This study investigated the effects of particulate matter (PM) with aerodynamic diameter 0.02-1 μm (noted as PM 1 ) inhalation during exercise on conduit artery and microvascular function. Inhalation of internal combustion-derived PM is associated with cardiovascular mortality and morbidity. Direct action of PM on the vascular endothelium is likely, as a substantial fraction of ultrafine PM translocates from the alveoli to the circulatory system. Sixteen intercollegiate athletes performed 30 min of exercise while inhaling low or high PM 1 . Flow-mediated brachial artery dilation (FMD) using high-resolution ultrasonography with simultaneous measurements of forearm oxygen kinetics using near infrared spectrophotometry (NIRS) was done before and after exercise. Basal brachial artery vasoconstriction was found after high PM 1 exercise (4.0%, 4.66 ± 0.609 to 4.47 ± 0.625 mm diameter; p = .0002), but not after low PM 1 exercise (−0.3%, 4.66 ± 0.626 to 4.68 ± 0.613 mm diameter). FMD was impaired after high PM 1 exercise (6.8 ± 3.58% for preexercise FMD and 0.30 ± 2.74% for postexercise FMD, p = .0001), but not after low PM 1 exercise (6.6 ± 4.04% for preexercise FMD and 4.89 ± 4.42% for postexercise FMD). Reduction in forearm muscle reperfusion estimated by reoxygenation slope-to-baseline after 4 min cuff ischemia was observed for high PM 1 exercise (55% vs. 3%, p = .0006); no difference was noted for low PM 1 exercise. Brachial artery FMD was significantly correlated to muscle reoxygenation slope-to-baseline (r = .50, p = .005). Acute inhalation of high [PM 1 ] typical of urban environments impairs both systemic conduit artery function and microcirculation. The observed decrease reoxygenation slope-to-baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature.

Both spinal manipulation with thrust and mobilization without thrust procedures produce a profound but transient attenuation of alpha motoneuronal excitability. These findings substantiate the theory that manual spinal therapy procedures may lead to short-term inhibitory effects on the human motor system.

No abstract