Beyond Heart Rate: Heart Rate Variability
The technology now exists to extract a lot more information from our heart than simply how fast it beats. Tiina Hoffman, from Firstbeat, explains how we can turn heart rate variability data into insights about stress, recovery, and exercise.
Optimal performance at work, in sport, and in life can sometimes be quite a balancing act: staying resilient and coping with a multitude of life’s demands, while trying to follow good lifestyle guidelines – eat well, keep hydrated, exercise enough (but not too much…) find time to recuperate and sleep enough. This balancing act is not an easy equation, but it has opened way for a wide range of technological solutions, devices and apps to help us manage stress and to perform at the top of our game. The positive influence of a balanced lifestyle on health and performance is backed extensively by science. The literature shows, for example, that appropriate physical activity (Haskell;Blair ja Hill 2009) and good-quality sleep support recovery from day-to-day and long-term stresses (Porkka-Heiskanen;Zitting ja Wigren 2013), and contribute positively to overall well-being. (Firstbeat Technologies, Oy. 2014)
Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between consecutive heartbeats. 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. This article describes a method for analyzing heart rate variability to draw conclusions about important lifestyle factors. The method, developed by Firstbeat Technologies Oy, is based on advanced mathematical modelling, with empirical physiological and behavioral research in the background (Firstbeat Technologies, Oy. 2014). The principle is to utilize heart rate reactions and heart rate variability to evaluate stress reactions, recovery, sleep quality and physical activity in daily life. The method is considered a tool for professionals and can be used in corporate wellness, preventive occupational healthcare, lifestyle coaching, and in a broad range of sports settings.
The autonomic nervous system and HRV
The autonomic nervous system (ANS), consisting of the sympathetic and parasympathetic branches, work behind the scenes to regulate a wide range of physiological functions that we have relatively minimal conscious control over, but are necessary to maintain life and performance across a diverse set of activities and demands. 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 role of the ANS is particularly obvious with the heart. When the body is faced with stress, the ANS kicks in by activating stress hormone production and increasing the rate and force of contraction of the heart (cardiac output). On the contrary, for example after stress or exercise, parasympathetic stimulation decreases the heart rate to restore homeostasis. Measuring the heart at beat-by-beat accuracy provides us with a vast amount of information about the body. It is commonly accepted as a non-invasive marker of autonomic nervous system activity and serves as a powerful tool for observing the activity levels and interplay between the sympathetic and parasympathetic systems. A variety of physiological phenomena affect the level of HRV. For example; inhalation and exhalation (a symptom known as respiratory sinus arrhythmia: heart rate increases and HRV decreases during inspiration, whereas heart rate decreases and HRV increases during expiration). hormonal reactions, metabolic processes, exercise, movement, cognitive processes, stress and recovery (Task Force of the European Society of Cardiology the North American Society of Pacing Electrophysiology 1996).
In a normal situation, HRV should naturally increase during relaxing activities, especially during sleep, when parasympathetic (vagal) activation increases. On the other hand, HRV decreases during stress, when sympathetic activity helps the body to keep up with demand. Thus, HRV is typically higher when the heart is beating slowly, and lower when the heart starts to beat faster. HRV changes naturally from day to day. based on the level of activity and amount of, for example, work-related stress, but if a person is chronically stressed or overloaded (physically or mentally), the natural interplay between the two systems can be disrupted, and the body can stay constantly in a sympathetically dominate fight state, with a low HRV.
In the context of athletes, long-term overload due to an imbalance between training (too much and/or too intensively) and other life stressors, versus sufficient recovery, is known as overtraining. Studies suggest that overtraining is often characterized by increased activation of the cardiorespiratory and sympathetic nervous systems and a lowered HRV. In addition to overload and external stress, internal stress factors, such as poor nutrition, alcohol use and various illnesses can reduce HRV. Genetic factors explain about 30 per cent of the overall HRV level, but a higher HRV is generally considered to be an indicator of a healthy heart, and a higher HRV has also been found to be associated with reduced morbidity and mortality, psychological well-being, and quality of life (Geisler, ym. 2010). A person can increase their individual HRV level by improving their overall health and fitness.
Beyond heart rate variability; into lifestyle insights
The Firstbeat analysis method recognizes different bodily states from the measured heart rate variability data by converting the heartbeats, via a sequence of calculations, into reports that illustrate what daily events cause stress or promote recovery, how good the quality of sleep is and whether the days include exercise that provides positive health and fitness effects. The calculation process uses HRV data to estimate, for example, oxygen uptake, respiration and energy expenditure, and to determine a reliable individual baseline and physiological range for each person, before producing results and conclusions.
To solidify the connection between the HRV data and the person’s behaviors, a journal of key events is kept during the measurement, and these events are shown on the report. A stress state signifies dominance of the sympathetic nervous system and includes positive and negative stress reactions, whereas recovery means parasympathetic dominance. The aim is not to eliminate stress because it’s a natural part of life and helps us to perform. Instead, the focus is to strive for a balance between the different demands and make sure that the stressors (such as high workload, family and overall life demands, intensive exercise, heavy training load, travel and general busyness) are counterbalanced by sufficient recovery and sleep.
Designed as a tool for professionals, the method allows the personal trainer or wellness specialist to ‘see beneath the surface’ and provide evidence-based coaching to help the clients take charge of their own well-being and make lasting lifestyle and behavioral changes.
Professional interpretation and discussion between the coach and client typically focuses on topics such as stress management, sleep and recovery strategies, balanced nutrition, sensible drinking habits, a balanced training program, better fitness and better resilience overall, A Common discovery that people make is how much alcohol worsen their sleep quality, particularly when combined with other stressors, such as a heavy workload or intense exercise. A clear dose-response relationship has been found, with the negative effects on sleep building up after just one to two units.
Fitness enthusiasts are often surprised to find out how much a high-intensity workout, especially if done in the evenings affects the following night’s sleep. It’s not a message to stop exercising, but to be aware of how much hard exercise loads the body and to pay better attention to sufficient sleep and a balanced program that includes easy recovery workouts. To bring the method into a very practical level, Figures 1 and 2 show a couple of real-life examples of personal insights gained from the report.
Case – Senior Manager
This case looks at a senior manager working in a high-profile banking job in London. The lifestyle measurements were Conducted by Optima-Life as part of their “Perform @ Your Peak Program”, and Simon Shepard, CEO of OptimaLife, has provided the insights for this case. The first assessment establishes a baseline and looks at “Energy and Performance and the second assessment is a follow-up. The workshops and coaching that form part of the program, look at a number of factors that influence personal resilience. Diet, exercise and sleep are the obvious ones, but also relationships, value alignment, focus and positive mindset, all of these are factors that can lead to changes in one’s ability to recover, perform and cope with the load of life.
Measurement 1 – As seen in graph 1, above, very little recovery was seen in the manager’s results over the 3-day measurement, and there were a lot of stress reactions during sleep time. This left her resources depleted. The client acknowledged having a very busy life, often neglecting to take care of herself or to allow time for sufficient rest or recuperative activity. Lunch was often taken on the run, hydration was ignored and there was little formality seen in trying to ‘switch off’ from work at the end of the day. The data was used to show her how her behaviors were affecting her physiology and this proved to be a motivational catalyst in creating a shift in mindset. The process helped give her permission to look after herself, take positive actions in critical areas, and ultimately to re-energize her life.
Measurement 2 – The amount and quality of recovery during sleep had improved significantly and the consumed resources were now being replenished (the graph is climbing) during sleep. The Client had started to find more time for recuperative exercise, was taking a greater interest in what and when she was eating and how she was hydrating. She felt more energized, more productive and more purposeful both at work and at home; see graph 2, above.
In a nutshell
Heart rate variability provides us with a non-invasive window to autonomic nervous system activity, health and fitness. The method described here 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 people make meaningful lifestyle and behavioral changes.
Firstbeat Technologies, Ltd. 2014. “Stress and Recovery Analysis Based on 24-hr Heart Rate Variability.”
Geisler, Fay C.M., Nadja Vennewald, Thomas Kubiak, and Hannelore Weber. 2010. “The impact of heart rate variability on subjective well-being is mediated by emotion regulation.”
Haskell, William L., Steven N. Blair, and James O. Hill. 2009. “Physical activity: health outcomes and importance for public health policy.” Preventive Medicine 49 (4): 280-282. Accessed 9 25, 2017.
Porkka-Heiskanen, Tarja, Kirsi-Marja Zitting, and Henna-Kaisa Wigren. 2013. “Sleep, its regulation and possible mechanisms of sleep disturbances.” Acta Physiologica 208 (4): 311-328. Accessed 9 25, 2017.
Task Force of the European Society of Cardiology the North American Society of Pacing Electrophysiology. 1996. “Heart rate variability: standards of measurement, physiological interpretation and clinical use.”
This article originally appeared in Functional Sports Nutrition magazine, July/August 2016