The Immediate Effects of Hamstring Stretching Alone or Combined With Myofascial Release of the Hamstring Muscle on Masseter Muscle Activity, Pressure Pain Threshold, Active Mouth Opening, Hamstring Flexibility, and Forward Head Flexed Posture in Recreationally Active Participants: A Randomized, Double-Blind, Controlled Trial Study

Pressure pain threshold

时间窗: 4 weeks

The pressure pain threshold was measured using a mechanical pressure algometer (model Baseline® Dolorimeters - Fabrication Enterprises Inc) with a contact head of 1 cm2 area.The participant was positioned lying supine while the pressure pain threshold of the masseter muscle's central trigger point was assessed on both sides. Pressure was applied perpendicular to the masseter, gradually and continuously at a rate of about 1 kg/cm/s. The participants were requested to let the examiner know as soon as pain started to be felt. With a 2-min rest period between each experiment, three pressure pain threshold measures were taken. The average value of the three trials was calculated and used in the analysis.

Maximum Active Mouth Opening

时间窗: 4 weeks

A tape measure was used to determine the maximum active mouth opening (MMO). The participants were measured while laying flat on their back with the head resting on a table, the cervical spine in a neutral position, the knees slightly bent, and the upper limbs lying parallel to the torso. The subjects were instructed to open the mouth as wide as possible without inflicting discomfort. The distance between the upper and lower central incisors was measured and recorded in millimetres. For the primary analysis, the mean value of three trials was calculated.

superficial masseter muscles EMG activity

时间窗: 4 weeks

For each subject, EMG activity was recorded from the left and right superficial masseter muscles using a multichannel EMG device.

Tragus Wall Distance

时间窗: 4 weeks

Tragus wall distance measurement was used to evaluate spinal mobility. The participants were instructed to stand with their feet shoulder-width apart, and heels, hips, and shoulders against the wall. Then, before each measurement, the participants were asked to "stand with good posture, look straight ahead, and hold this position until the measurement is taken". The participants were then told to take a self-selected position for the head and neck that reflected their perception of "good posture". The distance between the tragus and the wall was measured and the participant was repositioned away from the wall before each measurement

Hamstring Flexibility

时间窗: 4 weeks

The Maximal Hip Flexion Active Knee Extension (MHFAKE) Test, which is an adapted active knee extension test, was performed to evaluate the hamstring flexibility of the participant. The subject was instructed to keep the hip in maximal flexion by clutching the thigh to the chest, with the hands holding the opposite elbows, and then to actively extend the knee until reaching the point of maximal tolerable stretch of the hamstring muscle or the point where pain was reported. The contralateral leg was fixed by the clinician. The angle of inclination of the mid-shin was measured at the endpoint of maximal stretch with the handheld inclinometer.