IMPORTANT: this post is outdated. HRV4Training offers now many more features and a better user experience, please refer to HRV4Training.com for the latest updates. Thanks.


HRV4Training is an app that helps you optimize your goals and prevent overtraining by measuring your Heart Rate and Heart Rate Variability (HRV). I built this app while trying to understand better how I was recovering from my running trainings, since HRV is a proxy to parasympathetic activity and therefore physiological stress (read more here). HRV4Training does not require a heart rate monitor, since it can accurately assess your HRV using the phone's camera.

This post serves as a quick start guide for the app, while more details on HRV features and HRV analysis for fitness can be found in previous posts.

Heart Rate Variability Logger is an app I developed to record, plot and export time and frequency domain Heart Rate Variability (HRV) features. The app is available for iPhone and Android, however features on Android are limited. This post is a sort of user guide where I cover in more detail the different features and some implementation choices.


App features:

• Extracts, plots, stores and exports heart rate, rr-intervals, time and frequency domain heart rate variability features (AVNN, SDNN, rMSSD, pNN50, LF, HF, LF/HF) 
  
• Configurable experience sampling for events annotation 
  
• Comparison between up to 3 recordings lets you get a better understanding of autonomic regulation and sympathetic/parasympathetic activity under different contexts in a glance 
  
• Step counter or accelerometer derived motion intensity for user context and activity tracking (step counter only for iPhones 5S) 
  
• Location tracking (lets you select between either GSM/WiFi to save battery power or GPS for high accuracy)
• Lets you filter data based on custom thresholds
• Shows heart rate in the app badge
• Configurable time window for features computation (choose between 30 seconds, 1, 2 or 5 minutes) 
  
• RR-intervals correction can be enabled to prevent ectopic beats or artifacts from affecting HRV features 
  
• Data export using iTunes or Dropbox 
  
• Tested for recordings longer than 24 hours 
  

I tried to cover also most of the questions that I got by email in the last few months. Please comment or email me if you have other comments or requests for future versions. More specifically, the post covers:

1. Introduction on HRV and applications
2. Hardware requirements
3. Quick start guide
4. Data acquisition and signal processing pipeline
5. RR-intervals correction
6. Features extraction
7. Data export and format