Mood and selective attention in the cold: the effect of interval versus continuous exercise

Both mood and cognitive function are altered in cold environments. Body warming through exercise may improve Stroop interference score and lessen total negative mood. The purpose of this study was to determine the effect of equal caloric bouts of interval (INT) and continuous (CONT) exercise on mood and selective attention in the cold. Eleven youngmen underwent two experimental trials in 5°C air.Both trials consisted of 90 min acute cold exposure (ACE), 30 min exercise (INT vs. CONT), and 60 min recovery (REC). The Profile of Mood States (POMS) and Stroop Color Word Test caffeine ingested throughout the day would elicit a similar response as one large bolus dose ingested 1 h prior to exercise on antigen-stimulated NK cell CD69 expression following strenuous intermittent exercise. In a randomized cross-over design, 15 healthy males completed six 15 min blocks of intermittent running consisting of maximal sprinting interspersed with less intense running and walking. Participants had ingested either 0 (PLA), 2 mg kg-1 body mass (BM) caffeine on three separate occasions during the day (39 CAF) or one dose of 6 (19 CAF) mg kg-1 BM caffeine, 1 h before exercise. At 1-h post-exercise, the number of antigen-stimulated CD3-CD56? cells expressing CD69 was lower on 19 CAF compared with PLA [P<0.05; PLA: 42.0 (34.0) 9 106 cells L-1, 19 CAF: 26.2 (25.0) 9 106 cells L-1], with values on 19 CAF at this time point remaining close to pre-supplement. 19 CAF tended to attenuate the exercise-induced increase in geometric mean fluorescence intensity of CD69 expression on antigen-stimulated CD3-CD56? cells 1-h post-exercise [P = 0.055; PLA: 141 (28)%, 19 CAF: 119 (20)%]. These findings suggest that although one large bolus dose of caffeine attenuated the exercise-induced increase in antigen-stimulated NK cell CD69 expression 1 h following strenuous intermittent exercise, this attenuation at no point fell below pre-supplement values and caffeine does not appear to depress NK cell CD69 expression.