Abstract ▼ AI-Helper

The flexion-relaxation phenomenon (FRP) refers to erector spinae (ES) muscle relaxation in electromyograph (EMG) readings near full flexion during trunk forward bending. FRP occurrences can be analyzed using the methods of visual inspection, statistical, threshold, and ratio. There have been many st...

The flexion-relaxation phenomenon (FRP) refers to erector spinae (ES) muscle relaxation in electromyograph (EMG) readings near full flexion during trunk forward bending. FRP occurrences can be analyzed using the methods of visual inspection, statistical, threshold, and ratio. There have been many studies on the FRP of the ES muscles. Recently, it was reported that an activation pattern similar to flexion-relaxation (FR) is shown by the hamstring muscles. Hamstring-muscle length may be related to specific pelvic and trunk movements. Also, hamstring-stretching exercises are usually used to change lumbar spine and pelvic movements in the clinic. So, we investigated the effects of hamstring-stretching exercises on the FR ratio of the hamstring and ES muscles, and lumbopelvic kinematics during forward bending in subjects with hamstring-muscle shortness.
Subjects who had a popliteal angle of greater than 20 were recruited using the active knee extension (AKE) test. They were randomly divided into the experimental group (n=15) and a control group (n=15). Passive stretching exercises were performed by the principal investigator on the hamstring muscles, three times a week for four weeks and the subjects themselves also performed active hamstring-muscle stretching exercises in the same manner as the AKE testing protocol, for 10 minutes daily in the intervention group. Data were collected using the EMG system, which was synchronized with a motion analysis system.
There was no significant difference in baseline measurement between the groups (p>.05). After the stretching exercises, in the experimental group, the hamstring-muscle activity significantly decreased during the full-flexion phase compared to the baseline data (p<.05), and the hamstring-muscle activity in the experimental group showed a significantly greater decrease than that of the control group during the full-flexion phase (p<.05). There was a significant increase in the FR ratio of the hamstring muscle in the experimental group (p<.05). The FR ratio of the hamstring muscle in the experimental group showed a significantly greater increase than that of the control group (p<.05). In addition, the subjects who used the hamstring-stretching exercises had significantly greater pelvic flexion during forward-bending movement (p<.05). The pelvic flexion movement in the experimental group showed a significantly greater increase than that of the control group (p.05).
The results of this study suggest that stretching exercises of the hamstring muscles might cause changes in people’s hamstring-muscle activity and lumbopelvic kinematics during forward-bending movement.

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