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840917 
Journal Article 
Review 
The Coronary Circulation in Exercise Training 
Laughlin, MH; Bowles, DK; Duncker, DJ 
2012 
Yes 
American Journal of Physiology: Heart and Circulatory Physiology
ISSN: 0363-6135
EISSN: 1522-1539 
302 
1 
H10-H23 
English 
21984538 
WOS:000298643800002 
Exercise training (EX) induces increases in coronary transport capacity through adaptations including increased arteriolar diameters and/or densities and changes in reactivity of coronary resistance arteries. EX increases capillary exchange capacity through angiogenesis of new capillaries at a rate matched to EX-induced cardiac hypertrophy so that capillary density remains normal. However, after EX exchange area is greater at any given flow due to altered coronary vascular resistance and matching of exchange area and blood flow distribution. The improved capillary blood flow distribution appears to be the result of structural changes in the coronary tree and alterations in vasoreactivity of coronary resistance arteries. EX also alters α receptor responsiveness. Of interest, α and ß tone appears to be maintained in the coronary microcirculation in the presence of lower circulating catecholamine levels due to increased receptor responsiveness to adrenergic stimulation. EX also alters other vasomotor control processes of coronary resistance vessels. For example, coronary arterioles exhibit increased myogenic tone after EX, likely due to a calcium-dependent PKC signaling-mediated alteration in voltage-gated calcium channel activity in response to stretch. Conversely, EX augments endothelium-dependent vasodilation (EDD) throughout the coronary arteriolar network and in the conduit arteries in coronary artery disease (CAD). The enhanced EDD appears to result from increased nitric oxide (NO) bioavailability due to changes in NO synthase expression/activity and decreased oxidant stress. EX does not stimulate growth of collateral vessels in the normal heart. However, if exercise produces ischemia there is evidence that collateral growth can be enhanced. Evidence that EX reverses or slows progression of lesion development in CAD is not strong due because prospective trials have included other lifestyle changes and treatment strategies. Thus, while it appears that EDD, evidence that EX reverses or slows progression of CAD is not conclusive at this time. 
atherosclerosis; coronary blood flow; endothelium; physical activity; smooth muscle