Recent smartphones, such as the iPhone, are often equipped with an accelerometer and magnetometer that, through software applications, can perform various inclinometric functions. Although many of these applications are intended for recreational use, they have the potential to measure and quantify range of motion.


The purpose of this study was to estimate the intra and inter-rater reliability as well as the criterion validity of the clinometer and compass applications of the iPhone in the assessment of the cervical range of motion in healthy participants.

Study Conclusion:

When compared to the gold standard (CROM), the iPhone applications showed moderate to good validity as an assessment tool. There was also good intra-rater reliability and but lower inter-rater reliability.


The ability to carry an accurate mobile gyroscope and accelerometer in a mobile device has implications for a range of specialties including orthopedics and physiatry. This study agrees with a number of other studies that show mobile devices can be relatively accurate when compared to existing measuring standards. Future work in the field of cervical range of motion should focus on measurements in pathological scenarios.


  • The sample consisted of 28 healthy participants (9 men and 19 women) aged from 19 to 43 years old (mean ± SD: 23 ± 6)
  • Two examiners measured cervical range of motion of each participant twice using the iPhone (for the estimation of intra and inter-reliability) and once with the CROM (for the estimation of criterion validity).
  • An iPhone 3GS and an iPhone 4 were used for the study.
  • The application used to measure the cervical ROM in frontal and sagittal planes is Clinometer. The application used to measure the cervical ROM in horizontal plane is Compass, software already integrated in the iPhone.
  • Estimates of reliability and validity were then established using the intraclass correlation coefficient (ICC).

Screen Shot 2013-11-01 at 01.02.59


  • There was moderate intra-rater reliability for each movement (ICC = 0.65-0.85) but a poor inter-rater reliability (ICC < 0.60).
  • For the criterion validity, the ICCs are moderate (>0.50) to good (>0.65) for movements of flexion, extension, lateral flexions and right rotation, but poor (<0.50) for the movement left rotation.
  • The findings of this study showed that when the cervical ROM is measured with the iPhone by the same examiner (intra-rater reliability), similar results can be expected from one session to the next.

Article Name: Reliability and criterion validity of two applications of the iPhone to measure cervical range of motion in healthy participants
Authors: Yannick Tousignant-Laflamme, Nicolas Boutin, Alexandre M Dion and Carol-Anne Vallée
Journal Published: Journal of NeuroEngineering and Rehabilitation
Date Published: Received: 4 July 2012 / Accepted: 14 June 2013 / Published online: 5 July 2013
Citation: Tousignant-Laflamme et al.: Reliability and criterion validity of two applications of the iPhoneTM to measure cervical range of motion in healthy participants. Journal of NeuroEngineering and Rehabilitation 2013 10:69.