Patients undergoing total hip replacement often have weak hip abductor muscles before and after surgery. One of the most common hip exercises is sidelying hip abduction using an ankle weight. While this may be an effective exercise to activate the gluteus medius muscle, open-chain, non-weight bearing hip abduction is not specific to the function of the gluteus medius as a pelvic stabilizer in single-leg stance. Resisted lateral walking with a Thera-Band® Band Loop or Tubing with Cuffs is an example of such a closed-chain exercise as the patient steps away from the involved leg.
Researchers at the University of Kentucky evaluated electromyographic (EMG) levels of 4 exercises in total hip patients between 7 and 32 weeks post-operative. Dr. Cale Jacobs and colleagues were interested to see if there was a progression of muscle activation to guide clinical decisions about hip abduction exercise prescription. They published their findings in the Journal of Arthroplasty. The 4 exercises included 2 non-weight bearing and 2 weight-bearing exercises:
- Standing hip abduction with cuff weight at 1% of bodyweight, lifted to 30 degrees
- Sidelying hip abduction with cuff weight at 0.5% of bodyweight, lifted to 50% of leg length
- Standing hip abduction with uninvolved leg to 30 degrees
- Lateral walk with Thera-Band resistance band attached with extremity straps around ankle
Researchers used a level of Thera-Band resistance that created the same torque as the standing hip abduction exercise (1% body weight) with stretch on the band at 50% elongation. The researchers used this chart of Thera-Band elastic resistance pull forces to prescribe the appropriate color of band.
Both the sidelying abduction and weight-bearing standing abduction with the other leg produced an average of 67% maximum voluntary isometric contraction (MVIC). The Thera-Band resisted lateral walk exercise produced an average of 63% MVIC and the non-weight bearing standing abduction produced 58%. There was no significant difference in activation between exercises, indicating no clear order of exercise progression. The researchers suggested these exercises can be used interchangeably, particularly when balance impairment or postural position may be an issue.
In conclusion, non-weight bearing exercises involving open-chain hip abduction provide no additional benefit of gluteus medius activation compared to more functional closed-chain exercises. Thera-Band loop resisted walking provides moderate (>60% MVIC) of gluteus medius activation in post-operative total hip replacement patients.
REFERENCE: Jacobs CA, et al. Electromyographic analysis of hip abductor exercises performed by a sample of total hip arthroplasty patients. J Arthroplasty. 2009 Oct;24(7):1130-6. Epub 2008 Aug 30.