Author(s): LLEWELLYN, H., CUCATO, G., WILHELM NETO, E., AUDSLEY, S., ONEILL, P., Institution: NORTHUMBRIA UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 489

INTRODUCTION:
Isometric wall squat has been prescribed as a simple and accessible form of lower-limb exercise. Knee joint angle can be used to prescribe wall squat positioning, as an absolute indicator of exercise intensity. However, protocol delivery varies considerably between studies, with some using goniometry and others relying on participant-adjusted knee angle positioning. While goniometry is considered gold standard for joint angle measurement, it requires two hands for alignment, anatomical landmark identification, and maintaining position during measurement. These challenges can contribute to inter-tester variability and measurement error. Establishing baseline positions using goniometry can be time-consuming and uncomfortable, particularly at acute angles in untrained populations. As limb length remains relatively consistent in healthy adults following skeletal maturity (~18 years females, ~21 years males), algorithms using anthropometric measurements may offer a standardised alternative. This study validated a novel squat height calculator algorithm against goniometry for measuring knee angle during wall squats.
METHODS:
Twenty-one healthy adults (12 male, 9 female; age 28.3±10.3 years) completed a single testing session. Thigh length (greater trochanter to lateral femoral epicondyle) and lower leg length (lateral tibial condyle to floor) were measured. Participants performed wall squats at five target knee angles (135°, 125°, 115°, 105°, 95°) in two conditions: (1) goniometer-adjusted positions (reference standard), and (2) algorithm-derived positions. Agreement was assessed using intraclass correlation coefficient (ICC 2,1) and Bland-Altman analysis. Systematic bias was evaluated using the Wilcoxon signed-rank test. Clinical accuracy thresholds were set at ±3° and ±5°.
RESULTS:
The algorithm demonstrated excellent agreement with goniometer measurements across 105 paired observations (ICC=0.995, 95%CI [0.993-0.997]; r=0.996). Mean bias was minimal (-0.31°±1.34°) with 95% limits of agreement from -2.94° to +2.31°. No proportional bias was detected across the knee angle range (r=-0.019, p=.851). The Wilcoxon signed-rank test revealed a statistically significant but clinically negligible difference (Z=-2.378, p=.017; Cohen's d=0.23). Measurement error was low (SEM=1.00°; MDC₉₅=2.80°). Clinical accuracy was 99.0% within ±3° and 100% within ±5°. Accuracy within ±3° was 95.2% at 135° and 100% at all other angles.
CONCLUSION:
The squat height calculator algorithm provides an accurate, practical method for prescribing knee angle-specific wall squats without specialised equipment. With excellent agreement to goniometry (ICC=0.995) and 99% clinical accuracy within ±3°, this tool addresses protocol standardisation challenges and enables reliable home-based isometric exercise prescription. Future research should evaluate its application in clinical populations and home-based exercise interventions.