2, 4 – 13 However, some studies 14, 15 suggest no difference between PNF and other stretching techniques. Previous studies support greater increases in ROM with PNF stretching techniques than with passive, static, or ballistic stretching methods. The literature is inconclusive regarding which stretching method is best for increasing muscle length. In a previous study using a static stretching protocol, hamstring flexibility increased significantly but only remained increased for 3 minutes after stretching.
This study demonstrated that hamstring flexibility remains significantly increased after the modified hold-relax stretching protocol for 6 minutes. The 15 subjects assigned to the control group lay supine on the evaluation table for 5 minutes, the approximate time it took to stretch the experimental group.
All stretching was performed on the right lower extremity. This sequence was repeated 5 times on each subject in the experimental group. The stretch was held for another 7 seconds. The investigator then passively stretched the muscle until a mild stretch sensation was reported. After the contraction, the subject relaxed for 5 seconds. Next, the subject maximally isometrically contracted the hamstrings for 7 seconds by attempting to push his leg back toward the table against the resistance of the investigator (Figure (Figure2). For each stretch, the investigator passively stretched the hamstrings until the subject first reported a mild stretch sensation and held that position for 7 seconds. Predetermined time intervals for stretching, contracting, and relaxing were used to standardize stretching methods for the stretching group. 4, 20 This modified hold-relax stretch was performed with no hip rotation. The 15 subjects assigned to the stretching group received visual and verbal instruction in performing the modified hold-relax stretch. Subjects were randomly assigned to either the control or the stretching group. The investigator recorded protractor measurements of AKE on the right side. The protractor was adjusted to read 90° when the knee was flexed to 90°. 19 A gravity-assisted protractor (Empire Level Manufacturing Co, Mukwonago, WI) was attached 2.54 cm below the right fibular head by a hook-and-loop strap. Throughout the AKE procedure, the left hip remained at 0° of flexion. The investigator ensured that the distal anterior thigh maintained contact with the cross-bar for all AKE measurements (Figure (Figure1). A polyvinylchloride pipe frame served as a cross-bar so that 90° hip flexion was maintained throughout AKE measurements. Subjects were positioned supine on an examination table with the hip flexed to 90° as measured by a goniometer (Rolyan Medical Products, Menomonee Falls, WI). With subjects lying on their left sides, the greater trochanter of the right femur, lateral femoral epicondyle, and lateral malleolus of right fibula were identified and marked with a black felt-tip marker to help ensure proper alignment for goniometric measurements. Thus, the purpose of our study was to measure the duration of hamstring flexibility gains after a 1-time hold-relax stretching protocol.
Relax time series#
18 Previous research has not focused on the duration of flexibility gains after a single, same-day series of hold-relax stretches. A 1-time session of 4 consecutive 30-second static stretches has been shown to increase flexibility for 3 minutes after the stretching protocol. However, the duration of flexibility gains after a single stretching session has received limited study. 13, 16, 17 These studies have shown that frequency and duration of static, ballistic, and PNF stretches affect ROM gains. Regardless of the techniques used, flexibility gains in the hamstring muscles have been demonstrated after a multiple-day stretching program.
2, 4 – 13 However, other studies have reported that the results achieved with static and ballistic stretching techniques are comparable with those achieved with PNF stretching techniques. 2 – 12Ī number of previous studies have demonstrated that proprioceptive neuromuscular facilitation (PNF) stretching techniques produce greater increases in ROM than passive, static, or ballistic stretching methods. 1 Several stretching techniques are used to increase joint range of motion (ROM). Athletes are often given stretching protocols to improve their flexibility. Stretching is important for reducing injury and improving performance in sports and for overall physical fitness. Flexibility is a key component for injury prevention and rehabilitation.
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