Drawing on research across anthropology, environmental physiology and sport science, the paper explores why physically inactive populations may be particularly vulnerable to environmental stress and identifies groups that could be most at risk.
The team, led by Dr Danny Longman, Senior Lecturer in Human Evolutionary Physiology at Loughborough University, alongside Dr Tadej Debevec of the University of Ljubljana and Professor Jan Bourgois of Ghent University, says more attention needs to be given to helping people cope with climatic changes that are already occurring and cannot be avoided in the short term.
They argue that physical activity could play a role in building the body's resilience to environmental stresses associated with events such as heatwaves.
Following the UK's hottest summer on record, rising temperatures and extreme weather mean our bodies are increasingly likely to face conditions that place greater strain on their ability to function.
Published in the European Journal of Applied Physiology, the paper explores how extreme heat and other challenging environmental conditions can affect key systems in the body, including our ability to regulate body temperature, cardiovascular function, and the health and function of our muscles and bones.
It highlights how physical inactivity may make people more vulnerable to these stresses and points to the potential scale of the issue, with around one-third of adults worldwide, approximately 1.8 billion people, not meeting recommended levels of physical activity.
Dr Longman, an expert in human evolutionary physiology, explains that our bodies evolved in environments where regular movement was essential to survival, meaning the sedentary lifestyles common today can have consequences for our physical capacity.
He said:
"For most of human evolutionary history, our survival required regular physical activity through activities such as hunting and gathering. Our bodies therefore evolved to be physically active.
"Our bodies respond to movement by maintaining and developing our muscle, bone and cardiovascular capacity. When we become more sedentary, that stimulus disappears and those systems can deteriorate.
"Regular exercise places manageable stress on the body, encouraging it to adapt. Over time, those adaptations can improve our ability to cope with other forms of physical stress.
"For example, endurance-based exercise can improve cardiovascular health and fitness and our ability to regulate body temperature, while strength training supports muscle function and may also improve cellular responses to heat stress."
Older people, people living with chronic health conditions, outdoor workers and disadvantaged populations are among the groups identified as being particularly vulnerable to the effects of climate-related environmental stress.
As we age, physical capacity and function naturally decline, which can affect the body's ability to respond to stress. Reduced levels of physical activity can further diminish that capacity.
People living in lower-income communities and developing countries can face additional risks due to factors including poor infrastructure, air pollution, densely populated urban environments and fewer resources to protect themselves from extreme conditions.
The researchers say this strengthens the case for accessible, affordable, community-level opportunities for physical activity, with natural spaces potentially playing an important role.
Dr Longman said:
"In modern society, exercise can often be viewed as something that happens indoors, in a gym, a class, swimming pool or other training facility. That can create barriers to exercise, including access and cost.
"Natural environments are the settings in which human physical activity originally evolved, and these spaces could offer opportunities to develop affordable, community-level approaches that encourage people to move and be active."
However, the researchers stress that being physically fit does not remove the risks posed by extreme environmental conditions.
People such as outdoor workers, athletes and military personnel can be highly physically fit but may experience much greater environmental stress because of the conditions in which they work or exercise. Different groups will therefore require different approaches to reducing their risk.
The researchers also emphasise that encouraging physical activity is not a substitute for tackling climate change, but that as we are now living with the effects, building our resilience must be made a priority.
Dr Longman said:
“Exercise won’t reduce the causes of climate change, but with some effects of climate change already deemed irreversible, creating healthier and more physiologically resilient populations should form part of wider climate adaptation strategies.”
ENDS