One of the newer ways we are starting to assess someones preparedness to train is by using Heart Rate Variability (HRV). There are a lot of companies such as Polar, HexoSkin and Omegawave that are starting to measure HRV, using readily downloadable apps and heart rate monitors.
Heart rate (HR) has been used for a long time to measure the amount of effort during a training session. Using both of these measurements, HR and HRV, should give us more information about how hard we should be training as well as how hard we're working in a given session.
So what's the difference between these two? Let's define what HR and HRV are:
Heart rate is the speed of the heartbeat measured by the number of heartbeats per unit of time. It is usually measured in beats per minute (BPM).
Heart rate variability is the beat to beat alterations in heart rate (The MacArthur Foundation, University of San Francisco).
To try and simplify that, HR is the total beats per minute. HRV is the time between each beat.
HR will vary with exertion. This is to deliver more oxygen to the working tissues for energy production. At rest (known as resting heart rate) the average adult's heart beats somewhere between 60 - 100 BPM (Medical news today). Resting heart rate can be used as a guide to fitness and improvement in fitness in healthy adults. This is because, the "fitter" you are the stronger and more efficient your heart is at pumping blood through the body. This link is to a table that can be used to describe relative fitness in varying age populations. There are some medical conditions associated with variations in heart rate such as TACHYCARDIA and more information on some of these can be found here.
Traditionally HRV has been measured in clinical settings using electrocardiograms (ECG). It is now being used as a new method for assessing the effects of stress in the body. It is measured as the time gap between your heart beats that varies as you breathe in and out (ithlete). The less stressed your system the greater the variation between beats, the more stress the less variation in time between beats. This gives coaches the ability to see how well recovered and prepared to train their athletes are. Thus giving them a guide as to how much training load should be placed on that athlete. This link has a nice explanation on HRV with some good graphics.
If you ever have any doubt as to the wellness of your clients you should refer them to a medical professional especially when it has anything to do with the heart.