Training outside in an urban environment may not be as beneficial for a person's health as they might hope, suggests research.
Romain Meeusen (Vrije Universiteit Brussels, Belgium) and colleagues found that volunteers who trained (walking and running) three times a week in an urban environment for 12 weeks had higher levels of inflammation and lower scores on the Stroop cognition task than those who trained in a rural environment.
"Particulate Matter (PM) exposure is linked to inflammation, neuroinflammation, and cognitive decline, whereas aerobic training improves cognition," write Meeusen and team in Medicine and Science in Sports and Exercise.
To investigate the effects of ultrafine (UF) PM exposure during aerobic training, the researchers recruited two groups of untrained (no training for at least 3 months) volunteers between 18 and 60 years, half of whom underwent training in an urban area (n=15) with exposure to traffic pollution and other UFPM and half of whom trained in a rural setting (n=9).
The researchers measured various factors before and after the 12-week program including aerobic fitness (Cooper test), serum Brain-Derived Neurotrophic Factor (BDNF) - thought to mediate exercise-associated improvements in cognition and performance, total and differential leukocyte counts, exhaled levels of nitric oxide (eNO), and cognitive performance - measured using the Stroop task, Operation Span, and Psychomotor Vigilance Task tests. UFPM levels were also measured during each training session.
The team found that although levels of fitness improved to a similar degree in both groups over the 12 weeks, levels of leukocytes, eNO, and neutrophils increased significantly in the urban but not the rural group, indicating increased levels of inflammation.
Reaction times, as measured by the Stroop task test, improved in the rural, but not the urban group, whereas no effects of either training location were observed on BDNF levels or on results from the Operation Span and Psychomotor Vigilance Task tests.
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