Muscle Oxygenation and Function in Breast Cancer Survivors

The NIRS sensor will be secured using a fiber-elastic band over the midline of the lateral deltoid muscle, immediately inferior to the acromion. Physiological variables, including the minimum, maximum, and change values of muscle oxygen saturation, will be recorded at rest and during and after the Six-Minute Pegboard and Ring Test. Muscle oxygenation will be expressed as the percentage of oxyhemoglobin relative to the sum of oxyhemoglobin and deoxyhemoglobin. Bilateral musce oxygenation of the middle portion of the deltoid muscle will be assessed before, during, and after the test. During exercise, an inability to adequately meet the increased oxygen demand of the working muscle may result in reduced SmO₂ levels. SmO₂ is influenced by shifts in the hemoglobin dissociation curve as well as by other chemical and neural factors.

The strength of the middle and anterior portions of the deltoid muscle will be assessed using a hand-held dynamometer. The test will be performed with the participant in an unsupported sitting position, with the shoulder positioned at 90° of abduction and 90° of flexion, in neutral rotation, and with the elbow fully extended. Resistance will be applied using the dynamometer over the distal humerus, and the participant will be instructed to attempt to elevate the arm with maximal force. Three measurements will be obtained, and the highest value will be recorded in Newtons (N).

Upper extremity functional exercise capacity will be assessed using the Six-Minute Pegboard and Ring Test. Participants will sit on an adjustable chair in front of a pegboard consisting of two lower horizontal bars positioned at shoulder height and shoulder width, one on the right and one on the left, and two upper bars positioned 20 cm above the lower bars. Each upper bar will contain 10 rings. Participants will be instructed to transfer the rings from the lower bars to the upper bars and then back to the lower bars as quickly as possible, using both arms simultaneously. If a participant requires rest, they will be permitted to rest while the test duration continues, with instructions to resume the test as soon as possible. The number of rings transferred during the 6-minute test will be recorded. Two rings removed and placed simultaneously will be counted as two rings.Blood pressure, heart rate, and peripheral oxygen saturation will be recorded before and immediately after the test.

Upper extremity disability will be assessed using the Disabilities of the Arm, Shoulder and Hand Questionnaire-Quick Version (QuickDASH). The Turkish version of the QuickDASH, which has been demonstrated to be valid and reliable, will be used. The QuickDASH consists of 11 items, with each item scored on a 5-point scale ranging from 1 to 5 (1 = no difficulty, 2 = mild difficulty, 3 = moderate difficulty, 4 = severe difficulty, and 5 = unable to perform). The questionnaire assesses pain severity, activity-related pain, tingling, weakness, stiffness, difficulty performing physical activities due to upper extremity problems, and the impact of upper extremity problems on social activities, work, and sleep.

The QuickDASH score ranges from 0 to 100, with higher scores indicating greater disability (0 = no disability; 100 = maximum disability). A score of ≥20 indicates clinically significant functional impairment.