The Effects of Cranial Laser Reflex Technique on Hamstring Flexibility, Strength, and Pain Pressure Threshold: a Pilot Study

First Visit: Subjects who met the inclusion criteria and gave consent completed a brief questionnaire on their activity level, history of hamstring injuries, and perceived hamstring tightness and were randomized to one of the following for the first treatment period: 1) active CLRT; or 2) sham laser.

After randomization, subjects were asked to complete the three functional hamstring tests: 90-90 Knee Extension Angle (KEA) to assess flexibility, handheld dynamometry (HHD) for strength, and pain pressure threshold (PPT).

Assessments. KEA: The 90-90 Knee Extension Angle test is a functional assessment designed to assess lower extremity flexibility and is considered the gold standard for hamstring length. The participant began in the supine position on a treatment table. The tested extremity (the right leg in each subject) was placed in a 90° hip and 90° knee position with the contralateral lower extremity placed flat on the table. A digital inclinometer was consistently placed at the level of the medial malleoli and the superior pole of the patella. The examiner maintained 90° of hip flexion. Pelvic position was monitored by palpation of the anterior superior iliac spine and lumbar spinous processes to maintain a neutral pelvic position. The examiner passively extended the knee to the point of a ''strong, but tolerable stretch," as reported by the subject. The examiner read the angle of the inclinometer and recorded the mean value of three attempts. A greater angle indicates greater degree of flexibility.

Hand held Dynamometry (HHD) is currently considered a reliable and valid measurement of peak muscle contraction. The subject began prone on the table with right leg bent to 90°. The tester placed the dynamometer (microFET2; Hoggan Health Industries, Salt Lake City, UT) at the heel of the participant and applied force to the heel, gradually increasing in 3 to 5 seconds. Participants was instructed to resist the applied force and maximally contract the hamstring muscle against the HHD device. The test ended once they are no longer able to resist the force and the leg begins to move (break point). The investigator recorded the mean value of three attempts.

Pain Pressure Threshold (PPT) is a reliable, accurate and valid method for measuring muscle pain sensitivity and response to treatment. The digital algometer (FDX, Wagner Instruments, Greenwich, CT) is a hand-held muscle tester with a range of 0-100 lbf that consists of a padded disc with a diameter of 0.5" attached to a microprocessor-control unit that measures peak force (pounds or kilograms). The unit has a digital readout for peak-applied pressure and provides a built-in calibration routine that verifies a valid calibration. In order to determine PPT, the researcher applied the tip of the algometer to a tender spot in the participant's hamstrings and increased the amount of pressure until the participant verbally informed the researcher when the sensation of pressure became pain. At this point the algometer was removed and the peak force recorded. The mean of three repeated measures was reported.