Effects of a proposed challenge on effort sense and cardiorespiratory responses during exercise.

PURPOSE: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency. METHODS: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min. RESULTS: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change. CONCLUSION: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.

The effectiveness of a point-of-decision prompt in deterring sedentary behavior.

Individuals using a university library were observed using stairs or elevators to travel up one to three floors. After a baseline assessment, a sign was posted by the elevator to discourage elevator use over a five-week period. A hierarchical log linear analysis indicated that stair use increased significantly after the intervention moderated by day of the week, sex, and age. The study suggests that point-of-decision prompts to deter sedentary activity may be effective.

Effects of low-volume resistive exercise on beta-endorphin and cortisol concentrations.

It has been recently suggested that high and sustained lactate levels may elicit increases in peripheral B-EN concentrations (16). We have observed elevated and sustained lactate concentrations in response to a low-volume resistive exercise protocol (14) that were similar to those from other exercise protocols that produced elevated beta-endorphin (B-EN) concentrations. Thus, the purpose of the study was to determine the effects of a low-volume (21,700 J) resistive exercise repetition maximum (RM) protocol using weight machines on peripheral lactate, B-EN and cortisol concentrations. Subjects completed 3 sets of bench press, lat-pull, leg extension, and leg curl exercise at a 10-RM load. Blood samples were collected and rating of perceived exertion (RPE, 15-point Borg scale) was assessed before exercise (-40 and -10 min), after each exercise, and after the exercise session (+ 35 min); blood samples were collected at 7 additional post-exercise times. RPE increased significantly throughout the exercise. Lactate concentrations rose significantly to peak at 8.54 mM at LE. B-EN and cortisol concentrations (-10) of 4.63 +/- 0.54 pmol.l-1 and 12.09 +/- 1.44 micrograms.dl-1, respectively, were not significantly elevated over time. The data suggest that a low-volume resistive exercise protocol using weight machines elevates lactate concentrations without altering B-EN and cortisol concentrations.

Physical activity determinants: a social cognitive approach.

This paper presents Bandura's social cognitive theory as a utilitarian framework to study the determinants of physical activity. I provide an overview of social cognitive theory assumptions and stress the importance of studying self-efficacy in concert with other key cognitive processes. Research addressing when there is a cognitive-behavioral relationship is identified. The paper concludes with the practical implications of social cognitive theory.

Mood alteration from treadmill running and its relationship to beta-endorphin, corticotropin, and growth hormone.

We examined the effects of running on mood alteration in males and females and its relationship to changes in beta-endorphin (B-EN), corticotropin (ACTH), and growth hormone (GH). Thirteen males and ten females ran on a treadmill for 30 min at 80% of previously determined maximum heart rate. Five plasma samples were obtained through an indwelling catheter before exercise (-30 and 0 min), during exercise (15 min), at exercise completion (+30 min), and after 30 min of recovery (R30); the Profile of Mood States (POMS) inventory was administered at -30 and +30. Composite mood improved after the run for both males and females withput concomitant rise in B-EN. For males but not females, an increase in mood was associated with lower B-EN (r = 0.65) and ACTH (r = 0.65) and this relationship was also significant prior to exercise for B-EN (r = 0.74) and ACTH (r = 0.81). It appears that an increase in peripheral beta-endorphin concentration may not be a major contributor to improved mood in response to exercise, but is an indicator of negative mood in males.