Thermoregulatory Control and Exercise in Older Adults
Differences between 50–70 Year Olds and the Over 70s
I had many years playing squash at a national level, and subsequently in fitness coaching for seniors, and had noticed in myself and others the reduced amount of sweating as we got older, even with the same amount of effort put into the exercise.
Ageing is often associated with decreased physiologic function, including a decreased ability to regulate body temperature effectively during heat stress.
This belief points to epidemiological studies which consistently show a relationship between age, morbidity and mortality during climatic heat waves, and also I note that many laboratory studies have demonstrated how older individuals respond to an imposed heat challenge with higher core temperatures and heart rates, lower sweating rates, and a greater loss of body fluid compared to younger individuals.
What is not clear, however, is whether chronologic age per se causes poor heat tolerance, or whether other factors which change concomitantly with advancing age play a larger role than age itself.
As the global population ages, understanding how older adults regulate body temperature during exercise becomes increasingly important. Thermoregulation, the body’s ability to maintain its core temperature, is crucial for preventing heat-related illnesses, especially during physical activity.
Let’s examine the differences in thermoregulatory control between two age groups: 50–70 year olds and those over 70, highlighting the scientific basis for these differences. I use these groups because, sadly, I’m amongst them.
The Basics of Thermoregulation
Thermoregulation involves several physiological processes, including sweating and skin blood flow (SkBF). When the body heats up during exercise, it dissipates excess heat through these mechanisms. However, ageing affects these processes, leading to differences in how older adults manage heat stress.
Thermoregulatory Differences in 50–70 Year Olds
1. Sweating Response: Research indicates that individuals aged 50–70 can maintain a relatively effective sweating response, although it may be slightly diminished compared to younger adults. This age group can still acclimate to heat stress through regular aerobic exercise, which enhances their sweating rate and SkBF at a given core temperature.
2. Skin Blood Flow: While there is a reduction in SkBF with age, those in the 50–70 age range can still manage heat dissipation effectively. Studies show that healthy, fit individuals in this group exhibit similar core-to-skin thermal gradients as younger adults, allowing for adequate convective heat transfer.
3. Heat Acclimation: Middle-aged adults can acclimatise to hot environments similarly to younger individuals, and regular aerobic training improves their thermoregulatory responses, making them capable of handling heat stress during exercise.
Thermoregulatory Challenges in the Over 70s
1. Reduced Sweating Capacity: For those over 70, the ability to sweat diminishes significantly. This reduction is due to age-related changes in sweat gland function and density, and consequently, older adults in this age group store more body heat during exercise, increasing their risk of heat-related illnesses.
2. Decreased Skin Blood Flow: The over 70s experience a more pronounced decline in SkBF. This reduction impairs their ability to dissipate heat through the skin, leading to higher core temperatures during physical activity.
The combination of reduced sweating and SkBF makes thermoregulation more challenging for this age group.
3. Behavioural Thermoregulation: Older adults often have a diminished perception of thermal discomfort, which can hinder their ability to adapt behaviourally to heat stress.
They may not feel the need to seek shade, increase fluid intake, or remove excess clothing, further exacerbating their risk of heat-related issues.
Practical Implications for Exercise
Given these differences, I have always recognised that it is crucial to tailor exercise recommendations for older adults to ensure their safety and well-being, and this advice was always passed down to trainee fitness coaches when dealing with older age groups. The instructions included:
1. Hydration: Emphasize the importance of adequate fluid intake before, during, and after exercise. Older adults should be encouraged to drink water regularly, even if they do not feel thirsty, as their perception of thirst may be diminished.
2. Exercise Timing: Recommend exercising during cooler parts of the day, such as early morning or late evening, to minimize heat exposure. Avoiding peak heat hours can significantly reduce the risk of heat stress.
3. Clothing: Advise wearing lightweight, breathable clothing that allows for efficient sweat evaporation. Light-coloured clothing can also help reflect sunlight and keep the body cooler.
4. Gradual Acclimation: Encourage a gradual increase in exercise intensity and duration to allow the body to acclimate to heat stress. This approach is particularly important for those over 70, who may need more time to adapt.
5. Monitoring: Suggest regular monitoring of body temperature and heart rate during exercise. Using wearable technology can help older adults keep track of their physiological responses and adjust their activity levels accordingly.
6. Cooling Strategies: Implement cooling strategies such as using fans, taking cool showers, or applying cold packs to key areas like the neck and wrists. These methods can help lower body temperature and prevent overheating.
Understanding the thermoregulatory differences between 50–70 year olds and those over 70 is essential for promoting safe and effective exercise practices among this group, and while middle-aged individuals can still maintain relatively effective thermoregulation, those over 70 face greater challenges due to reduced sweating capacity and SkBF.
By being sensible and adopting tailored exercise recommendations and cooling strategies, we older adults can continue to enjoy the benefits of physical activity while minimizing the risks associated with heat stress.
References:
The Older Athlete: Exercise in Hot Environments (gssiweb.org)
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