HRi

# HRi: Heart Rate Info app 1) Lets you compare hear-rate as measured by your watch's optical sensor vs an Ant chest strap. 2) Show traces of heart rate and cadence over about last 2 minutes. 3) Investigate HRV (heart rate variability) by looking at RR intervals. The app shows a measure of HRV (Heart Rate Variability) as ln of rmssd of RR intervals (root-mean-square, of successive differences). To compare optical and chest strap HR measurement, make sure your watch is NOT paired to an Ant chest strap. So the watch reports HR from its optical sensor. Showing both HR measurements on the watch is much more convenient than wearing 2 watches. It helped me gain confidence in good fit, and accuracy of the watches optical HR at steady running /cycling pace. The shows a trace over about the last 2 minutes, so you can see impact of smoothing / lag when sprint or take it easy. You can record your activity to look at HR measurement later and in more detail Garmin Connect. Cadence is shown because some mailthreads suggest that some devices that do optical HR measurement at wrist can suffer 'cadence lock' when running. This hasn't been a problem for me, but I wanted to make it obvious in case watch fit is a problem. The links below and internet search can tell you about HRV. How + when to measure and how people interpret changes in their HRV from a personal baseline tracked over time. - Papers I looked at recommend measuring HRV at rest first thing in the morning (with consistent body position). - The Ant chest strap heart beat RR measurements the HRi app uses are about 1Hz, which is adequate for my resting HR. They would NOT be frequent enough at higher heart-rates when exercising. # Disclaimer Basically the normal disclaimer. Its great that consumer devices like Garmin watches gives such easy access to interesting biometric and sports performance information, and that there is an open platform to record, chart and analyse. - HR and cadence are as reported by watch and Ant sensors. - The HRV measure (lnrmssd) is not intended to be taken as accurate to any standard. HRi filtering of RR data and processing is very basic. HRi drops obviously out of range RR values. For example analysis has NOT been done to detect and remove entropic beats or other artifacts; there has been NO calibration or comparison vs reference equipment (eg ECG). # Links - HRV Heart Rate Variability: https://en.wikipedia.org/wiki/Heart_rate_variability - RR-interval: Interval between successive R points (peak of QRS complex of ECG wave): https://en.wikipedia.org/wiki/Heart_rate#Electronic_measurement # Screens ## Intro screen Shown on startup only. Lists the screens. ## HR Screen You can use this screen to see how the watch's optical HR measurement compares with an A - HR from Ant HR strap, or 0 if not available: Current value and trace (in red) - HR reported by watch: Current value and trace (in green, with 'w' label) - Cadence reported by watch (if available, in yellow) ## HRV Screen - HR from Ant HR strap: Current value and trace (in red) - A measure of HRV (Heart Rate Variability): ln(rmssd of RR intervals) - Traces of HR from watch, Ant chest strap, cadence and lnrmssd. # Controls (based on my Garmin 235) - up/down buttons swap screens - 'run' button start/stop recording. A red square in top-right of screen indicates you are recording. - Back button gives menu asking to confirm exiting the app. # FIT file recording contributions - 'HR' Ant HR (bpm) - HR from Ant HR strap rather than reported by watch in the 'heart_rate' field. - 'RR' (ms) - Heart rate RR interval as reported by Ant HR chest strap. - 'hbc' Heart Beat Count - As reported by Ant HR chest strap (needed so you can analyse RR data). - 'lnrmssd' HRV ln(rmssd): A measure of HRV (Heart Rate Variability). ln of root-mean-square of successive differences between RR intervals. Calculated by app based on rr + hbc readings from Ant HR chest strap.

# HRV Dev Screen (disabled by default) - HR from Ant HR strap: Current value and trace (in red) - rmssd of RR intervals - ln(rmssd of RR intervals) - Info on number of good/bad RR samples when calculating rmssd of RRs. - Status of Ant HR connectivity - Traces of: HR from watch and Ant chest strap; RR interval; lnrmssd. # RR Dev Screen (disabled off by default) - HR from Ant HR strap: Current value and trace (in red) - rmssd of RR intervals - ln(rmssd of RR intervals) - RR interval and HBC (heart beat count) - Status of Ant HR connectivity - Histogram of RR - Traces of: HR from watch and Ant chest strap; RR interval. # TODO - Pair and remember Ant HR chest strap - Select recording type: Run, Bike, HRV - Enter posture for HRV recording. - Add time, timer and distance information - esp when recording an activity - Daily HRV recording and trending.