can facilitate easier movement and support in exercises. The warmth of the water can also promote relaxation and improve circulation, making it beneficial for various musculoskeletal and neurological conditions.

The other options, while beneficial in their own contexts, are not primarily associated with physical therapy. Psychological counseling focuses on mental health and emotional support, cognitive therapy centers on addressing thought patterns and behaviors, and art therapy uses creative processes for expression and healing. However, these approaches are more aligned with psychological or expressive therapies rather than the physical aspects of rehabilitation and recovery found in physical therapy practices.