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PURPOSE: The objective of this study is to examine risk taking and risk perception associations with perceived exertion, pacing, and performance in athletes. METHODS: Two experiments were conducted in which risk perception was assessed using the domain-specific risk taking (DOSPERT) scale in 20 novice cyclists (experiment 1) and 32 experienced ultramarathon runners (experiment 2). In experiment 1, participants predicted their pace and then performed a 5-km maximum effort cycling time trial on a calibrated Kingcycle mounted bicycle. Split times and perceived exertion were recorded every kilometer. In experiment 2, each participant predicted their split times before running a 100-km ultramarathon. Split times and perceived exertion were recorded at seven checkpoints. In both experiments, higher and lower risk perception groups were created using median split of DOSPERT scores. RESULTS: In experiment 1, pace during the first kilometer was faster among lower risk perceivers compared with higher risk perceivers (t(18) = 2.0, P = 0.03) and faster among higher risk takers compared with lower risk takers (t(18) = 2.2, P = 0.02). Actual pace was slower than predicted pace during the first kilometer in both the higher risk perceivers (t(9) = -4.2, P = 0.001) and lower risk perceivers (t(9) = -1.8, P = 0.049). In experiment 2, pace during the first 36 km was faster among lower risk perceivers compared with higher risk perceivers (t(16) = 2.0, P = 0.03). Irrespective of risk perception group, actual pace was slower than predicted pace during the first 18 km (t(16) = 8.9, P < 0.001) and from 18 to 36 km (t(16) = 4.0, P < 0.001). In both experiments, there was no difference in performance between higher and lower risk perception groups. CONCLUSIONS: Initial pace is associated with an individual's perception of risk, with low perceptions of risk being associated with a faster starting pace. Large differences between predicted and actual pace suggest that the performance template lacks accuracy, perhaps indicating greater reliance on momentary pacing decisions rather than preplanned strategy.

This research examined the haematological and immunological responses of quadruplicate groups of juvenile (∼400 g initial weight) Atlantic salmon (Salmo salar L.) that had each been fed daily to satiation for 12 weeks one of three high-energy extruded diets of identical composition except for the supplemental dietary lipid (234.7 g kg−1) source. The three experimental diets varied in the composition of supplement lipid; diet 1 contained 100% anchovy oil (AO), while diets 2 and 3 replaced 29.8% and 59.7% of the AO (respectively) with a 1:1 blend of canola oil (CO) and poultry fat (PF). Immediately following the feeding trial, a random sample of fish from each diet was sampled for determination of baseline levels of various haematological and immunological parameters. Thereafter, duplicate diet groups were vaccinated (against Listonella anguillarum) and reared on their respective experimental diets for an additional 4 weeks. At that time, the remaining fish were sampled similarly, and the different parameters were measured again. Comparisons between the different diet treatment groups were made before and after vaccination. There were no significant diet treatment effects at either sample time, for haematocrit, differential leucocyte counts, erythrocyte counts, serum hemolytic activity or head kidney leucocyte respiratory burst activity. The fish fed diet 1 however, did show significantly higher post-vaccination levels of peripheral blood leucocyte respiratory burst activity and higher serum antibody titres against L. anguillarum. The results suggest that the relatively low n-6/n-3 fatty acid ratios in the muscle and presumably other tissues of fish fed diet 1, may have resulted in a reduced production of immunocompromising eicosanoids than were produced in fish ingesting the other two diets that were based in part on the different amounts of the CO and PF blend. Long-term studies are required to confirm this possibility.

This study assessed the suitability and cost efficacy of an equal blend of canola oil (CO) and poultry fat (PF) as a supplemental dietary lipid source for juvenile Atlantic salmon. Quadruplicate groups of Atlantic salmon (∼400 g) held in 4000 L outdoor fibreglass tanks supplied with running (35–40 L min−1), aerated (dissolved oxygen, 7.88–10.4 mg L−1), ambient temperature (8.6–10.9°C) sea water (salinity, 26–35 g L−1) were fed twice daily to satiation one of three extruded dry pelleted diets of equivalent protein (488–493 g kg−1 dry matter) and lipid (267–274 g kg−1 dry matter) content for 84 days. The diets were identical in composition except for the supplemental lipid (234.7 g kg−1) source viz., 100% anchovy oil (AO; diet COPF-0), 70.2% AO and 29.8% CO and PF (diet COPF-30), and 40.3% AO and 59.7% CO and PF (diet COPF-60). Atlantic salmon growth rate, feed intake, feed efficiency, protein and gross energy utilization, percent survival and whole body and fillet proximate compositions were not affected by diet treatment. Cost per kilogram weight gain was about 10% less for fish fed diet COPF-60 than for diet COPF-0. Percentages of saturated fatty acids in dietary and fillet lipids varied narrowly. Moreover, percentages of 18:1n-9, monounsaturated fatty acids, 18:2n-6, n-6 fatty acids, 18:3n-3, and ratios of n-6 to n-3 fatty acids in the flesh lipids were directly related to the dietary level of CO and PF whereas 22:6n-3, the total of 20:5n-3 (eicosapentaenoic acid; EPA) and 22:6n-3 (docosahexaenoic acid; DHA), and n-3 fatty acids revealed the opposite trend. Percentages of 22:6n-3, EPA and DHA, and n-3 fatty acids were significantly depressed in fish fed diet COPF-60 versus diet COPF-0. We conclude that a 1:1 blend of CO and PF is an excellent cost-effective dietary source of supplemental lipid for Atlantic salmon in sea water.