Endurance athletes love to train and push themselves. It can be tempting to keep increasing volume and miss a few rest days to get that weekly volume up. It can be challenging to know when to push and when to take an easy training day or rest day. To make these decisions athletes need a full toolbox of resources. These resources may include a coach, a periodized training plan, and metrics such as resting heart rate, subjective metrics such as fatigue, muscle soreness and overall feeling, as well as heart rate variability.
What is HRV?
Heart rate variability (HRV) represents the variation in time intervals between heart beats. The autonomic nervous system regulates cardiac responses to physical and psychological stimuli through the interaction of the sympathetic and parasympathetic nervous systems (Fatisson, Oswald, & Lalonde, 2016). A dominant sympathetic nervous system is reflected by a relatively constant time interval between heart beats. On the flip side, a dominant parasympathetic nervous system is reflected by more variable time intervals between heart beats.
Why should you care about HRV?
A reduced variability between heart beats can negatively impact the immune system, self-regulation, and psychosocial abilities (Fatisson et al., 2016). The time interval varies as the parasympathetic nervous system becomes more dominant, and this greater variability between heart beats means the heart can adequately react to stressors (Fatisson et al., 2016).
Athletes can use daily measures of HRV as one useful tool to help guide their training decisions. For example, if HRV is significantly lower and it is matched with poor subjective metrics such as fatigue, high muscle soreness, and poor training the day before – the athlete should adjust their planned training that day.
This athlete’s metrics were flagged due to them ranking fatigue as high; mood as worse than normal; soreness as high; and motivation as below average.
How to improve your heart rate variability
Sleep quantity and quality
A reduction in sleep quantity and/or quality negatively impacts your ability to recover. This impacts the autonomic nervous system with dominance of the sympathetic nervous system. People with disturbed sleep such as people with obstructive sleep apnea have reduced parasympathetic control of heart rate and reduced HRV (Stein, 2012).
Marco Altini’s app, HRV 4 Training, has metrics included with the daily measures of HRV where you rank your sleep quality among other metrics such as muscle soreness, fatigue and training history. This allows you as an individual to detect patterns between your own sleep quality and HRV measures.
Limit alcohol intake
This has been of personal interest to me in the last year. I have experimented with different amounts of alcohol and morning supine (lying down) measures of HRV using the app, HRV 4 Training. The app asks you to rank your alcohol intake for the day prior as none, a little, or too much. As you can see in the graphic below, when I rank my alcohol intake as too much, my HRV is reduced compared to when I rank my intake as none or a little.
For myself, alcohol intake had a greater effect on HRV than the amount of training I was doing. This experiment provided to be useful so I can keep my alcohol intake to none or a little to aid in my overall health, performance, and recovery.
When the athlete ranked their alcohol intake as ‘too much’, their HRV was lower indicating increased physiological stress.
Take planned rest days
Whether you love them or hate them, rest days serve a useful and necessary purpose. To improve your performances and recover properly, you will need to take planned rest days as part your training regimen. A research study measured HRV in well-trained female cyclists as they raced the 21-day Tour de France circuit. They found that HRV measures decreased during the event but returned to baseline within one week after the event (Barrero et al, 2019).
HRV can not be the only metric you use to make training decisions. However, it is a useful tool to complement other metrics. With improved technology and the ability to use your phone to take accurate HRV measures, I encourage athletes to include HRV in their daily practice.
Barrero, A., Schnell, F., Carrault, G., Kervio, G., Matelot, D., Carré, F., & Le Douairon Lahaye, S. (2019). Daily fatigue-recovery balance monitoring with heart rate variability in well-trained female cyclists on the Tour de France circuit. PLoS One, 14(3), e0213472.
Fatisson, J., Oswald, V., & Lalonde, F. (2016). Influence diagram of physiological and environmental factors affecting heart rate variability: an extended literature overview. Heart International, 11(1), heartint-5000232.
Stein, P. K., & Pu, Y. (2012). Heart rate variability, sleep and sleep disorders. Sleep medicine reviews, 16(1), 47-66.