The Role of Isometric Exercise on Pain Modulation and Muscle Oxygenation in Individuals With Rheumatoid Arthritis

Pain Tolerance Assessment

Time Frame: Day 1

Gradual pressure will be applied to the volar (palm side) region of the non-dominant forearm using a pressure gauge (initial intensity-0 kPa, rate-30 kPa/s, 3 repetitions, interval between stimuli-45 seconds). The maximum pressure that participants can tolerate will be recorded as the pressure is increased. The average of 3 consecutive measurements will be taken. The tip of the gauge will be shifted 0.5 cm between repetitions to avoid changes in skin sensitivity. Pain was assessed using the Visual Analog Scale (VAS). The VAS consists of a 10-cm horizontal line ranging from 0 to 10, where 0 indicates "no pain" and 10 indicates "the worst pain imaginable." Total scores range from 0 to 10, with higher scores indicating greater pain severity (worse outcome).

Pressure Pain Threshold Assessment

Time Frame: Day 1

Based on the modified limits method, a pressure algometer will be used to apply gradual pressure to the volar (palm-side) region of the non-dominant forearm (initial intensity-0 kPa, velocity-30 kPa/s, 3 repetitions, interval between stimuli-45 seconds). Participants will inform the investigator when they first perceive pain. The pressure pain threshold will be taken as the average of 3 consecutive measurements. The algometer tip will be shifted 0.5 cm between repetitions to avoid changes in skin sensitivity. Pain was assessed using the Visual Analog Scale (VAS). The VAS consists of a 10-cm horizontal line ranging from 0 to 10, where 0 indicates "no pain" and 10 indicates "the worst pain imaginable." Total scores range from 0 to 10, with higher scores indicating greater pain severity (worse outcome).

Conditional Pain Modulation Assessment

Time Frame: Day 1

A conditioning pressure stimulus will be applied to the non-dominant upper extremity, and the pressure pain threshold will be measured in the dominant upper extremity. The non-dominant hand will be immersed up to the wrist in a bucket of water at 37°C for 10 seconds to induce conditioning. The patient will then be asked to immerse their hand in water adjusted to 46°C for 30 seconds. This temperature has been used in many previous studies. During this time, the pressure pain threshold will be measured on the volar portion of the forearm of the contralateral extremity. Pain was assessed using the Visual Analog Scale (VAS). The VAS consists of a 10-cm horizontal line ranging from 0 to 10, where 0 indicates "no pain" and 10 indicates "the worst pain imaginable." Total scores range from 0 to 10, with higher scores indicating greater pain severity (worse outcome).