Effects of Trunk Angle in the Sitting and Standing Postures on the Static Flexion Relaxation Phenomenon

Abstract

The effects of different postures on the static flexion relaxation phenomenon were compared using electromyography, to clarify whether the angles for the activation and relaxation of the spinal muscles are different. [Subjects and Methods] Thirty healthy males maintained several different trunk inclination angles while standing and sitting. The muscle activities were measured and compared among the different postures and the different trunk angles: 0, 10, 20, 30, 40, 50, 60, and maximum forward leaning. The thoracic and lumbar erector spinae, multifidus, gluteus maximus, and biceps femoris were the target muscles. [Results] Muscle activities increased with increasing forward inclination angle, but at low inclination angles in the sitting position, the activities of the multifidus and erector spinae were constant. Between the postures, trunk muscle activities became significantly lower in the sitting position than in the standing position with increasing inclination. [Conclusion] Compared to standing, muscle activities at low inclination angles have low, constant values.

Effects of movement from a postural maintenance position on lumbar hemodynamic changes

“…In our study, the muscle activity in the sitting condition was more constant at shallower flexion angles than that in the standing condition during the flexion–extension exercise. These results are consistent with our earlier study 1 ) and are most likely due to greater increases in muscle extension and activity in MF compared to that of LES, with an increased trunk flexion angle while standing. There was, therefore, increased internal muscle pressure in the MF, which resulted in decreased muscle blood flow, increased muscle oxygen demand due to ischemia, and decreased Oxy-Hb due to oxygen consumption.…”

“…In accordance with earlier studies 1 , 2 ) , the first exercise task (flexion-extension exercise) involved the subject gradually moving the trunk, 10° at a time, from an upright, resting trunk position of 0° flexion, as measured by an electric goniometer (NorAngle, Noraxon, Scottsdale, AZ, USA), to a position of maximum flexion, and then returning to a position of 0° flexion (re-upright) by extending the trunk. The second task (extension-flexion exercise) involved the subject gradually moving the trunk, 10° at a time, from an upright position to a position of maximum trunk extension, and then returning to a position of 0° flexion (re-upright) by flexing the trunk.…”

“…In the current super-aging society, work-related lower back pain is common in caregivers who are frequently required to adopt a flexed posture with the trunk tilted forward. In previous studies, we examined lower back muscle activity and tissue stiffness during trunk flexion while standing and sitting and found more constant muscle activity and increased tissue stiffness at shallower flexion angles among participants in seated positions compared to those of participants in standing positions 1 , 2 ) . Excessive increase in tissue stiffness leads to impaired blood flow, and the resultant lumbar ischemia is associated with lower back pain.…”

Is the flexion relaxation ratio a reliable, valid, and responsive measure for individuals with and without non-specific spine pain? A systematic review and meta-analysis

“…The full text for two studies could not be retrieved 10,11 . 9 non-English studies were retrieved but not screened due to limited access to translation services 10,[12][13][14][15][16][17][18][19] . One study appeared to meet the inclusion criteria but was excluded because we could not confirm it was an independent sample of participants from a previously included study 20 .…”