Firstbeat Recovery Index

Over the past year we’ve been working with the Firstbeat system to track training and assess recovery. We started this project in order to work with Kris Freeman and Tad Elliott. Kris is a type-1 diabetic, and managing his training and racing stresses coupled with the complexity of his endocrine response has made it challenging to keep him on track once travel and racing begin. Tad has been returning from a serious overtraining situation, complicated by a mono infection. Along the way we’ve learned a lot about both of these guys and the way they respond to training. We’ve also learned about ourselves, and about the capabilities and promise of the Firstbeat system for other people like us – working folks who don’t have the luxury of a full-immersion approach to athletic goals. We have a lot of information to pass along, but the first step is to discuss the Firstbeat recovery index.

In a previous article I discussed the EPOC calculation that Firstbeat provides as a tool to quantify the disruption to homeostasis that a given training session incurs. Accurate assessment of training impact is a critical tool in training management, but as many people have observed, the real holy grail in training management is recovery assessment.

Jason Cork's arm. Some people take supercompensation really seriously.

Jason Cork’s arm. Some people take supercompensation really seriously.

Put simply, training works through a process of adaptation. We subject our system to a stress – a disruption (think EPOC). In response the body compensates by rebuilding to accommodate an increased stress load. That rebuilding process, and one hundred percent of the gains made in training, come during recovery. The process is well described by the theory of supercompensation, which is easy to research online if you aren’t totally familiar with it already.

When we plan training we focus almost exclusively on stressors; on the training itself. Training is planned quantitative and qualitatively, with elaborate schemes to manage periodization and load cycling. But most often the recovery side of the equation is left out of the calculus with the exception of an occasional recovery day.

The problems begin when training recovery demands have to compete for resources with additional stressors. With young athletes it all feels easy because time and energy tend to run a surplus. You train more and you go faster. But as training volume increases with age, so do other stressors (hours of homework, job commitments, relationships, etc), and almost every athlete runs into a time and energy deficit at some point by early adulthood. The critical thing is to understand that we have one supply of vital energy with which to fuel all of our needs. The same energy we need for training and recovery also has to power us through school, homework, jobs, and social obligations. We normally think of training stressors as being physical, but emotional stress drains the same pool of common energy. At almost every level, success depends on the successful balance of life and athletics, and the successful funding of recovery demands.

It’s easy to see the value of an accurate recovery metric – a method of quantifying the state of recovery and readiness for more training. A means of detecting accumulating fatigue and a circuit-breaker to prevent a chronic state of over-training. Over time many recovery tests have been proposed. I have personally taken lots of resting heart rates, from a simple pulse count, to various orthostatic tests, to a bunch of knee bends with follow-up heart rate measurements. These efforts have generally been for naught; they have failed to even provide an accurate picture of the current state of recovery, let alone any predictive power to help guide training decisions. They have likewise failed to impress in a more scientific setting. There isn’t a lot of support for resting heart rate tests in scientific literature.

This is where heart rate variability provides some interesting new insight. Let’s revisit my description of the factors influencing HRV from my first article on Firstbeat.

About Heart Rate Variability

Heart function is governed by the autonomic nervous system; along with all other “automatic” systems in the body. But the ANS has different regulatory systems, and heart function is controlled by a combination of two of them. The parasympathetic nervous system governs body functions at rest, while the sympathetic nervous system governs the “fight or flight” response to stress. These two systems work in complementary opposition to maintain a state of balance in the physical systems that they govern. The parasympathetic influence lowers the heart rate and increases the variability between beats, while the sympathetic influence raises the heart rate and increases the regularity of the inter-beat interval. So a measurement of heart rate variability amounts to a fairly direct measurement of nervous system function.

This snap-shot of nervous system function amounts to a quantified assessment of the influence of stress on the ANS. The presence of sympathetic nervous system influence on heart rate (resulting in elevation of the HR, and in decreased variability) indicates a stress-response. Now we’re getting somewhere.

HRV assessment has captured the popular imagination – at least among the early-adopter crowd. There are quite a few very inexpensive packages that allow you to assess heart rate variability. You can even get a free iPhone app that uses the flash-bulb and camera to make an optical measurement of heart rate, and assign a stress score based on HRV. Some of these packages are aimed at athletes, while many are aimed at the stress-management market in the general population. But they measure the same thing.

There are two ways that Firstbeat provides better information than an iPhone app. One is simply the science. There is a great deal of scientific and medical information on HRV, and the people who started Firstbeat conducted a lot of the seminal research in the field. As a layperson, when I think of HRV it’s easy for me to think in terms of the “R-R interval” – the time between those familiar spikes in the ECG line known as the R-wave. But the actual assessment of variability has to be calculated and quantified, and there are various ways of doing this. Even a quick browse through the Wikipedia entry on HRV quickly gets over my head, but it’s important to understand that the different frequency variations correlate to different health and recovery concerns.

Recovery report showing strong stress response during sleep.

Recovery report showing strong stress response during sleep.

According to Jim Galanes, the recovery index draws heavily on base heart rate and on the RMSSD calculation. Firstbeat provides raw beat-by-beat data, as well as beat by beat calculations of a handful of different variability assessments. Jim has worked with the raw data extensively, and finds that the Firstbeat Index is a very robust indicator of recovery for the purposes of training management.

The other Firstbeat advantage is the duration of the sample. Most of these app-based tools measure a two to five minute sample of your heart rate. The more sophisticated packages stress the importance of being regular in your sampling time and environment, and one even gives you a visual guide to time your breathing (because variability increases on exhalation and decreases on inhalation). While Firstbeat does offer the option of a quick five-minute recovery test, the real value that we see comes from the overnight measurement.

The Firstbeat recovery index is based on a four-hour sample of sleeping heart rate. It’s easy to understand why a four-hour sample is going to provide more reliable information than a five minute sample. The sheer quantity of data and the length of the measurement ensure that the natural ups and downs get averaged into a more accurate assessment of your recovery state. The measurement happens when you’re asleep, while active recovery is actually happening. It’s a totally background test – not something you can learn or manipulate by changing your breathing or your mental state.

There are some pretty well designed and credible training management programs out there these days. When it comes to managing training load from the input side (quantification of training stresses, and assessment of training performance) Firstbeat offers a viable option, and hardly the most user-friendly interface. Firstbeat makes no attempt to guide your training or provide any “coaching” input. Firstbeat is a tool designed for professionals, to augment a good understanding of training theory and physiology. EPOC is a great tool for quantifying training disruption, but there are other options out there that have good tools for quantifying training stress, and probably a more intuitive user interface. The raw power of Firstbeat really comes into focus when we add sleep measurements and the recovery index to the picture. Now we’re measuring on the output side of the equation, and we’ve actually got something to balance!

Recovery report showing high levels of relaxation and good sleep quality.

Recovery report showing high levels of relaxation and good sleep quality.

I should clarify this because it’s worth arguing that other training management packages provide good markers of stress or fatigue. Most of these assessments are based on workloads during training; performance testing. What Firstbeat offers is a direct measurement of systemic stress during recovery time. HRV measurement is by far most effective at rest, because this is where the influence of parasympathetic and sympathetic nervous system influence are in direct opposition and balance. When you’re active your heart rate is elevated, which means that, by definition, you sympathetic nervous system is dominant and HRV is suppressed. There is still room for HRV assessment of provide additional feedback on a training session, but it’s during recovery that the balance becomes sensitive. At rest the influences of stress and relaxation compete on equal footing, while during exercise the stress response of elevated heart rates will mask the balance. It’s like weighing two different marbles on a balance scale, and then dropping a 10kg weight on one side. Now which marble is heavier? In order to use HRV as an accurate tool to assess recovery, the measurement must be during recovery.

Please read the last two paragraphs again. I’m trying to explain why Firstbeat is a unique tool because it actually measures your recovery response during recovery. It’s not coming up with a predicted recovery value based on the training that you’ve done. It’s showing you precisely how your body is responding to all the stresses in your life. This is important.

All of this is well and good for dedicated elite athletes, but is there value for grown-ups? People with lives, jobs, and obligations outside of honing their physiology to the finest point possible? The answer is an unqualified yes, but that doesn’t mean that it’s going to make life easy for you. Amateur athletes with full time jobs and families are in a tough spot, balancing far more demands than most elite athletes need to be concerned with. When I do a daytime measurement on myself during a working day I see fifteen or sixteen hours of non-stop stress markers. I see sleep quality decline and recovery index scores take a dive without even adding any training to the mix. In the spring and early summer, when we’ve got lots of down-time and I can immerse myself in fitness goals and relaxation, fitness comes up quickly, and I start to believe I can get fast. It doesn’t take many workday measurements to realize how impossible it is to make it through the Fall grinding season with fitness intact, and anything other than a big backlog of fatigue to shrug off after the holidays.

Like all good information, Firstbeat can provide context and seed understanding. It can give you the feedback to modify your lifestyle within the constraints that your life imposes. For many of us, the picture isn’t terribly encouraging. If you prefer not to face the limitations that real life imposes, then I recommend spending your money on some new fast skis and ignoring all of this. But if you’re serious about finding better balance in your life and making better use of your training time, then you should seriously consider the tools available.

And you should still buy those skis.

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