Editing Autonomic nervous system (section)

==Caffeine effects==
[[Caffeine]] is a [[bioactive compound|bioactive ingredient]] found in commonly consumed beverages such as coffee, tea, and sodas. Short-term physiological effects of caffeine include increased [[blood pressure]] and sympathetic nerve outflow. Habitual consumption of caffeine may inhibit physiological short-term effects. Consumption of caffeinated espresso increases parasympathetic activity in habitual caffeine consumers; however, decaffeinated espresso inhibits parasympathetic activity in habitual caffeine consumers. It is possible that other bioactive ingredients in decaffeinated espresso may also contribute to the inhibition of parasympathetic activity in habitual caffeine consumers.<ref>{{cite journal|last1=Zimmerman-Viehoff|first1=Frank|last2=Thayer|first2=Julian|last3=Koenig|first3=Julian|last4=Herrmann|first4=Christian|last5=Weber|first5=Cora S.|last6=Deter|first6=Hans-Christian|title=Short-term effects of espresso coffee on heart rate variability and blood pressure in habitual and non-habitual coffee consumers- a randomized crossover study|journal=Nutritional Neuroscience|date=May 1, 2016|volume=19|issue=4|pages=169–175|doi=10.1179/1476830515Y.0000000018|pmid=25850440|s2cid=23539284}}</ref>

Caffeine is capable of increasing work capacity while individuals perform strenuous tasks. In one study, caffeine provoked a greater maximum [[heart rate]] while a strenuous task was being performed compared to a [[placebo]]. This tendency is likely due to caffeine's ability to increase sympathetic nerve outflow. Furthermore, this study found that recovery after intense exercise was slower when caffeine was consumed prior to exercise. This finding is indicative of caffeine's tendency to inhibit parasympathetic activity in non-habitual consumers. The caffeine-stimulated increase in nerve activity is likely to evoke other physiological effects as the body attempts to maintain [[homeostasis]].<ref>{{cite journal|last1=Bunsawat|first1=Kanokwan|last2=White|first2=Daniel W|last3=Kappus|first3=Rebecca M|last4=Baynard|first4=Tracy|title=Caffeine delays autonomic recovery following acute exercise|journal=European Journal of Preventive Cardiology|date=2015|volume=22|issue=11|pages=1473–1479|doi=10.1177/2047487314554867|pmid=25297344|s2cid=30678381|doi-access=free}}</ref>

The effects of caffeine on parasympathetic activity may vary depending on the position of the individual when autonomic responses are measured. One study found that the seated position inhibited autonomic activity after caffeine consumption (75&nbsp;mg); however, parasympathetic activity increased in the supine position. This finding may explain why some habitual caffeine consumers (75&nbsp;mg or less) do not experience short-term effects of caffeine if their routine requires many hours in a seated position. It is important to note that the data supporting increased parasympathetic activity in the supine position was derived from an experiment involving participants between the ages of 25 and 30 who were considered healthy and sedentary. Caffeine may influence autonomic activity differently for individuals who are more active or elderly.<ref>{{cite journal|last1=Monda|first1=M.|last2=Viggiano|first2=An.|last3=Vicidomini|first3=C.|last4=Viggiano|first4=Al.|last5=Iannaccone|first5=T.|last6=Tafuri|first6=D.|last7=De Luca|first7=B.|title=Espresso coffee increases parasympathetic activity in young, healthy people|journal=Nutritional Neuroscience|date=2009|volume=12|issue=1|pages=43–48|doi=10.1179/147683009X388841|pmid=19178791|s2cid=37022826}}</ref>