The Case Against Adductor Squeeze Tests
They say as your island of knowledge grows, so too the shoreline of your ignorance. It seems the older I get the more questions I have, and the fewer answers I’m able to give with great certainty. Twenty years ago, I entered the profession a young whipper snapper who had all the “right” answers, today I’m less certain than ever. A mentor of mine is fond of saying there is no shortage of information in this day and age. In fact, we’re swimming in a sea of it. However, most is noise. Your life preservers are to rely on great mentors and a solid foundation of first principal knowledge. What is first principal knowledge? First principal knowledge is a solid understanding of physics, biomechanics, physiology, programming, and psychology. These are the bedrocks of being a neo-generalist, and a serial specialist. In short, this understanding enables us to be better critical thinkers and coaches.
I recently had the opportunity to interview Dr. Mal McHugh on the High-Performance Hockey Podcast (to be released next Monday). He had authored a recent journal article with colleagues titled “Adductor Strains in Athletes” in the International Journal of Sports Physical Therapy. Mal and colleagues had published articles in 2001: “The Association of hip strength and flexibility with the incidence of adductor muscle strains in professional ice hockey players,” and a 2002: “ The effectiveness of a preseason exercise program to prevent adductor muscle strains in professional ice hockey players,” regarding adductor strains in high performance ice hockey. Mal has spent decades researching, and as a pragmatic practitioner testing 1000’s of athletes. A major Ah ha moment occurred to me after reading the text. It actually reached out and slapped me in the face. I chuckled to myself as I had failed to use my first principal knowledge in filtering out information. What information? Testing the adductor complex using common squeeze tests. According to Mal, the three key requirements for testing adduction strength are:
1. A comparison can be made between involved and non-involved sides
2. A comparison can be made between agonists (adductors) and antagonists (abductors)
3. The unit of measure enables comparison across populations
Here’s the slap! “Squeeze tests where both limbs contract maximally cannot be used to assess asymmetry in adduction strength between limbs. The laws of physics and neurophysiology invalidate such tests.” Laws? Physiology? What laws? What physiology? I had ignored my first principal knowledge. Mal had educated me to the obvious.
Newtons 3rd law: For every action, there is an equal and opposite reaction. “If one squeezes a dynamometer between the knees in the bent knee adduction squeeze test, or between the feet in the straight leg squeeze test, Newton’s third law dictates that the force on the right side will equal the force on the left side” ….” It follows that squeeze tests have not been shown to be effective at identifying strength deficit between limbs but have been effective at identifying athletes with groin and hip pathology versus healthy athletes.” If the goal is identifying asymmetries such as the adduction – abduction ratios, squeeze tests are not the solution.
Neurophysiology: The neurophysiological limitation in comparing strength between limbs while performing simultaneous max efforts with both limbs is called the bi-lateral deficit. “The bilateral deficit phenomenon is characterized by a lower force generated when two limbs perform a maximal effort bilaterally compared with the sum of the forces generated by the two limbs when performing the effort unilaterally. While the bilateral deficit has not been studied specifically for clinical assessment of weakness no studies have validated bilateral testing for identifying unilateral weakness.”
Just like that. Mal had opened my eyes to blind spots I never knew existed. First principal knowledge I had, but the critical thinking skills I failed to use. Mal proceeds in the 2023 article to suggest superior ways of measuring adductor strength and asymmetry, but the lessons he taught me moved well beyond physics, physiology, and pragmatic application. Think! Critically think! Understand your first principals. Use them as your filter. Come back to them often! Thanks Mal for the valuable lesson.
