Racial differences in exercise recovery 
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https://cdn.pixabay.com/photo/2012/10/10/04/41/discrimination-60512_1280.jpg
According to the results of [this study](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516681/) the psychological impact of racism may have a negative impact on physiological health. The sympathetic nervous system is associated with "fight or flight" response while the parasympathetic nervous system is associated with "rest and digest" response. These responses are from the autonomic nervous system and so they are beyond the ability of the brain to consciously control.

The study found statistically significant difference between black and white exercise recovery based on what the study calls ERI (exercise recovery index). The ERI contains heart rate/VO2 plateau. The subjects in the study were obese adolescent females with the only obvious difference being their race. 

I always say "race isn't scientifically real" but this does not mean the psychological impact of racism is not real. Racism as a sociological and psychological condition is clearly capable of having real physical effects which can damage health. The most obvious example would be higher levels of psychological stress experienced by a certain race more than another race. This highlights the actual physical damage racism could cause (although the study does not trace the statistically significant differences to racism specifically).

Heart rate variability and other simple statistical measures can be used to monitor (theoretically) sympathetic nervous system over activity. The problem is this does not determine the exact cause of the activity. It could be the case that it is critical for some people to avoid a high stress environment, high stress job or atmosphere. It could be genetically determined, where some people just can handle for example more air pollution or bad food than others. We cannot rule out psychological stress creating physiological stress (and under recovery) but this is an area of research worthy of more investigation. 

What impact does the environment have on autonomic nervous system dysfunction? 



References
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Franco, R. L., Privett, S. H., Bowen, M. K., Acevedo, E. O., Arrowood, J. A., Wickham, E. P., & Evans, R. K. (2015). Sympathetic activity assessed during exercise recovery in young obese females. The Journal of pediatrics, 167(2), 378-383.

Amen-Ra, N. S. S., Velasco-Mondragon, E., Hossain, M. B., & Bronner, Y. (2012). Energy expenditure differs between black and white Americans: implications for obesity prevention research. Food and Nutrition Sciences, 3(07), 914.