I have the fortunate opportunity to work with many different diagnoses in my clinic. While my heart will always be in the shoulder and upper extremity (and thus so is my caseload), I would consider the hip a close cousin to the shoulder and thus is a close second on my list of favorite things to treat. Today we discuss the information I take into account when treating nearly any hip condition- from hip arthroscopy, impingement, osteoarthritis, to gluteal repairs.
Dozens of studies on the electromyographical (EMG) activity of various muscles in the body have been published in recent years, and the nerd in me finds it all fascinating. From this EMG research, we can identify a muscle's "maximal volitional isometric contraction" (MVIC), a percentage of a muscle's 1 rep max (1RM). This research can show us how hard a muscle is working relative to its potential and in comparison to other muscle groups around it during a single movement. EMG activity is typically gathered through live wire or surface electrodes- something I'm grateful that someone else volunteers to do!
Below you will find our current evidence for gluteus maximus, gluteus medius, and hamstring with various exercises. Undoubtedly, there is more evidence here on gluteus medius activation and the remainder regarding hamstring, iliopsoas, and TFL recruitment exists out there, but this should help get you started...
How I use this information varies. I use NMES on the gluteus medius a lot in the initial phases of rehab. I typically progress a patient from low to moderate to high MVIC relatively quickly because I know that the NMES is firing the muscle during the movement I have the patient perform. When we transition away from NMES, I drop the MVIC back down until the patient's own voluntary muscle memory kicks in more efficiently (one might say I have trust issues...). For a patient with hip impingement, I want to emphasize pelvic control, and then increase the gluteal to iliopsoas ratio. For a gluteal tendon repair, I completely avoid the higher MVIC activities until appropriate healing has happened- but this research tells me what I CAN do in the meantime. Furthermore, if someone is a "Master Cheater", I can pick exercises that target the muscle they don't use and minimize their compensation with another muscles (ie. hamstring versus gluteus maximus recruitment, or gluteus medius versus TFL).
In the shoulder, exercises with 0-15% MVIC are considered passive range of motion (ROM), 16-21% are active-assisted ROM, 22-29% are active ROM, and 30-49% are resisted/strengthening. We don't currently have a consensus on this to translate for the hip. However, some studies categorize exercises into low (0% to 20%), moderate (21% to 40%), high (41% to 60%), and very high (> 61%). Nonetheless, we can still use this information to make educated decisions about the activities we're giving our patients at a particular point & time. And obviously, these numbers will fluctuate with added resistance/weight.
Disclaimer: any activity progression should be based on the patient's appropriate performance and tolerance of the activity; EMG research is merely another tool to guide our decision-making.
References:
1. Ebert JR, et al. A Systematic Review of Rehabilitation to Progressively Load the Gluteus Medius. J Sport Rehabil. 2017 Sep;26(5):418-436
2. McCurdy K, et al. Gluteus Maximus and Hamstring Activation During Selected Weight-Bearing Resistance Exercises. J Strength Cond Res. 2018 Mar;32(3):594-601
3. Hartman JP, et al. Electromyographic analysis of gluteus maximus and hamstring activity during the supine resisted hip extension exercise versus supine unilateral bridge to neutral. Physiother Theory Pract. 2017 Feb;33(2):124-130.
4. Haverkamp R, et al . Building A Better Gluteal Bridge: Electromyographic Analysis of Hip Muscle Activity During Modified Single Leg Bridges. Int J Sports Phys Ther. 2017 Aug;12(4):543-549.
5. Contreras B, et al. A Comparison of Gluteus Maximus, Biceps Femoris and Vastus Lateralis Electromyography Amplitude in the Parallel, Full, and Front Squat Variations in Resistance-Trained Females. J Appl Biomech. 2016 Feb;32(1):16-22.
6. Distefano LJ, et al. Gluteal muscle activtion during common therapeutic exercises. J Orthop Sports Phys Ther. 2009 Jul;39(7):532-40. 7. Boren K, et al. Electromyographic analysis of gluteus medius and gluteus maximus during rehabilitation exercises. Int J Sports Phys Ther. 2011 Sep;6(3):206-23. 8. Macadam P, et al. An Examination of the Gluteal Muscle Activity Associated with Dynamic Hip Abduction and Hip External Rotation Exercise: A Systematic Review. Int J Sports Phys Ther. 2015 Oct;10(5):573-91.
