The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes

Carbohydrate (CHO) availability could alter mucosal immune responses to exercise. This study compared the effect of three dietary approaches to CHO availability on resting and post-exercise s-IgA levels. Elite race walkers (n = 26) adhered to a high CHO diet (HCHO), periodised CHO availability (PCHO) or a low CHO/high fat diet (LCHF) for 3 weeks while completing an intensified training program. HCHO and PCHO groups consumed 8.0–8.5 g.kg^?1 CHO daily, with timing of ingestion manipulated to alter CHO availability around key training sessions. The LCHF diet comprised 80% fat and restricted CHO to < 50 g.day^?1. A race walk test protocol (19 km females, 25 km males) was completed at baseline, after adaptation, and following CHO restoration. On each occasion, saliva samples were obtained pre- and post-exercise to quantify s-IgA levels. Resting s-IgA secretion rate substantially increased ~ two-fold post-intervention in all groups (HCHO: 2.2 ± 2.2, PCHO: 2.8 ± 3.2, LCHF: 1.6 ± 1.6; fold-change± 95% confidence limits), however, no substantial differences between dietary treatments were evident. Post-exercise, substantial 20–130% increases in s-IgA concentration and 43–64% reductions in flow rate occurred in all dietary treatments, with trivial differences evident between groups. It appears that high volume training overrides any effect of manipulating CHO availability on mucosal immunity in elite athletes.     

Randomized interdependent group contingencies: Group reinforcement with a twist

This investigation examined the effects of randomizing components of an interdependent group contingency procedure on the target behavior of 12 students in a second‐grade classroom in a rural southeastern school district. Specifically, using a multiphase time‐series design (i.e., A‐B‐A‐C‐B‐C design) levels of disruptive behavior were compared across baseline, an intervention phase with only randomized reinforcers (the RR+ phase), and an intervention phase with all components randomized (R‐ALL phase). Results suggest that both interventions were successful in decreasing levels of disruptive behavior, with the R‐ALL phase resulting in lower mean, and more stable, percentages of disruptive behavior. The advantages to randomizing components within a group contingency procedure are discussed, because this procedure not only incorporates the strengths of an interdependent group contingency, but also addresses the limitations. © 2000 John Wiley & Sons, Inc.     

Effect on development of proportional reasoning skill of physical experience and cognitive abilities associated with prefrontal lobe activity

The present study tested the hypothesis that maturing prefrontal lobes play a role in the development of proportional reasoning skill because the prefrontal lobes are involved in the inhibition of task‐irrelevant information and the representation of task‐relevant information. The hypothesis that reasoning development is in part dependent upon physical experience was also tested. Students (all males) who failed to solve a diagnostic proportions task were administered several tests of prefrontal lobe functions. The students were then randomly assigned to manipulative or verbal tutoring groups. Both groups received a series of individual testing, tutoring and testing sessions on proportional reasoning. As predicted, performance on the prefrontal lobe tasks (measures of inhibiting ability, planning ability, dissembedding ability, and working memory capacity) significantly predicted performance on proportional reasoning tasks following tutoring. Students' computational skills were not a significant predictor. Also, the manipulative group's proportional reasoning performance was significantly higher than that of the verbal tutoring group. Therefore, the present results provide support for the hypothesis that maturing prefrontal lobes and physical experience play roles in the development of proportional reasoning skill. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 1171–1182, 2000     

Development of Scientific Reasoning in College Biology: Do Two Levels of General Hypothesis‐Testing Skills Exist?

The primary purpose of the present study was to test the hypothesis that two general developmentally based levels of hypothesis‐testing skills exist. The first hypothesized level presumably involves skills associated with testing hypotheses about observable causal agents; the second presumably involves skills associated with testing hypotheses involving unobservable entities. To test this hypothesis, a hypothesis‐testing skills test was developed and administered to a large sample of college students both at the start and at the end of a biology course in which several hypotheses at each level were generated and tested. The predicted positive relationship between level of hypothesis‐testing skill and performance on a transfer problem involving the test of a hypothesis involving unobservable entities was found. The predicted positive relationship between level of hypothesis‐testing skill and course performance was also found. Both theoretical and practical implications of the findings are discussed. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 81–101, 2000     

Influence of a Reflective Explicit Activity‐Based Approach on Elementary Teachers' Conceptions of Nature of Science

This study assessed the influence of a reflective, explicit, activity‐based approach to nature of science (NOS) instruction undertaken in the context of an elementary science methods course on preservice teachers' views of some aspects of NOS. These aspects included the empirical, tentative, subjective (theory‐laden), imaginative and creative, and social and cultural NOS. Two additional aspects were the distinction between observation and inference, and the functions of and relationship between scientific theories and laws. Participants were 25 undergraduate and 25 graduate preservice elementary teachers enrolled in two sections of the investigated course. An open‐ended NOS questionnaire coupled with individual interviews was used to assess participants' NOS views before and at the conclusion of the course. The majority of participants held naive views of the target NOS aspects at the beginning of the study. During the first week of class, participants were engaged in specially designed activities that were coupled with explicit NOS instruction. Throughout the remainder of the course, participants were provided with structured opportunities to reflect on their views of the target NOS aspects. Postinstruction assessments indicated that participants made substantial gains in their views of some of the target NOS aspects. Less substantial gains were evident in the case of the subjective, and social and cultural NOS. The results of the present study support the effectiveness of explicit, reflective NOS instruction. Such instruction, nonetheless, might be rendered more effective when integrated within a conceptual change approach. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 295–317, 2000.     

Physiological responses to 1000-m ergometer time-trial performance in outrigger canoeing

Graded exercise tests are commonly used to assess peak physiological capacities of athletes. However, unlike time trials, these tests do not provide performance information. The aim of this study was to examine the peak physiological responses of female outrigger canoeists to a 1000-m ergometer time trial and compare the time-trial performance to two graded exercise tests performed at increments of 7.5 W each minute and 15 W each two minutes respectively. 17 trained female outrigger canoeists completed the time trial on an outrigger canoe ergometer with heart rate (HR), stroke rate, power output, and oxygen consumption (VO2) determined every 15 s. The mean (+/- s) time-trial time was 359 +/- 33 s, with a mean power output of 65 +/- 16 W and mean stroke rate of 56 +/- 4 strokes min(-1). Mean values for peak VO2, peak heart rate, and mean heart rate were 3.17 +/- 0.67 litres min(-1), 177 +/- 11 beats min(-1), and 164 +/- 12 beats min(-1) respectively. Compared with the graded exercise tests, the time-trial elicited similar values for peak heart rate, peak power output, peak blood lactate concentration, and peak VO2. As a time trial is sport-specific and can simultaneously quantify sprint performance and peak physiological responses in outrigger canoeing, it is suggested that a time trial be used by coaches for crew selection as it doubles as a reliable performance measure and a protocol for monitoring peak aerobic capacity of female outrigger canoeists.