What is HRV and how I use it

With the holidays over, and the new year upon us, I thought this would be the perfect time to review my 2019 season, and explain how my coach Inaki de la Parra and I used HRV4Training to track how multiple stressors potentially affected performance.

Any sort of training, especially hard workout sessions or long endurance bouts of exercise, creates stress in the body. One single workout will not necessarily help you improve performance, but the constant exposure to stress and rest will create adaptations in our body that will increase the ability to maximize oxygen utilization, accelerate the recovery process, and will therefore result in performance gains. Stress is good! When we are stressed, our parasympathetic nervous system shuts down, and our sympathetic nervous system activates. This is known as the "Fight or flight" response. Our body gets ready for action, increasing our heart rate, sending blood to our bigger muscles, and taking it away from less necessary organs such as the stomach, and extremities. Had it not been for this, humans would have never survived during the stone age.

However, the problem is that we no longer need to run away from lions, or hunt for our food. Instead, we are constantly bombarded by little stressors such as email notifications, quick turnaround projects, Instagram likes, etc. So, how does this relate to training and HRV? Well, it relates a lot! HRV measures our Heart Rate Variability, which is an indicator of how activated or not our sympathetic nervous system is. If we are constantly stressing our body without enough rest, then we are not producing the necessary adaptations to improve performance, and we are actually increasing our chances of burnout, injury, or getting sick. Picture a day in the life of most of us. We wake up around 5:00 AM, rush to get our first training session done (stress), quickly shower and grab breakfast before rushing out the door to drive to work or catch the train that is about to leave (stress). After a long day at work (stress), we cram a second training session (stress) before dinner. If we had a long day, we will probably be wired from everything that happened that day, and go to bed at around 10:30 PM (rest). Notice that the number of stressors during the day outnumber the number of times we are at rest. However, the intensity of certain stressors can potentially negatively impact our HRV. An accident, for example, can have a greater impact than the daily routine. This is why keeping track of our HRV can help us adapt our training to our lifestyle, detect early signs of sickness or maladaptations, and maximize our training.

Keeping this in mind, take a look above at my HRV trends during 2019. My season started strong, with consistent and improving trends, but a bicycle accident and a broken wrist created a big dip in my trends. This makes sense as the stressors of trauma and the psychological stress of recovery can take a toll in your body. While I didn't really stop training, I was limited to indoor biking and some running. Soon after recovery, however, trends rapidly improved and remained stable for most of the first half of the season. This was a good indicator that my body was adapting well to training loads, and I was managing stress appropriately. It is worth noting that changes in environment can also create stressors that can worsen your HRV, such as altitude training. A good example is the training camp I went to in June at Boulder. Changes in altitude and increase training load created a small dip in my HRV (you can read more about it here).

When looking at my race performances, and comparing them against my HRV, my worst performance was probably during Ironman 70.3 Santa Cruz (September 9th). While Ironman 70.3 Muskoka (July 7th) was soon after the training camp, the rapid, but acute training loads had a better effect on me than long, sustained stressors from work prior to 70.3 Santa Cruz. Not surprising. This was probably due to lack of sleep, and increased fatigue towards the end of the season. Changes in HRV also happened because of sickness and holidays, though I wasn't as concerned during this time since this happened after IM Arizona (November 24th).

So why do I do all of this? First, because I want to make sure I maximize my training and avoid burnout, but also because I want to improve my aerobic efficiency. Meaning, I want to maximize oxygen utilization, improve carbohydrate utilization, and avoid cardiac decoupling.

A lower heart rate at a faster pace over a prolonged period of time is an indicator that your body is becoming more efficient in utilizing oxygen. For endurance athletes, this is key since we want to make sure we can push at a given speed or pace for many hours. However, increased training loads, even at low intensity, can be detrimental if not monitored appropriately. HRV4Training is a great resource to learn more about heart rate variability, and its uses go beyond endurance athletes.

I want to thank Marco Altini from HRV4Training for all the support during the 2019 season! I'm also excited to continue to be part of the HRV4Training team for the 2020 season, and all the races ahead. Happy new year!