Validity of simplified, calibration-less exercise intensity measurement using resting heart rate during sleep: a method-comparison study with respiratory gas analysis

Hirotaka Matsuura; Masahiko Mukaino; Yohei Otaka; Hitoshi Kagaya; Yasushi Aoshima; Takuya Suzuki; Ayaka Inukai; Emi Hattori; Takayuki Ogasawara; Eiichi Saitoh

doi:10.1186/s13102-019-0140-x

Validity of simplified, calibration-less exercise intensity measurement using resting heart rate during sleep: a method-comparison study with respiratory gas analysis

BMC Sports Sci Med Rehabil. 2019 Nov 4:11:27. doi: 10.1186/s13102-019-0140-x. eCollection 2019.

Affiliations

¹ 1Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan.
² 2Department of Rehabilitation Medicine, Fujita Health University Hospital, Toyoake, Japan.
³ 3NTT Device Innovation Center, NTT Basic Research Laboratories, NTT Corporation, Atsugi, Japan.

Abstract

Background: The recent development of wearable devices has enabled easy and continuous measurement of heart rate (HR). Exercise intensity can be calculated from HR with indices such as percent HR reserve (%HRR); however, this requires an accurate measurement of resting HR, which can be time-consuming. The use of HR during sleep may be a substitute that considers the calibration-less measurement of %HRR. This study examined the validity of %HRR on resting HR during sleep in comparison to percent oxygen consumption reserve (%VO₂R) as a gold standard. Additionally, a 24/7%HRR measurement using this method is demonstrated.

Methods: Twelve healthy adults aged 29 ± 5 years underwent treadmill testing using the Bruce protocol and a 6-min walk test (6MWT). The %VO₂R during each test was calculated according to a standard protocol. The %HRR during each exercise test was calculated either from resting HR in a sitting position (%HRR_sitting), when lying awake (%HRR_lying), or during sleep (%HRR_sleeping). Differences between %VO₂R and %HRR values were examined using Bland-Altman plots. A 180-day, 24/7%HRR measurement with three healthy adults was also conducted. The %HRR values during working days and holidays were compared.

Results: In the treadmill testing, the mean difference between %VO₂R and %HRR_sleeping was 1.7% (95% confidence interval [CI], - 0.2 to 3.6%). The %HRR_sitting and %HRR_lying values were 10.8% (95% CI, 8.8 to 12.7%) and 7.7% (95% CI, 5.4 to 9.9%), respectively. In the 6MWT, mean differences between %VO₂R and %HRR_sitting, %HRR_lying and %HRR_sleeping were 12.7% (95% CI, 10.0 to 15.5%), 7.0% (95% CI, 4.0 to 10.0%) and - 2.9% (95% CI, - 5.0% to - 0.7%), respectively. The 180-day, 24/7%HRR measurement presented significant differences in %HRR patterns between working days and holidays in all three participants.

Conclusions: The results suggest %HRR_sleeping is valid in comparison to %VO₂R. The results may encourage a calibration-less, 24/7 measurement model of exercise intensity using wearable devices.

Trial registration: UMIN000034967.Registered 21 November 2018 (retrospectively registered).

Keywords: 6-min walk test; Exercise intensity; Heart rate; Percent oxygen consumption reserve; Wearable devices.