Reliability of the Coach’s Eye goniometer application during squat exercise

This study examined the test re-test, intrarater and interrater reliability of joint kinematics from the Coach’s Eye smartphone application. Twenty-two males completed a 1-repetition maximum (1-RM) assessment followed by 2 identical sessions using 5 incremental loads (20%-40%-60%-80%-90% 1-RM). Peak flexion angles at the hip, knee, and ankle joints were assessed using 1 experienced practitioner and 1 inexperienced practitioner. The acceptable reliability thresholds were defined as intraclass correlation coefficient (ICC) (r) > 0.70 and coefficient of variation (CV) ≤ 10%. The test re-test reliability of peak hip and knee flexion were reliable across 20-90% 1-RM (r > 0.64; CV < 4.2%), whereas peak ankle flexion was not reliable at any loaded condition (r > 0.70; CV < 20.4%). No significant differences were detected between trials (p > 0.11). The intrarater reliability was near perfect (r > 0.90) except for peak ankle flexion (r > 0.85). The interrater reliability was nearly perfect (r > 0.91) except for hip flexion at 80% 1-RM and ankle flexion at 20% (r > 0.77). Concludingly, the Coach’s Eye application can produce repeatable assessments of joint kinematics using either a single examiner or 2 examiners, regardless of experience level. The Coach’s Eye can accurately monitor squat depth.