Movement amplitude on the Functional Re-adaptive Exercise Device: deep spinal muscle activity and movement control

Area of Science:

• Biomechanics and Exercise Physiology
• Musculoskeletal Rehabilitation
• Motor Control Research

Background:

• Low-back pain (LBP) is often associated with impaired motor control and atrophy of deep core muscles like the lumbar multifidus (LM) and transversus abdominis (TrA).
• The Functional Re-adaptive Exercise Device (FRED) is a novel intervention tool designed to promote automatic activation of LM and TrA through cyclical lower-limb movements.
• Previous research indicates FRED's potential for non-specific LBP management, but the impact of varying movement amplitudes on muscle engagement remains unexplored.

Purpose of the Study:

• To investigate the effects of different Functional Re-adaptive Exercise Device (FRED) movement amplitudes on the muscle thickness and movement variability of the lumbar multifidus (LM) and transversus abdominis (TrA).
• To provide an evidence-based foundation for optimizing FRED exercise prescription for individuals with low-back pain.

Main Methods:

• Ultrasound imaging was employed to measure the muscle thickness of the LM and TrA in eight healthy male volunteers during FRED exercise at four distinct movement amplitudes.
• Muscle thickness was normalized to resting values, and movement variability was quantified.
• Magnitude-based inferences were utilized for comparative analysis across different amplitudes.

Main Results:

• FRED exercise at all tested amplitudes significantly increased LM and TrA muscle thickness compared to rest, with increases of approximately 5 mm and 1 mm, respectively.
• Higher movement amplitudes resulted in greater increases in TrA thickness, as well as elevated muscle thickness variability for both LM and TrA.
• Increased movement variability was also observed with larger FRED amplitudes, suggesting a greater challenge to motor control.

Conclusions:

• All tested amplitudes of the Functional Re-adaptive Exercise Device (FRED) are effective in recruiting the lumbar multifidus (LM) and transversus abdominis (TrA) muscles.
• A progressive training approach is recommended, initiating with the smallest amplitude and gradually increasing it as participants achieve consistent movement speed to continually challenge the motor control system.