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. Participants were allowed to use their own lifting footwear.