BESS Test Interpretation for ATs: Unlocking Balance Deficits in Concussion Evaluation
Accurate balance assessment is a cornerstone of effective concussion management. For athletic trainers on the front lines of injury care, interpreting the Balance Error Scoring System (BESS) and its widely-used variant, the modified BESS (mBESS), provides essential insight into postural stability deficits following head trauma. Understanding the application and limitations of these tools is critical not just for diagnosis, but also for monitoring recovery and guiding safe return-to-play decisions.
Understanding BESS and Its Clinical Value
The Balance Error Scoring System was developed as a clinical field test to evaluate postural stability under various stance conditions. A full BESS test includes six stances (double-leg, single-leg, and tandem) performed on both firm and foam surfaces, providing a comprehensive look at balance under increasingly challenging conditions. Errors such as stepping, stumbling, or opening the eyes during a closed-eye trial are counted, with higher scores indicating greater impairment.
The utility of BESS lies in its accessibility—it requires minimal equipment and can be administered quickly, making it ideal for sideline and clinic use. Yet, its effectiveness goes beyond convenience. Research shows that BESS is capable of detecting balance deficits post-concussion and following physical exertion.
A systematic review covering BESS use from 1999 to 2010 found moderate to good reliability, with stronger correlations to force-plate measures in the more challenging stances (particularly on foam surfaces) (source).
BESS vs. mBESS: What's the Difference?
The modified BESS (mBESS) is a streamlined version designed specifically for sideline evaluations and more streamline clinical balance testing. It eliminates the foam surface trials and focuses solely on the three stances (double-leg, single-leg, and tandem) on a firm surface. This simplification enhances practicality during acute assessment without significant sacrifice in diagnostic value.
In terms of sensitivity, mBESS may even outperform the full BESS in certain settings. A 2018 prospective observational study of collegiate athletes showed that mBESS demonstrated greater sensitivity (71.4%) compared to BESS (60.0%) in identifying acute balance impairments the day after concussion (source). Moreover, mBESS detected lingering balance deficits even when BESS scores had returned to baseline, suggesting that it may provide more persistent insight during follow-up evaluations.
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Recent data challenges the clinical value of the double-leg stance. A 2022 study examining over 600 baseline tests and 41 post-injury assessments among collegiate cheer and dance athletes found that omitting the double-leg stance (as in mBESS) resulted in minimal score differences, with negligible clinical impact (source).
Interpreting Errors: Clinical Considerations for Athletic Trainers
Error scoring in BESS requires attentive observation. Common errors include lifting hands off hips, opening eyes, stepping or stumbling, abduction or flexion of the hip beyond 30 degrees, and being out of position for more than five seconds. These errors can accumulate quickly, especially in the single-leg stance—the most challenging of the three stances.
Baseline testing is crucial to interpret post-injury scores accurately. Without individual pre-season baselines, comparisons rely on normative data, which may not capture athlete-specific balance nuances. Factors such as fatigue and lower extremity injury, can influence performance. As such, athletic trainers must contextualize test results within the broader clinical picture, including symptom reports, neurocognitive testing, and exertional tolerance.
Advancing the Science: Objective BESS Tools and Instrumented Systems
Using mobile technology, we’ve made it possible to conduct balance assessments like mBESS without extra gear or guesswork. Our platform captures postural stability data with built-in sensors—bringing objectivity and speed to sideline concussion evaluations.
Traditional BESS and mBESS relies on clinician judgment, which introduces potential for scoring variability. To improve objectivity, researchers have explored instrumented versions using force plates and motion sensors. One 2024 study on pediatric populations compared traditional BESS with a force plate–based version, confirming high reliability and highlighting sway variability across different stances and demographic groups (source).
Additionally, a 2017 study introduced a Kinect-based automated scoring system, achieving strong correlation with experienced raters (r = 0.93) and excellent test-retest reliability (ICC = 0.81). Such technology offers promising avenues for reducing subjective error and enhancing consistency in concussion evaluations (source).
Even portable force plate systems have demonstrated concurrent validity with traditional BESS, offering a bridge between field and lab-based assessments. In adolescents, these systems maintained strong reliability and showed alignment with clinician-scored outcomes (source).
Real-World Application: Balance Assessment in the Return-to-Play Process
Balance assessment plays a critical role throughout the concussion care continuum, not just immediately post-injury. The 6th International Consensus Statement on Concussion in Sport (Amsterdam, 2022) underscores the need for multimodal assessment tools and advocates for a gradual, stepwise return-to-play protocol. Balance, along with symptoms and cognitive function, must normalize before athletes progress to full activity. (source)
In this context, both BESS and mBESS offer value. In the acute phase, mBESS provides quick feedback to identify gross impairments. In the subacute and recovery phases, full BESS or instrumented systems can reveal persistent deficits that may warrant additional rehabilitation—particularly vestibular or neuromotor training.
Clinical Scenario: A High School Soccer Player Post-Concussion
Consider a 16-year-old forward who sustained a head collision during a weekend match. On Monday, the athletic trainer administers an mBESS and notes increased errors in the tandem and single-leg stances compared to the athlete’s preseason baseline. The athlete also reports dizziness and trouble focusing in class. Over the week, symptom tracking and repeated mBESS testing show gradual improvement, but residual balance errors persist.
In collaboration with the school’s concussion management team, the athletic trainer refers the athlete to a vestibular physical therapist. A targeted intervention plan is implemented. After two weeks, a repeat full BESS test reveals near-baseline scores, and the athlete completes a full exertion protocol without symptoms. A medical clearance follows, and the athlete safely returns to sport under continued monitoring.
Precision, Practicality, and Clinical Judgment
For athletic trainers, mastering BESS and mBESS interpretation is more than technical skill—it’s a matter of protecting athlete health. These tools, grounded in research and refined by clinical use, enable timely and informed decisions in concussion management. Whether used on the sideline or in follow-up care, their effectiveness depends on thoughtful integration with symptom tracking, cognitive assessment, and interdisciplinary communication.
While mBESS offers a streamlined solution for fast-paced environments, full BESS and objective balance tools bring added depth where needed. Balancing practicality with precision ensures that no signs are overlooked, especially in cases where symptoms persist or recovery stalls. As research continues to evolve, athletic trainers remain essential in applying these insights to real-world scenarios, always with the athlete’s safety at heart.
Reviewed by Kim Wyand, PT, DPT
Director of Customer Experience, Sway Medical
Dr. Kim Wyand is a licensed physical therapist and concussion education specialist with more than a decade of experience in outpatient orthopedic and neurological rehabilitation. On top of leading the customer experience team, Kim works closely with Sway's research team, ensuring the platform remains grounded in research and consistently aligned with evidence-based best practices. She leads the development of tools and resources that support over 13,000 clinicians and athletic programs in delivering high-quality concussion care.
