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.

Continuous Glucose Monitoring (CGM) in Sports-A Comparison between a CGM Device and Lab-Based Glucose Analyser under Resting and Exercising Conditions in Athletes.

The objective of this pilot study was to compare glucose concentrations in capillary blood (CB) samples analysed in a laboratory by a validated method and glucose concentrations measured in the interstitial fluid (ISF) by continuous glucose monitoring (CGM) under different physical activity levels in a postprandial state in healthy athletes without diabetes. As a physiological shift occurs between glucose concentration from the CB into the ISF, the applicability of CGM in sports, especially during exercise, as well as the comparability of CB and ISF data necessitate an in-depth assessment. Ten subjects (26 ± 4 years, 67 ± 11 kg bodyweight (BW), 11 ± 3 h) were included in the study. Within 14 days, they underwent six tests consisting of (a) two tests resting fasted (HC_Rest/Fast and LC_Rest/Fast), (b) two tests resting with intake of 1 g glucose/kg BW (HC_Rest/Glc and LC_Rest/Glc), (c) running for 60 min at moderate (ModExerc/Glc), and (d) high intensity after intake of 1 g glucose/kg BW (IntExerc/Glc). Data were collected in the morning, following a standardised dinner before test day. Sensor-based glucose concentrations were compared to those determined from capillary blood samples collected at the time of sensor-based analyses and subjected to laboratory glucose measurements. Pearson's r correlation coefficient was highest for Rest/Glc (0.92, p < 0.001) compared to Rest/Fast (0.45, p < 0.001), ModExerc/Glc (0.60, p < 0.001) and IntExerc/Glc (0.70, p < 0.001). Mean absolute relative deviation (MARD) and standard deviation (SD) was smallest for resting fasted and similar between all other conditions (Rest/Fast: 8 ± 6%, Rest/Glc: 17 ± 12%, ModExerc/Glc: 22 ± 24%, IntExerc/Glc: 18 ± 17%). However, Bland-Altman plot analysis showed a higher range between lower and upper limits of agreement (95% confidence interval) of paired data under exercising compared to resting conditions. Under resting fasted conditions, both methods produce similar outcomes. Under resting postprandial and exercising conditions, respectively, there are differences between both methods. Based on the results of this study, the application of CGM in healthy athletes is not recommended without concomitant nutritional or medical advice.

Three Weeks of Detraining Does Not Decrease Muscle Thickness, Strength or Sport Performance in Adolescent Athletes.

The purpose of this study was to examine the effects of detraining following a block (BLOCK) or daily undulating periodized (DUP) resistance training (RT) on hypertrophy, strength, and athletic performance in adolescent athletes. Twenty-one males (age = 16 ± 0.7 years; range 15-18 years) were randomly assigned to one of two 12-week intervention groups (three full-body RT sessions per week): BLOCK (n = 9); DUP (n = 12). Subsequently a three-week detraining period was applied. Body mass, fat mass (FM), fat-free mass (FFM), muscle mass, muscle thickness (rectus femoris, vastus lateralis and triceps brachii), one-repetition maximum squat and bench press, countermovement jump (CMJ), peak power calculated from CMJ (Ppeak), medicine ball put distance, and 36.58m sprint were recorded before and after RT as well as after detraining. BLOCK and DUP were equally effective for improvements of athletic performance in young athletes. Both groups displayed significantly (ρ ≤ 0.05) higher values of all measures after RT except FM, which was unchanged. Only FM increased (p = 0.010; ES = 0.14) and FFM decreased (p = 0.018; ES = -0.18) after detraining. All other measurements were unaffected by the complete cessation of training. Values were still elevated compared to pre-training. Linear regression showed a strong correlation between the percentage change by resistance training and the decrease during detraining for CMJ (R2 = 0.472) and MBP (R2 = 0.629). BLOCK and DUP RT seem to be equally effective in adolescent athletes for increasing strength, muscle mass, and sport performance. In addition, three weeks of detraining did not affect muscle thickness, strength, or sport performance in adolescent athletes independent of previous resistance training periodization model used.