HRV (Heart Rate Variability)
WHAT IS HRV?
Physical movements remain the key to an athlete’s well-being both on and off the field. All physical movements, in one way or the other, have an effect on the heart. As technology develops, enabling our measuring abilities, researchers were quick to establish a reliable measure relating to the heart and the intricacies of the heartbeat.
Heart Rate Variability (HRV) is the physiological phenomenon of variation in the time interval between consecutive heartbeats. The HRV is simply the time difference between each successive heartbeat. The time between each heartbeat is inconsistent, it varies with every beat hence the term heart rate ‘variability’. HRV’s popularity has increased over time as continued research into the metric has helped identify its association with athletic performance and recovery. Propagating it further are now many HRV tracking apps available for simple daily monitoring using a smartphone.
The level of HRV varies a lot between individuals, but in general terms, high HRV is viewed as a marker of good fitness and health, whereas low HRV is associated with a range of negative health outcomes and stress. Variability in the heart rate provides critical information about the function of the autonomic nervous system (ANS) and is also the most reliable measurement of ANS function. The autonomic nervous system (ANS) consists of the sympathetic and parasympathetic branches. The sympathetic branch is regarded as the “fight or flight” system, getting us ready to act, react and perform, while the parasympathetic side is often characterized as the “rest and digest” system. Both systems typically function simultaneously, but in opposition to each other, either activating or inhibiting specific physiological responses.
The sympathetic branch (SNS) stimulates the body for the stressors experienced during a performance, and the parasympathetic side (PSNS) is vital for recovery and regeneration. It is believed that an “imbalance” between the SNS and PSNS can lead to reductions in athletic performance, and in more extreme cases, lead to overtraining. The working of the SNS and the PSNS determines the performance and recovery phases of an athlete using the HRV. The two in some ways go hand in hand according to various researches regarding HRV. The HRV analysis is a valuable asset as far as recovery of an athlete goes. A baseline can be set depending upon the various HRV readings, measured over a course of time for recovery from strenuous training regimes.
HRV IN RELATION TO RECOVERY AND TRAINING?
One such study observed a reduction in HRV 24-hours post-workout after a high-intensity strength training session. HRV and weightlifting performance returned to baseline (i.e. pre-workout values) after 72-hours of recovery, indicating a certain relationship between HRV and recovery. It was reported that immediately after a heavy workout in pre-tournament camps, the HRV of athletes took a significant drop. They were, however back to baseline and in some cases even rose to higher values during the tournament when the levels of training were slightly lowered. Another such study which monitored athletes over a long period of time (multiple months) found that HRV increased during an intense training period and stagnated and lowered during an overload training phase. However, after a 2-week recovery period, it rebounded and even led to an increase in HRV. Indicating that intense training regimes may end up improving HRV.
The concept of HRV-guided training versus pre-planned training is often used and studied in sustaining and improving performance levels. HRV-guided training refers to structuring each training session based on the athlete’s HRV reading. Meaning that if the athlete’s HRV is normal or higher than normal, and then they will be prescribed with a relatively intense training session. Similarly, when the athlete’s HRV is below normal, then they are arranged an easier, lower-intensity session. Pre-planned training simply refers to a programme that has already been designed and does not cater for daily changes in HRV. Various studies have shown that HRV-guided training may be more beneficial for improving aerobic performance compared to pre-planned training. Also suggesting that athletes who have a higher HRV score may be more sensitive to performance gains than those with a lower HRV score.
Polar Team Pro is one of the many technology providers who are deeply associated with HRV and its usage on a professional level. Their client list includes some of the heavyweights of the modern sporting world. Bayern Munich, Wolfsburg, Liverpool happen to be some of their footballing clients. They’re also associated with Golden State Warriors and Miami Heat in the NBA and the Surrey County Cricket Club.
“Polar Team Pro has enabled us to capture data quickly and easily by having one sensor that houses heart rate and GPS rather than a separate GPS sensor. The feedback on heart rate coupled with speed and distance means we have a clear picture of player fitness. Using this alongside training load and recovery we can ensure players are working at the right level to improve and maintain their fitness during the season.” David Sykes, Head of Physical Performance, Kilmarnock FC (Scottish Premier League).
HRV AS IT STANDS AND FUTURE POSSIBILITIES:
The method of measuring and identification in HRV is based on forming a physiological model of an individual by utilizing information provided by real-life heartbeat data. This data can be used to draw conclusions about stress, recovery and exercise, and about how the body is coping overall. In a wider professional context, this provides a powerful preventative tool for lifestyle and wellness coaching to help athletes and their coaches make better training related decisions and certain behavioral changes.
As technology advances, HRV measurements are only going to get accurate and more reliable. Companies and their products will only improve, aiding the reliability of the HRV as a measuring tool. HRV has been a major boon in readings pertaining to stresses, however, its specificity still remains a question. Whether the stress is physical, work-related, or other life issues, that aspect is still not completely answered by HRV yet and may require further developments to make that happen. Current researches have suggested that HRV is a reliable measure of the ANS function in adults. The situation in kids though is quite different. There appear to have been conflicting evidence with the research on children, some suggesting it might be reliable while others suggesting it might not be. Hence future research on HRV with regards to the different age groups is important.
HRV, for the highly technical and insightful metric it represents, is doing extremely well. It might not be easy to understand the intricacies and it’s working in one go but that doesn’t change the fact that it remains a highly informative metric system. The room for improvement is there and with the technological advancements and increase in researches towards HRV, this can be achieved.