The assessment of dietary attitudes and behaviors provides information of interest to sports nutritionists. Although there has been little analysis of the quality of research undertaken in this field, there is evidence of a number of flaws and methodological concerns in some of the studies in the available literature. This review undertook a systematic assessment of the attributes of research assessing the nutritional knowledge and attitudes of athletes and coaches. Sixty questionnaire-based studies were identified by a search of official databases using specific key terms with subsequent analysis by certain inclusion–exclusion criteria. These studies were then analyzed using 33 research quality criteria related to the methods, questionnaires, and statistics used. We found that many studies did not provide information on critical issues such as research hypotheses (92%), the gaining of ethics approval (50%) or informed consent (35%), or acknowledgment of limitations in the implementation of studies or interpretation of data (72%). Many of the samples were nonprobabilistic (85%) and rather small (42%). Many questionnaires were of unknown origin (30%), validity (72%), and reliability (70%) and resulted in low (≤ 60%) response rates (38%). Pilot testing was not undertaken in 67% of the studies. Few studies dealt with sample size (2%), power (3%), assumptions (7%), confidence intervals (3%), or effect sizes (3%). Improving some of these problems and deficits may enhance future research in this field.
Rozalia Kouvelioti and George Vagenas
Panagiota Klentrou, Kirina Angrish, Nafisa Awadia, Nigel Kurgan, Rozalia Kouvelioti and Bareket Falk
Purpose: This study examined osteokines related to Wnt signaling at rest and in response to plyometric exercise in 12 boys [10.2 (0.4) y] and 12 girls [10.5 (0.4) y]. Methods: One resting (preexercise) and 3 postexercise (5 min, 1 h, and 24 h) blood samples were analyzed for sclerostin, dickkopf-related protein 1 (DKK-1), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-β ligand (RANKL). Results: Girls had higher resting sclerostin than boys [187.1 (40.1) vs 150.4 (36.4) pg·mL−1, respectively; P = .02]. However, boys had higher DKK-1 [427.7 (142.3) vs 292.8 (48.0) pg·mL−1, respectively; P = .02] and RANKL [3.9 (3.8) vs 1.0 (0.4) pg·mL−1, respectively; P < .01] than girls. In girls, sclerostin significantly decreased 5-minute and 1-hour postexercise (χ2 = 12.7, P = .01), and RANKL significantly decreased 5-minute postexercise (χ2 = 19.1, P < .01) and continued to decrease up to 24-hour postexercise, with large effect sizes. In boys, DKK-1 significantly decreased 1-hour postexercise and remained lower than preexercise 24-hour postexercise (χ2 = 13.0, P = .01). OPG increased in both boys (χ2 = 13.7, P < .01) and girls (χ2 = 11.4, P = .01), with boys having significantly higher OPG at 5-minute and 1-hour postexercise, whereas in girls, this increase was only seen 24-hour postexercise. Conclusion: Plyometric exercise induces an overall anabolic osteokine response favoring osteoblastogenesis over osteoclastogenesis in both boys and girls although the timeline and mechanism(s) may be different.