What are we able to measure and how?

Starting point

Human life is characterized by dynamic processes and biological rhythms. When we are active during the day, we become stimulated and engaged, but also tired after a while. Long-term good health is characterized by a dynamic situation where we constantly switch between activity and relaxation/recovery. Therefore, it is difficult to find an objective measure that illustrates health and well-being at a certain timepoint. You also need to take into account the context and the time course.

Physical exercise promotes health. However, physical exercise can also be described as a form of activation or physical stress reaction that needs to be followed by rest and restoring processes to become beneficial. Intellectual challenges can similarly be stimulating and involve learning and positive development. But also in that case, regular mental rest and recovery are needed for long-term positive effects. When measuring physiological parameters, such as pulse and blood pressure, during activity and rest you get different results, but in both these situations the results can be part of a long-term healthy process.

Healthy activities in nature can thus entail both active and more restful conditions. We usually want to measure signs of recovery of nature, but also more demanding activities in nature, such as physical exercise and social interaction may in the long run be health promotive.

For many, life has become too demanding and hectic. We feel stressed and do not get enough recovery between laps. We may in that situation down prioritize many healthy activities such as physical exercise and spending time with friends. But spending time in natural environments can help us shift focus and relax. In addition, nature stimulates us to healthy activities. Of course, we want to be able to measure these effects objectively, but it is a great challenge to be able to do so under different conditions and varying outdoor activities.

Many factors affect at the same time

In real life, it is difficult to isolate the influence of a specific factor from everything else that happens at the same time. When we do experimental research, we try to keep all other factors constant, but at the same time it means a rather unnatural situation, which can only be maintained for a limited time.

When we spend time out in nature there are many things that affect; nature's characteristics, our previous experiences, weather and wind, equipment/clothing, day form, food intake, whether we are physically active or not, simultaneous social contexts, life events, current medications and diseases etc. Age and gender could also matter. All this means that it is difficult to refine the effects of the natural environment alone.

In research, you prefer to have some form of control group or control situation where the people are not exposed to the factor you want to study, but where everything else is the same. This is difficult to achieve in reality. Methodologically, it is therefore an advantage if you can make repeated measurements on the same person. One could, for example, measure in nature and in urban environment respectively, on the same individual.

Short- and long-term effects

We can measure rapid, transient reactions of staying in nature, such as emotions, well-being, heart rate, blood pressure and hormones. But we can also examine more long-term effects on health. In the latter case, epidemiological studies are often used. One then studies fairly large groups in the population, who to varying degrees stay in nature, and then follows them up after a long time to examine their risk of developing various diseases. A problem in these studies is that you have to take into account other factors that differ between the groups you study. One could imagine that "natural people" also live healthier in general, exercise more, eat better food, do not smoke, etc.

Effects of interventions

For evaluation of nature-based interventions and rehabilitation, the best option would be to perform a randomized study where the participants are randomized to a treatment or control group. In these cases, the effects on health are usually examined after one or a few months of treatment. Unfortunately, it is often difficult to get a really good control group and especially when it comes to interventions which are implemented during a long time period.

New methods

There has recently been a strong development of new user-friendly methods for estimating physiological effects of stress and recovery. There are e.g. many wrist watches to buy that measure both your heart rate and its variability, physical activity and sleep. You usually receive feedback directly via the mobile.

It is more difficult to make measurements in groups of people because the equipments that are marketed today are usually designed for only individual feedback of the results. If you want to compile data from several people at the same time, you must have access to basic data from the company. And you must also take into account the requirements for integrity and data management that apply. In these cases, it is usually good to collaborate with researchers in the field. There is equipment to buy for research use where it is possible to collect data from many people and easily move all the data to a computer for further processing.  

Below is a summary of various methods that can be used to measure health effects in connection with spending time in nature. They are largely based on the theories that underlie nature's health-promoting effects and most of them have been used with good results in previous research.

Psychological measurement methods

Below is an overview of various methods that can be used to measure psychological health effects in connection with a stay in nature. They are largely based on the theories that underlie nature's health-promoting effects and most have been used with good results in previous research.

Evaluation of emotional, affective state

POMS (Profile of Mood States), PANAS (Positive and Negative Affect Scale)

Both POMS and PANAS consist of questionnaires that contain lists of different emotional expressions. The person estimates the extent to which the feeling has occurred recently. The instruments have been used in sports medicine to detect overtraining, but also in environmental psychological research. The number of emotional expressions can vary in different versions of the instruments.

Reference POMS - McNair, D. M., Lorr, M., and Droppleman, L. F. (1971). Manual for the Profile of Mood States (POMS). San Diego: Educational and Industrial Testing Service. Reference PANAS - Watson, D., Clark, L. A., & Tellegen, A. (1988). Development and validation of brief measures of positive and negative affect: The PANAS scales. Journal of Personality and Social Psychology, 54 (6), 1063–1070.

ZIPERS (Zuckerman Inventory or Personal Reactions)

The questionnaire contains 12 statements that measure the individual's feelings and level of anxiety at a given time. It has been used in environmental psychological research. The results are usually divided into five factors; 1/ fear, 2/ positive affect, 3/ anger, 4/ attention - coping ability, and 5/ sadness - melancholy.

Reference - Zuckerman M, Development of a situation – specific trait-state test for the prediction and measurement of affective responses. J Consult Clin Psychol 1977 Aug; 45 (4): 513-23.

Measuring MOOD according to Sonntag-Öström et.al.

This is a simple questionnaire designed to work well in connection with outdoor stays. It is based on different emotions or moods in the same way as in POMS and ZIPERS, but focuses on emotions that you can expect to see effects on when being exposed to natural environments. It consists of 6 questions on a 10-point scale and with two endpoints for each question; tense - relaxed, tired - alert, sad - happy, irritated - harmonious, restless - calm, divided - clear-minded. Read more about the mood survey here.

Sonntag-Öström E, Nordin, M, Slunga Järvholm L, Lundell Y, Brännström R, Dolling A. 2011. Can the boreal forest be used for rehabilitation and recovery from stress-related exhaustion? A pilot study. Scandinavian Journal of Forest Research 26: 245-256. 

Stress-Energi

A questionnaire with 12 questions that measure mental state. It has mainly been used in working life to measure emotions related to stress and energy. It has not yet been used to any great extent in research to measure health effects of nature, but should be able to work well.

http://nile.lub.lu.se/arbarch/ah/2002/ah2002_12.pdf

Experience of recovery in nature

PRS (Perceived Restorativeness Scale)

A questionnaire developed by Terry Hartig and based on ART (Attention Restoration Theory). It usually consists of 16 statements that measure four important components of the nature experience; 1/ "to be away from everyday life", 2/ opportunities for fascination, 3/ experience of a cohesive unity, and 4 /compatibility, ie. the environment meets my needs.

Reference - Terry Hartig, Florian G. Kaiser & Peter A. Bowler, Further development of a measure of perceived environmental restorativeness. Arbetsrapport / Working Paper No. 5. Uppsala University May 1997.

ROS (Restoration Outcome Scale)

This questionnaire usually consists of six questions that establish different dimensions of a restorative experience in the environment; relaxation, restored ability to pay attention, thoughts clear, and experience of vitality and self-confidence. It has been used in research on the restorative effects of natural environments.

Reference - Korpela KM, Ylén M, Tyrväinen L, Silvennoinen H. Determinants of restorative experiences in everyday favorite places. Health & Place 2008; 14: 636-652.

Neuropsychological tests

These tests are usually performed by psychologists and measure cognitive functions, e.g. ability to pay attention and remember. When you are out in nature, you should preferably use tests that are easy to perform. Some well-known tests in research about natural environments are the "Necker cube", Digit Span Forward, Digit Span Backward, and SDMT (The Symbol Digit Modalities Test) which is a decoding test. These tests measure focused attention, concentration and memory. It is important that the tests are performed in a standardized way in collaboration with a psychologist and/or researcher.

Reference - Ottosson J. The importance of the outdoor environment for the elderly with a great need for care. Edition 155 of Stad & Land (Alnarp 1982).

Qualitative interviews

There are different qualitative methods to use. The inductive method, which is commonly used in interviews, use primarily the content of the interviews to create a theory or model. With the deductive method, you apply an existing theory in order to be able to draw conclusions. You should have taken a course in qualitative methodology and collaborate with researchers who have experience of interviews. It is common to use an interview guide with fairly open-ended questions and to be prepared to go on with follow-up questions to get more information. In order to be able to make an accurate processing and analysis of the interviews, they should be recorded.

Physiological factors

When we perform measurements of stress and recovery with different physiological methods, it is largely a matter of demonstrating the effects of the autonomic nervous system. This system is regulated via various centers higher up in the brain and is greatly affected by our surroundings and how we perceive our situation. There are also several feedback systems from the body and our organs that affect the setting.

The autonomic nervous system controls many of the body's systems and organs, such as the heart, respiration, digestion and genitals. It consists of two parts; the sympathetic and the parasympathetic nervous system.

• The sympathetic nervous system is activated when we are engaged and active, and especially if we experience stress, threats and danger. It then helps us to quickly adjust so that we can act vigorously physically. The sympathetic activation leads to the formation of stress hormones, e.g. epinephrine, norepinephrine and cortisol, which affect the body and energy metabolism. Pulse and blood pressure rise, blood circulation increases, we sweat and get an increased muscle tension, we wake up and become alert. Energy is mobilized through the release of sugar and fatty acids.
• The parasympathetic nervous system, on the other hand, is characterized by "peace and rest". It is activated e.g. after a good meal when we doze off and feel well. It benefits digestion, restoring processes and recovery. There are also anabolic hormones that are produced when we rest, such as growth hormone and sex hormones.
  Both systems are needed for our survival and health. We need to have a good balance between them. An acute stress reaction always needs to be accompanied by a period of recovery.

Heart rate

The heart rhythm and especially the heart rate variability reflects the activation of the autonomic nervous system. Variability refers to the variation of time between two consecutive heartbeats. The heart's rhythm should normally vary cyclically and it is affected by, among other things, breathing. A high degree of heart rate variability (HRV) is a sign of freshness and is more common in young people compared to older people. When the sympathetic system is activated, the heart rate increases and the variability decreases. This occurs both during physical activity/physical exercise, and in connection with mental stress. When the parasympathetic dominates, the heart rate drops and the variability increases. By measuring HRV, you can thus get a good measure of ​​the activity of the autonomic nervous system, which can be translated to whether you are stressed/activated or in a recovering state. Age, physical activity, illness and medication can affect the results.

You can use different methods to measure your heart rate. You can of course feel the pulse and count the number of beats per minute, but this is a rather uncertain method and gives only a rough idea of ​​the heart rate. The classic method is to attach electrodes to the chest and measure the electrical signals when the heart is activated, which is called ECG, electrocardiography. When you get exact ECG registrations, it also becomes possible to calculate HRV.

Today, many people use wrist watches to measure physical activity, stress and rest/recovery on themselves. In wrist watches, an optical method is used to measure the heart rate via the wrist pulse. With heart rate monitors around the chest or electrodes on the chest, an ECG is measured, which is considered a better and more accurate method. However, it has been shown that there is a fairly good agreement between ECG and optical measurement and both methods can be used for calculating HRV. The HRV results can then be translated into scores for e.g. stress and recovery. The activity watch usually also contains an accelerometer which means that you can simultaneously measure physical activity and the number of steps. There are also watches that calculate oxygen uptake, sleep time and sleep quality. There is also a ring on the market that is worn on the finger and that measures heart rate, respiration, sleep, body temperature and physical activity.

In summary, there are many different devices for measuring heart rate. Collected data also needs to be stored and processed in order to be able to compile and present results. This is usually done through an application in the user’s mobile that has wireless contact with the recorder and with a server where data is further processed and the results then sent back to the mobile. The recorder itself could also have a large storage capacity and especially in research, it is common that you transfer all the collected data to a computer for processing and analysis.

Watches that you buy are in principle individual and can usually not be used by several different people consecutively.

Blood pressure

Blodtryck kan mätas med hjälp av en manschett runt armen, men det är lite mera omständligt och en del personer upplever obehag när det spänner i armen. Många väljer därför hellre att mäta hjärtfrekvens.

Sweating

n case of emotional reactions and stress, micro-sweating occurs on the skin, which affects the skin's electrical conductivity. In case of stress, the conductivity increases. However, the method is also affected by how much we move and the temperature outdoors.

Stress hormones

Stress hormones can be measured in blood, urine and saliva. You should collaborate with researchers to get reliable results.

Catecholamines

Epinephrine, norepinephrine and dopamine are best measured in the urine. Sampling must be done carefully and that means that it will be quite cumbersome. One needs to have control over the daily amount of urine and time. The urine is then analyzed in a suitable laboratory.

Cortisol

It is most convenient to measure cortisol in saliva. You then need to use special test tubes and it is important that the instructions are followed carefully. The samples are then analyzed in a suitable laboratory. Saliva cortisol is most useful in experimental studies where you have careful control over everything that happens and a very standardized sampling. Cortisol production varies greatly throughout the day and is also affected by food, tobacco, sleep, physical activity, etc. There is a very large variation of cortisol in one person and to an even greater degree between different people. It can therefore be difficult to get clear results because there are many different factors that affect and the normal variation is large. It is an advantage if you take repeated samples of the same persons because the variation will then be smaller. The time of day for sampling is important because the diurnal variation is so great.

The body's own anabolic hormones and the immune system

The anabolic hormones, e.g. growth hormones and sex hormones, have constructive effects. They are released when one rests and sleeps and promotes growth and repair processes in the body and brain. There are links between several hormonal systems and the immune system.

Especially in Japanese studies, positive effects on staying in a forest environment have been investigated and found.

It could be quite complicated to measure and interpret the results. These variables are recommended primarily in specialized research.

Factors related to the metabolic syndrome and risk of cardiovascular disease

BMI - Body Mass Index (kg/m2), waist circumference, blood glucose and blood lipids are affected in a negative direction when you are exposed to prolonged stress.

These effects are mainly caused by the stress hormone cortisol, which aims at mobilizing energy in the form of sugar and fatty acids. This leads to a situation with an increased risk of developing the metabolic syndrome, diabetes and cardiovascular disease. The metabolic syndrome is characterized by increased BMI, abdominal obesity, elevated blood glucose levels and blood lipids. Unhealthy diet, high energy intake and low physical activity also increase the risk of developing the metabolic syndrome.

It is relatively easy to measure these factors, but most often you only see effects after a considerably long time and it can therefore be difficult to demonstrate specific effects due to spending time in natural environments. The physical activity that you often get when you are out in nature also has a positive effect and prevents the metabolic syndrome. Collaboration with medical researchers is recommended.

Text/ Lisbeth Slunga Järvholm (2022)