PREPRINT SCIENCE & TECHNOLOGY Journal homepage: http://www.pertanika.upm.edu.my/ Article history: Received: 17 September 2021 Accepted: 10 January 2022 Published: 18 March 2022 ARTICLE INFO E-mail addresses: iskandarasraf@gmail.com (Muhammad Iskandar Asraf) linoby@uitm.edu.my (Adam Linoby) azam5713@gmail.com (Muhammad Azamuddin Rodzi) drmuhammadmahadi@gmail.com (Muhammad Mahadi Abdul Jamil) rozita.abdlatif@uitm.edu.my (Rozita Abdul Latif) miqbalkhan0713@gmail.com (Iqbal Norhamazi) *Corresponding author ISSN: 0128-7680 e-ISSN: 2231-8526 © Universiti Putra Malaysia Press DOI: https://doi.org/10.47836/pjst.30.2.39 Validation and Usability Evaluation of Mobile Application to Monitor Real-Time Exercise Heart Rate Zone Muhammad Iskandar Asraf 1 , Adam Linoby 2 *, Muhammad Azamuddin Rodzi 1 , Muhammad Mahadi Abdul Jamil 3 and Rozita Abdul Latif 1 and Iqbal Norhamazi 1 1 Faculty of Sports Science and Recreation, Universiti Teknologi MARA, 40460 UiTM, Shah Alam, Selangor, Malaysia 2 Faculty of Sports Science and Recreation, Universiti Teknologi MARA, Negeri Sembilan Branch, Seremban Campus, 70300 UiTM, Seremban, Negeri Sembilan, Malaysia 3 Faculty of Electronic Engineering, Universiti Tun Hussein Onn Malaysia, 86400 UTHM, Parit Raja, Johor, Malaysia ABSTRACT A mobile application to monitor heart rate (HR) during an exercise called Chromozone was developed to enable a user to regulate exercise intensity using a color-coded system rather than numerical display in the most conventional device. In this study, the agreement of HR from Chromozone was compared against the HR dataset from a clinically accepted electrocardiogram (ECG) on diferent exercise intensity and to assess its reliability by intra- day repeated assessments. Additionally, the usability aspect of the Chromozone smartphone application was also assessed. Forty-two participants underwent self-selected exercise intensities (based on individual HR reserve) included for 5-min followed by a cool-down period (3-min). A 20-min rest period was given to the participant before repeating the same exercise protocol two more times. Chromozone was found to generate excellent criterion-concurrent validity (r = 0.998, p < 0.001) and acceptable bias of 1.96 bpm (Limits of Agreement; LoA: 3.07 to -3.51) for relative and absolute agreement, respectively. Similarly, relative (intraclass correlation coefcient test: 0.998, p < 0.001) and absolute (within-subject coefcient of variation: 1.95 ± 1.4%) reliability using Chromozone application shows an excellent consistency. Additionally, this study also