Effect of a marathon run on serum lipoproteins, creatine kinase, and lactate dehydrogenase in recreational runners

The objective of this study was to determine the effect of a marathon run on serum lipid and lipoprotein concentrations and serum muscle enzyme activities and follow their recovery after the run. These blood concentrations were measured before, immediately after, and serially after a marathon run in 15 male recreational runners. The triglyceride level was significantly elevated postrace, then fell 30% below baseline 1 day after the run, and returned to baseline after 1 week. Total cholesterol responded less dramatically but with a similar pattern. High-density lipoprotein cholesterol remained significantly elevated and low-density lipoprotein cholesterol was transiently reduced for 3 days after the run. The total cholesterol/high-density cholesterol ratio was significantly lowered for 3 days. Serum lactate dehydrogenase activity significantly doubled postrace and then declined but remained elevated for 2 weeks. Serum creatine kinase activity peaked 24 hr after the run, with a 15-fold rise, and returned to baseline after 1 week. The rise of these enzymes reflects mechanically damaged muscle cells leaking contents into the interstitial fluid. It is concluded that a prolonged strenuous exercise bout in recreational runners, such as a marathon, produces beneficial changes in lipid blood profiles that are significant for only 3 days. However, muscle damage is also evident for 1 week or more from the dramatic and long-lasting effect on enzyme levels. Laboratory values for these runners were outside normal ranges for some days after the race.     

Interpreting WISC-R and McCarthy scatter: A caution

In this investigation, indices of scatter on the WISC-R and McCarthy Scales were examined for 20 educable mentally retarded and 20 learning disabled children in relation to a similar control group. The scatter found in the two exceptional samples was also compared to the variability found in the standardization samples of the WISC-R and McCarthy. Results indicated that the learning-disabled sample exhibited more WISC-R subtest scatter and McCarthy Scale variability than the standardization sample but not more than the control group. The implications of these findings are discussed.     

How can we know a self-driving car is safe?

Self-driving cars promise solutions to some of the hazards of human driving but there are important questions about the safety of these new technologies. This paper takes a qualitative social science approach to the question ‘how safe is safe enough?’ Drawing on 50 interviews with people developing and researching self-driving cars, I describe two dominant narratives of safety. The first, safety-in-numbers, sees safety as a self-evident property of the technology and offers metrics in an attempt to reassure the public. The second approach, safety-by-design, starts with the challenge of safety assurance and sees the technology as intrinsically problematic. The first approach is concerned only with performance—what a self-driving system does. The second is also concerned with why systems do what they do and how they should be tested. Using insights from workshops with members of the public, I introduce a further concern that will define trustworthy self-driving cars: the intended and perceived purposes of a system. Engineers’ safety assurances will have their credibility tested in public. ‘How safe is safe enough?’ prompts further questions: ‘safe enough for what?’ and ‘safe enough for whom?’

     

BMI-referenced cut-points for recommended daily pedometer-determined steps in Australian children and adolescents

The purpose of this study was to establish sex-specific criterion-referenced standards for pedometer-determined physical activity related to body mass index (BMI)-defined weight status among youth. We analyzed data from 7-16-year-old boys (n = 338) and girls (n = 337) and used pedometer-assessed physical activity and anthropometric data to derive average steps/day and BMI. Sex-specific criterion-referenced standards for steps/day relating to healthy weight and overweight/obese were determined using the contrasting groups method. Healthy weight children took more steps/day than overweight or obese (boys: 14,413 vs. 12,088, and girls: 12,562 vs. 10,114, respectively; p < .001). The optimal BMI-referenced cut-point emerging flom our sample was 16,000 steps/day for both boys and girls. Our results and those reported elsewhere suggest that youth take insufficient pedometer-determined steps/day to avoid becoming overweight.     

Self-presentation origins of choking: evidence from separate pressure manipulations

Whether self-presentation is involved in the choking process remains unknown. The purpose of the current study was to determine the role of self-presentation concerns on the frequency of choking within the context of a recently proposed self-presentation model. Experienced field hockey players (N = 45) were randomly assigned to one of five groups (i.e., performance-contingent monetary incentive, video camera placebo, video camera self-presentation, audience, or combined pressure), before taking penalty strokes in low- and high-pressure phases. Results indicated that groups exposed to self-presentation manipulations experienced choking, whereas those receiving motivational pressure treatments decreased anxiety and increased performance under pressure. Furthermore, cognitive state anxiety mediated the relationship between the self-presentation group and performance. These findings provide quantitative support for the proposed self-presentation model of choking, while also holding implications for anxiety manipulations in future sport psychology research.