Traffic, crowds and obstacles aren't the only things joggers need to be aware of when pounding the city pavement.
Belgium research has shown that people who exercise on city streets have higher levels of inflammation and score lower on brain tests than people who exercise in the country.
Dr Romain Meeusen, the head of Human Physiology and Sports Medicine at Vrije Universiteit Brussel in Belgium, compared 15 urban joggers with nine rural runners.
For 12 weeks, the groups alternated between walking and running on three days a week between 12 and 1.30pm.
They were then tested for inflammation, fitness and cognitive function.
The researchers found that the city joggers did not get the same exercise-induced brain benefits –– such as comprehension and brain plasticity –– as the country runners.
"Aerobic training in an urban environment with high traffic-related air pollution increased inflammatory biomarkers and, in contrast to aerobic training in a rural environment, cognitive performance … did not improve," Dr Meeusen wrote.
But considering our bodies have recovery mechanisms to help undo the damage of inflammation, Dr Meeusen said exercising is still better for health than not doing any.
Professor Andrew Creswell, a spokesperson for Exercise and Sports Science Australia, told ninemsn that the study was too limited to draw strong conclusions.
"We know that exercising has very good effects in brain function," he said.
"Clearly exercising in fresh air is better than exercising in poor air and you don't really want to go running next to freeways."
But he said there are many reasons why the country people might have performed better in cognitive tests, and suggested that Australia's pollution levels are rarely high enough to cause damage.
"It's almost a scare tactic saying if you live in the city, don't go out and exercise because you're going to get pollution. For someone living in Australia that is probably not going to happen," he said.
"But maybe somewhere in Beijing it's possible because of the quality of air and weather conditions."