In the early 1990s, I went through the National Academy of Sports Medicine (NASM) program under Tom Purvis. It sparked something in me, a curiosity about movement and joint function that didn’t fully take root until years later. By 2013, I was testing clients’ range of motion (ROM) with a smartphone goniometer app, manually assessing shoulder flexion, ankle dorsiflexion, and spinal mobility.
Tom Purvis eventually became disillusioned with the “personal training mill” model and left NASM to found Resistance Training Specialist (RTS), a biomechanics-focused educational system for advanced trainers. Meanwhile, NASM has grown to become one of the most popular certification bodies in personal training. In recent years, it introduced its own Corrective Exercise Specialization that includes formal instruction in goniometry and posture-related assessments—nearly a decade after many of us had already begun testing ROM in the field.
Why ROM Testing Is the Missing Link for Most Trainers
Range of motion (ROM) is the foundation of functional movement. If a joint can’t move through its intended range, it can’t generate force safely or efficiently. Limited ROM leads to compensation, which can eventually cause pain or injury (1).
Goniometry provides a clear, trackable, objective way to evaluate joint mobility. It allows trainers to quantify deficits and design smarter programs. Unfortunately, many fitness certifications overlook it entirely or treat it as optional.
💡 Key Takeaway: ROM testing allows trainers to pinpoint dysfunction and prevent injuries before they happen.
Most Trainers Miss the Root of Dysfunction
Most trainers are taught to look at posture, strength, and flexibility, but not controlled joint mobility. Yet research shows that limited ROM, particularly in the hips, shoulders, and ankles, is tied to poor functional movement patterns and higher injury risk (2)(3).
Clients might squat poorly, not because of weakness or bad coaching, but because they physically can’t dorsiflex their ankles enough. Without measuring that joint angle, a trainer may misdiagnose the issue and reinforce bad habits.
💡 Key Takeaway: Poor movement is often caused by mobility restrictions, not strength deficiencies.
The Goniometer Changed My Practice in 2013
In 2013, I started using a goniometer app to assess joint angles. It was crude but effective. I could measure hip extension, thoracic rotation, or shoulder flexion in degrees. This gave me a baseline to track progress.
More importantly, it gave me data, real numbers that could justify programming decisions. The same shoulder that only flexed to 140° on Day 1? Now it moved to 160° after four weeks of mobility work. That was hard evidence that the training worked.
Even better? The data held up. Studies now show that smartphone goniometers are reliable and valid for measuring joint angles—comparable to traditional methods when used correctly (4).
💡 Key Takeaway: Tracking joint angles with an app is not just practical, it’s scientifically valid.
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NASM Caught Up—And That’s a Good Thing
In recent years, NASM and other certifying bodies have started teaching goniometry as part of posture and movement assessments. It’s a welcome shift, but it’s long overdue. Trainers must go beyond visual estimations and commit to measurable ROM tracking.
Assessing joint angles isn’t just for physical therapists. It should be part of every trainer’s toolkit. ROM determines exercise selection, movement safety, and client progress. Without it, you’re guessing.
💡 Key Takeaway: Visual observation is subjective. Goniometry brings precision and accountability to your assessments.
Why ROM Testing Needs to Go Mainstream
Mobility matters. Limited ROM leads to poor movement, injury, and decreased performance. By measuring it, trainers can pinpoint the real cause of dysfunction—whether that’s stiff ankles, tight hips, or poor thoracic rotation.
Even more importantly, ROM loss is a predictor of functional decline as we age. Research shows that older adults with limited mobility experience greater risk of disability and decreased quality of life (5). That’s a message personal trainers need to understand early in their careers.
💡 Key Takeaway: Measuring ROM isn’t just about workouts—it’s a window into long-term function and aging.
✏︎ The Bottom Line
Most trainers don’t test mobility because they were never taught to. But ROM testing is the missing link in effective program design, injury prevention, and client progress tracking.
You don’t need to become a physical therapist. But if you’re serious about results, you need to measure movement—not just strength or weight.
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Bibliography
- Norkin, C. C., and D. J. White. Measurement of Joint Motion: A Guide to Goniometry. F.A. Davis Company, 2016. http://library.unisel.edu.my/equip-unisel/custom/ebook_catalog/ebook/Measurementofjointmotionaguidetogoniometry5thed.pdf
- Mason-Mackay, A R et al. “The effect of reduced ankle dorsiflexion on lower extremity mechanics during landing: A systematic review.” Journal of science and medicine in sport vol. 20,5 (2017): 451-458. doi:10.1016/j.jsams.2015.06.006. https://pubmed.ncbi.nlm.nih.gov/26117159/
- Reiman, Michael P, and J W Matheson. “Restricted hip mobility: clinical suggestions for self-mobilization and muscle re-education.” International journal of sports physical therapy vol. 8,5 (2013): 729-40. https://pmc.ncbi.nlm.nih.gov/articles/PMC3811738/
- Soeters, Rupali et al. “Accuracy of a Smartphone Software Application Compared With a Handheld Goniometer for Measuring Shoulder Range of Motion in Asymptomatic Adults.” Orthopaedic journal of sports medicine vol. 11,7 23259671231187297. 31 Jul. 2023, doi:10.1177/23259671231187297. https://pubmed.ncbi.nlm.nih.gov/37533501/
- Cruz-Jentoft, Alfonso J et al. “Sarcopenia: revised European consensus on definition and diagnosis.” Age and ageing vol. 48,1 (2019): 16-31. doi:10.1093/ageing/afy169. https://pubmed.ncbi.nlm.nih.gov/30312372/
