Sport and thermal comfort, recommendations from the world of research

Research enables the preparation of guidelines to improve the comfort sensation of the occupants of a building. While the typical scope of such research is residential and office comfort, the same approach can be used in sports centres. IREC carried out a thorough analysis of the current regulations of thermal comfort and indoor air quality in several countries. This has been coupled with a monitoring campaign to collect data on temperature, humidity, and air quality to understand the indoor quality of gyms in Catalonia. The monitoring included a comfort survey to users with the goal to combine objective measured data with the subjective perception of occupants. The results revealed that most users experience sensations of heat during physical activity, which influence their perception of humidity and air quality. The conclusions of the study have been converted to guidelines to improve the planning and management of sports facilities, with the final goal of creating healthier and more comfortable environments for users.

What is indoor environmental quality?

Indoor environmental quality is the scientific discipline that studies the well-being of people inside a building considering the activities they develop. The discipline impact is relevant considering that people spend 90% of their time in buildings. Its main findings showcase that indoor environmental conditions are important for learning, health, well-being, and work patterns. This is equally applicable to sports practice. In all cases, indoor environmental quality depends on two groups of indicators, personal parameters, and environmental parameters.

The environmental parameters consider five distinct aspects (Figure 1). First, two aspects related to the occupants' sensation of their thermal exchanges with the environment: thermal comfort (affected by temperature and air speed) and relative humidity. Two other aspects account the acoustic comfort, related to the noise level, and the visual comfort, related to the amount of light needed to carry out activities. Finally, the last aspect are the environmental parameters that measure the air quality. These parameters refer to the purity of indoor air, which must have low concentrations of pollutants such as: suspended particulate matter (PMx), formaldehyde, Volatile Organic Compounds (VOCs), and a concentration of CO₂ compatible with human activities. Good air quality reduces the possibility of transmitting infections and having respiratory problems.

Figure 1. Indoor environment quality parameters.

On the other hand, indoor environmental quality depends also on personal parameters. These include the metabolic rate of the activity that occupants are engaged in, the insulation provided by their clothing, gender, age, and state of health. The influence of these numerous factors makes it challenging to determine the conditions that would make a majority of people feel thermally comfortable. Therefore, the same environmental parameters can generate different perceptions of indoor environmental quality depending on the person and the activity performed.

IREC research and sports halls

Over the years, IREC has studied lighting and thermal comfort in different sport halls in Catalonia, comfort conditions in swimming pools and, as of 2022, research has focused on gyms. In these, a wide variety of activities are carried out. There are intense directed activities (such as zumba, dance, body pump, ...) and others that are more relaxed (various types of yoga, pilates, stretching, hypopressive). Moreover, in the category of gyms we find the fitness rooms, all those spaces where activities such as free weights, functional training and cardio activities are performed. This type of room is characterized by a repetitiveness of the activities, with moments of pause between one and the other. In addition, in a fitness room occupants can be doing different exercises simultaneously, with the consequent diversity of metabolic activity levels. This poses an additional challenge from a comfort point of view.

Figure 2. Activities classification according to metabolic intensity.

Regulations in force in several countries.

As a first step of the study, the research team analysed the different regulations of European and foreign countries in terms of environmental parameters and comfort in rooms intended for sports use. The regulation of acceptable ranges of temperature, relative humidity and CO₂ is common for offices, health and educational centres. However, regulations or recommendations concerning thermal comfort and air quality in sports centres are infrequent. Moreover, the existing ones use heterogeneous parameters and ranges. The most frequently regulated parameters are temperature and relative humidity. The former has very different values depending on the regulations, while the latter has consistent values. Other less standardized parameters are visual comfort, acoustic comfort, and air quality. In IREC’s local context, Spain has no specific regulations on the quality of the indoor environment for sport facilities.

The monitoring campaign and the user survey.

IREC conducted a monitoring campaign of environmental parameters in several gyms in Barcelona and surroundings. The objective was to record indoor environmental quality parameters and compare them with the users' perception of comfort. The centres were monitored with portable sensors for temperature, relative humidity, CO₂ concentration and suspended particles for a period of two weeks.

Monitoring in spaces used daily by many people engaged in physical activity is a significant challenge. Data collection must be done without disturbing the normal use of the facility. Furthermore, it is important to involve the facility staff and users in the comfort surveys that accompany the monitoring. IREC has therefore developed an indoor environment quality monitoring protocol. This indicates the number and type of sensors recommended for the study according to the type of room, as well as their placement in the space. Obviously, the characteristics of the rooms may make optimal placement difficult. Nevertheless, the proposed general rules are the following:

·         Place the sensors between 1 and 2 m in height.

·         Avoid local air injection points, as well as direct solar radiation.

·         In the case of rooms with more floors, place a sensor in each of them.

·         Duplicate sensors and distribute them symmetrically to provide redundancy, capture an average of the state of the room and possible differences between points.

During the monitoring campaign, the IREC team has also collected data on room occupancy, i.e., the number of occupants in each room during the activities. This type of data was either shared by the gyms, which usually have it available through an app or a website used to book the activities/classes. Alternatively, coaches usually keep track on the number of users attending their activities. In the case this data was not available, occupancy sensors were used at the entrances of the rooms to count the number of people entering the rooms.

The monitoring was carried out from November 2022 to July 2023. Therefore, data from different seasons and weather conditions was available. During this campaign, directed activities, spinning and fitness rooms were monitored, collecting data during the periods of occupation according to the type of sports activities. Additionally, the monitoring was complemented with surveys in digital format to collect information on the comfort of the occupants. This was done by hanging different posters with a QR code that gave access to a survey form specific for each room being monitored. These contained a short list of questions regarding the perception of the thermal situation, humidity, air quality, lighting, and noise with answers on a scale of values (Likert scale). This type of survey in digital format made it possible to collect responses without the need to interrupt the users' activities with questions asked physically by a person, which can also affect the response of the interviewees.

Analysis of the data collected

The most interesting result of the study was the link between the subjective feeling of the occupants and the environmental data collected during the monitoring. Accordingly, IREC’s team has proposed ranges of environmental values that maximize the positive responses on environmental comfort.

After analysing more than 230 responses, it stands out that most of the occupants tend to have a medium or intense sensation of heat when they are doing some kind of physical activity in the monitored rooms (Figure 3). In fact, the highest percentage of responses represents warm sensations, followed by a minority of respondents who reported a neutral thermal sensation and a few respondents who reported cold sensations. The peak of comfort sensation is found for responses collected at a temperature below 21°C, although it still represents only 37.5% of the surveyed users. However, for higher temperatures, most people feel "hot", with the majority of responses being in the "very hot" range. Another very interesting result is that occupants do not have an accurate perception of humidity or CO₂ concentration (i.e., the feeling of stuffy air). On the contrary, they tend to relate these two variables respectively to temperature and to odour. In fact, lower temperatures improved the occupants' sense of humidity, thus their perception that the air was cleaner.

Figure 3. Sport room temperature (black line) and occupants thermal comfort answers (colored dots). The horizontal grey area represents the temperatures range recommended by the standards. The vertical grey areas represent the periods with occupancy in the room.

Recommendations from the study

The conclusions of the monitoring, surveys and analysis of the regulations were used to prepare a guide of good practices to improve the quality of the indoor environment quality and minimize energy consumption. In the case of rooms where low-intensity metabolic activities and fitness rooms are performed, it is recommended to set the heating to a setpoint temperature of 20.5°C and the cooling to 25°C. This means that there is no need to expend energy when the temperature is between these two values. For high intensity activities, it is advisable to lower the range by 1 degree, then set heating to 19.5ºC and cooling to 24ºC. High metabolic intensity includes activities such as zumba, dance, spinning, toning, fitbox, step, GAC, Body Pump, karate, functional training, cardio and aerobic activities. Low metabolic intensity activities include Pilates, various types of yoga, hypopressive exercises, and stretching, among others. In any case, the relative humidity should not fall below 40% and not rise above 60%, according to the results of monitoring and most of the regulations analysed. The maximum recommended CO₂ concentration value is 1200ppm absolute.

Apart from that, it is recommended to organize the activities so that those with similar metabolic intensities are held in the same spaces. This allows to optimize the heating of the rooms with low intensity activities in winter and to concentrate the cooling in the high intensity activities rooms in summer, also avoiding unnecessary air conditioning of multiple spaces. In the case of having only one room in the gym, grouping similar activities in the same time frame will help in maintaining constant temperature needs and avoid unnecessary heating and cooling cycles. For example, low intensity activities can be performed in the afternoon of one day and in the morning of the following day, and high intensity activities can be performed after them. Regarding air-conditioning times, it is recommended to start cooling the spaces in summer only 30 minutes before the start of classes with a setpoint temperature of 25ºC or 24ºC (depending on the activity). This will reduce the sensation of heat and minimize cooling time. In winter, it would be better to heat the spaces 30 minutes before the start of activities, or directly at the start time. The set point temperature should be 20.5°C or 19.5°C (depending on the activity). In relation to air quality, if mechanical ventilation is not sufficient, it is recommended to open the windows between classes and thus lower the CO₂ concentration. This is only advisable in areas of low pollution that allow renewal with outside air but avoiding the introduction of pollutants and suspended particles.

The aim of the study was to provide sports facility staff with a guide supported by scientific evidence on how to manage the indoor environmental quality of sports halls. Sports facilities that offer a good indoor environment quality will allow users to do sport in healthy conditions, improve their performance and offer them a satisfactory experience. The results of the study are presented in a scientific article in Indoor Air journal [1] and the guide of good practices is available in IREC public Zenodo repository [2].

References

[1]     L. Borghero, J. Ortiz, J. Salom (2024). Calculating comfort indexes and applying comfort models to predict thermal sensation vote in sports centres. Indoor Air (2024). https://doi.org/10.1155/1970/9142303.

[2]     L. Borghero, S. Escudero, J. Romaní, J. Ortiz, J. Salom (2024). Protocol de Monitoratge de la Qualitat Ambiental Interior per Sales Esportives. Zenodo. https://doi.org/10.5281/zenodo.10650041.