Social cognitive theory and the theories of reasoned action and planned behavior were examined in the prediction of 4 weeks of physical activity participation. The theories of reasoned action and planned behavior were supported. Attitude and perceived control predicted intention, and intention predicted physical activity participation. The social cognitive theory variables significantly predicted physical activity participation, with self-efficacy and self-evaluation of the behavior significantly contributing to the prediction. The greater the confidence in participating in physical activity and the greater the satisfaction with present physical activity, the more physical activity performed. Hierarchical regression analyses indicated that perceived control and intentions did not account for any unique variation in physical activity participation over self-efficacy. Therefore the social cognitive theory constructs were better predictors of physical activity than those from the theories of reasoned action and planned behavior.
David A. Dzewaltowski, John M. Noble and Jeff M. Shaw
Jeff M. Shaw, David A. Dzewaltowski and Mary McElroy
Self-efficacy and causal attributions were examined as mediators of perceived psychological momentum. Participants were randomly assigned to either a repeated success or a repeated failure group in which success or failure was manipulated by having participants compete against a highly skilled confederate. Each participant and confederate performed three sets of 10 basketball free throws. Free throw self-efficacy, perceived psychological momentum, and causal dimensions were assessed after each set. Results indicated that the success and failure manipulations were effective in that the responses changed differently over time for both groups. Experiencing competitive success increased perceptions of momentum; experiencing competitive failure decreased perceptions of momentum. In contrast, self-efficacy only changed in response to competitive success as the participants became more confident. Both groups attributed the competitive outcome to internal, personally controllable, and unstable causes.
Gregory Shaw, Anu Koivisto, David Gerrard and Louise M. Burke
Open-water swimming (OWS) is a rapidly developing discipline. Events of 5–25 km are featured at FINA World Championships, and the international circuit includes races of 5–88 km. The Olympic OWS event, introduced in 2008, is contested over 10 km. Differing venues present changing environmental conditions, including water and ambient temperatures, humidity, solar radiation, and unpredictable tides. Furthermore, the duration of most OWS events (1–6 hr) creates unique physiological challenges to thermoregulation, hydration status, and muscle fuel stores. Current nutrition recommendations for open-water training and competition are either an extension of recommendations from pool swimming or are extrapolated from other athletic populations with similar physiological requirements. Competition nutrition should focus on optimizing prerace hydration and glycogen stores. Although swimmers should rely on self-supplied fuel and fluid sources for shorter events, for races of 10 km or greater, fluid and fuel replacement can occur from feeding pontoons when tactically appropriate. Over the longer races, feeding pontoons should be used to achieve desirable targets of up to 90 g/hr of carbohydrates from multitransportable sources. Exposure to variable water and ambient temperatures will play a significant role in determining race nutrition strategies. For example, in extreme environments, thermoregulation may be assisted by manipulating the temperature of the ingested fluids. Swimmers are encouraged to work with nutrition experts to develop effective and efficient strategies that enhance performance through appropriate in-competition nutrition.
David M. Shaw, Fabrice Merien, Andrea Braakhuis, Daniel Plews, Paul Laursen and Deborah K. Dulson
This study investigated the effect of the racemic β-hydroxybutyrate (βHB) precursor, R,S-1,3-butanediol (BD), on time-trial (TT) performance and tolerability. A repeated-measures, randomized, crossover study was conducted in nine trained male cyclists (age, 26.7 ± 5.2 years; body mass, 69.6 ± 8.4 kg; height, 1.82 ± 0.09 m; body mass index, 21.2 ± 1.5 kg/m2; VO2peak,63.9 ± 2.5 ml·kg−1·min−1; W max, 389.3 ± 50.4 W). Participants ingested 0.35 g/kg of BD or placebo 30 min before and 60 min during 85 min of steady-state exercise, which preceded a ∼25- to 35-min TT (i.e., 7 kJ/kg). The ingestion of BD increased blood D-βHB concentration throughout exercise (0.44–0.79 mmol/L) compared with placebo (0.11–0.16 mmol/L; all p < .001), which peaked 1 hr following the TT (1.38 ± 0.35 vs. 0.34 ± 0.24 mmol/L; p < .001). Serum glucose and blood lactate concentrations were not different between trials (all p > .05). BD ingestion increased oxygen consumption and carbon dioxide production after 20 min of steady-state exercise (p = .002 and p = .032, respectively); however, no further effects on cardiorespiratory parameters were observed. Within the BD trial, moderate to severe gastrointestinal symptoms were reported in five participants, and low levels of dizziness, nausea, and euphoria were reported in two participants. However, this had no effect on TT duration (placebo, 28.5 ± 3.6 min; BD, 28.7 ± 3.2 min; p = .62) and average power output (placebo, 290.1 ± 53.7 W; BD, 286.4 ± 45.9 W; p = .50). These results suggest that BD has no benefit for endurance performance.