Evaluation of Validity and Reliability of a German General and Sports Nutrition Knowledge Questionnaire for Athletes and Coaches (GSNKQ-AC)

Despite the availability of nutritional recommendations, studies have reported inadequate nutrition in athletes. The existing literature highlights the importance of the nutritional knowledge of both athletes and coaches in influencing athletes’ food choices and behavior, as well as its direct and indirect impact on athletes’ performance and health. To adequately assess nutritional knowledge, monitoring via valid and reliable questionnaires is required. As no questionnaire tailored to German-speaking athletes and coaches exists, this study aimed at developing a new General and Sports Nutritional Knowledge Questionnaire for Athletes and Coaches (GSNKQ-AC). The development followed a literature-based, ten-step validation approach. The initial questionnaire (63 items) was revised and reduced to 29 items in the final version after conducting construct verification in the target group (n = 84 athletes and coaches), evaluating content validity by a panel of nutrition experts (n = 8), verifying face validity by think-out-loud interviews in the target group (n = 7), and conducting classical test theory for item reduction analysis (n = 53). For the final GSNKQ-AC, internal consistency, calculated as Cronbach’s alpha, was 0.87. Students with a focus on sports nutrition (n = 31) scored significantly higher than athletes and coaches (n = 53), revealing good construct validity (77% vs. 62%, p < 0.001). Test–retest reliability (n = 42, matched pairs) showed a Spearman’s correlation coefficient of r = 0.61 (p < 0.01). The brief GSNKQ-AC can be used for status quo or longitudinal assessment of nutritional knowledge among athletes and coaches to reveal gaps and ensure purposeful planning of educational interventions.