To determine the effect of exercise on the in vivo formation of circulating platelet aggregates in patients with severe coronary artery disease (CAD), platelet aggregate ratios (PAR) (normal 0.8-1.1) were measured immediately before and after treadmill exercise and 30 minutes after exercise in 17 CAD patients (group 1, mean age 55 years), 12 age-matched normal subjects (group 2), and 13 young normals (mean age 27 years, group 3). Coronary patients had lower resting PAR than group 3 (0.79 ± 0.05 vs 0.98 ± 0.03; p < 0.01), while group 2 had an intermediate value 0.86 4-0.04 (p > 0.05 vs CAD and group 3). Immediately after exercise, group I PAR declined from 0.79 i 0.05 to 0.53 ± 0.04 (p < 0.001), while groups 2 and 3 were unchanged (p > 0.05; both p < 0.001 vs group 1); 30 minutes after exercise, PAR in group 1 rose to 0.66 ± 0.05 (p < 0.05 vs pre-and immediately postexercise); groups 2 and 3 remained unchanged vs pre-and immediately postexercise (p > 0.05; both p < 0.001 vs group 1). Six group 1 patients received 1300 mg aspirin daily for 10 days and repeated the protocol. Resting PARs were unchanged (p > 0.05) from resting values without aspirin. The exercise-induced decline in PAR was attenuated by aspirin: without aspirin, 0.73 ± 0.02 preexercise to 0.54 ± 0.04 postexercise; with aspirin, 0.73 ± 0.03 to 0.82 ± 0.03 (p < 0.05 vs no aspirin). These data indicate that platelet aggregation occurs with exercise in CAD. In addition, these data suggest that aspirin exerts a significant inhibitory effect on exercise-induced platelet aggregation in CAD patients.

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The statistical relation between two events influences the perception of how well one event relates to the presence or absence of another. The simultaneous absence of both events, just like their mutual occurrence, is theoretically relevant for describing their contingency. However, humans tend to weight co-occurring information more heavily than co-absent information. We explored the relevance of co-absent events by varying the duration and frequency of trials without stimuli. In three experiments, we used a rapid trial streaming procedure, and found that the perceived association between events is enhanced with increased frequency of co-absent events. Duration of co-absent events did not play as strong role on judgments of association as did frequency. These findings suggest ways in which the benefits of trial spacing, which are effectively co-absence events, could be preserved without increasing total training time. Specifically, the present results suggest that the benefits of distributed practice can be obtained without increasing the length of the training session by shortening the intervals between events. We also discuss five potential accounts of how the co-absent experience is processed: contingency sensitivity, a memory testing effect, associative interference, reduced cognitive load, and consolidation.

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