Acute Effects of High-Intensity Laser Therapy on Pain, Muscle Stiffness, and Grip Strength in Healthy Adults (HILT)

High-intensity laser therapy will be administered using the Platinum 4 device (Summus Medical Laser) over the wrist flexor muscles of the dominant forearm, from the medial epicondyle of the humerus toward the wrist. All four wavelengths available on the device will be used. Each participant will receive one active treatment session, followed by a five-minute interval before the muscle-fatiguing exercise procedure. Both the participant and the therapist will wear appropriate protective eyewear.

High-intensity laser therapy will be administered using the Platinum 4 device (Summus Medical Laser) over the wrist flexor muscles of the dominant forearm, from the medial epicondyle of the humerus toward the wrist. All four wavelengths available on the device will be used. Each participant will receive one active treatment session, followed by a five-minute interval before the muscle-fatiguing exercise procedure. Both the participant and the therapist will wear appropriate protective eyewear.

Placebo high-intensity laser therapy will be administered over the wrist flexor muscles of the dominant forearm before the same muscle-fatiguing exercise procedure used in the active treatment condition. Each participant will receive one placebo treatment session, followed by a five-minute interval before the exercise procedure.

Sham high-intensity laser therapy will be administered over the wrist flexor muscles of the dominant forearm before the same muscle-fatiguing exercise procedure used in the active treatment condition. Each participant will receive one placebo treatment session, followed by a five-minute interval before the exercise procedure.

High-intensity laser therapy will be administered using the Platinum 4 device (Summus Medical Laser) over the wrist flexor muscles of the dominant forearm, from the medial epicondyle of the humerus toward the wrist. All four wavelengths available on the device will be used. Each participant will receive one active treatment session, followed by a five-minute interval before the muscle-fatiguing exercise procedure. Both the participant and the therapist will wear appropriate protective eyewear.

Placebo high-intensity laser therapy will be administered over the wrist flexor muscles of the dominant forearm before the same muscle-fatiguing exercise procedure used in the active treatment condition. Each participant will receive one placebo treatment session, followed by a five-minute interval before the exercise procedure.

Handgrip strength will be measured using a Baseline Lite handheld dynamometer on the dominant hand. Participants will be seated with the upper arm alongside the trunk, the elbow flexed to 90 degrees, the forearm in a neutral position, and the wrist in slight extension and ulnar deviation. Three maximal grip attempts will be performed at each assessment, and the highest value will be used for analysis. Changes from the pre-intervention baseline will be compared between active and placebo high-intensity laser therapy.

Muscle stiffness will be assessed using the MyotonPRO device at a predefined and marked anatomical measurement site over the wrist flexor muscles of the dominant forearm. The device applies a brief mechanical impulse to the skin and measures the tissue response to calculate muscle stiffness in newtons per meter (N/m). Higher values indicate greater stiffness. Changes from the pre-intervention baseline will be compared between active and placebo high-intensity laser therapy.