About this app

It is generally assumed that heart rate is fairly constant, becoming gradually elevated during periods of exertion then reducing during rest.

The time period between the impulses that stimulate the heart to beat (known as R-R Interval) actually varies significantly for a constant average heart rate.

This variation known as Heart Rate Variability (HRV) can provide interesting information about the subject, such as:

- Indication of over-training (1) (2)
- Monitoring recovery from a competition or workout (3)
- Identifying when the athlete is able to undertake hard training (4)

Various parameters have been established to classify HRV, the most notable being SDSD,; RMSSD; SD1 and SD2

This app calculates and displays these parameters in pseudo real time (update every 5 seconds based on the most recent 60 heartbeats). Also displayed is a histogram of the most recent SD1 values

In order to maintain reasonable stability in the parameters it is necessary to remove ectopic beats from the data set. Ectopic beats are when there is a short R-R interval followed immediately by a long R-R interval, the average of the two being similar to the R-R intervals either side of the ectopic beat.



Notes
1. This app is for general interest only and SHOULD NOT be used for any clinical purpose.
2. CONSULT YOUR PHYSICIAN before undertaking any strenuous activity
3. This app requires a Polar Wearlink+ Transmitter With Bluetooth (Available from Amazon)
- NOTE If you have a Bluetooth Low Energy Chest-strap such as Polar H7 or Zephyr HxM check out the new app HRVxt
4. App has been tested on Samsung S3 and S4

References
1. Effect of overreaching on cognitive performance and related cardiac autonomic control. Dupuy et.al, Scand J Med Sci Sports 2012
2. Decrease in heart rate variability with over-training: assessment by the Poincare´ plot analysis. Mourot et.al, Clin Physiol Funct Imaging (2004) 24
3. Heart rate variability before and after cycle exercise in relation to different body positions. Barak et.al; Journal of Sports Science and Medicine (2010) 9.
4. Endurance training guided individually by daily heart rate variability measurements; Kiviniemi et.al; Eur J Appl Physiol

Andrew Flatt has an excellent blog on HRV training that can be found here: HTTP://hrvtraining.com/

The Pro version of this app, now available (search Heart Rate Variability - Pro) will save all the R-R intervals (in mS) to a file that can be imported into a spreadsheet or Kubios HRV analysis software. In addition, a separate file will be generated that records all the parameters displayed on the screen, with the line numbers in the R-R file that were used to generate those values.

New features

V3.00

- Added LF/HF live display
- Ectopic beat detection now more aggressive
- App saves 2 files after approximately 200 beats have been received, File 'year-month-day-time-r2r' contains 60 beats.

V3.01

- Minor bug fix for users who have experience a crash

App Permissions

Allows an application to write to external storage.
Allows access to the vibrator.
Allows using PowerManager WakeLocks to keep processor from sleeping or screen from dimming.
Allows applications to connect to paired bluetooth devices.
Allows applications to discover and pair bluetooth devices.
Allows an application to read from external storage.