Discrepancies in energy and macronutrient intakes between tests are apparent even when a solid prepackaged diet (Sdiet) is used to standardize dietary intake for preexperimental trials. It is unknown whether a liquid prepackaged diet (Ldiet) leads to improved adherence, resulting in lower variability in energy and macronutrient intakes. This study assesses the ability of athletes to replicate a diet when an Ldiet or Sdiet was used as a dietary standardization technique. In a cross-over design, 30 athletes were randomly assigned to either Sdiet or Ldiet. Each diet was consumed for two nonconsecutive days. Participants were instructed to consume all the meals provided and to return any leftovers. The coefficient of variation (CV) was calculated for each nutrient for the two methods and reported as the average CV. The Bland–Altman plots show that differences between Days 1 and 2 in energy and macronutrient intakes for both diets were close to zero, with the exception of some outliers. The %CV for Sdiet was higher than Ldiet (5% and 3% for energy, 5% and 3% for carbohydrate, 5% and 2% for protein, and 5% and 3% for fat, respectively). There was a strong positive correlation for energy and all macronutrients between Days 1 and 2 for both methods (r > .80; p < .05). Ldiet is an effective technique to standardize diet preexperimental trials and could be used as an alternative to Sdiet. Furthermore, Ldiet may lead to additional improvements in the compliance of participants to the diet and also decrease the cost and time of preparation.
Alaaddine El-Chab, Charlie Simpson and Helen Lightowler
Alaaddine El-Chab and Miriam E. Clegg
The effect of light- to moderate-intensity exercise, such as that used as a mode of transport, on glycemic response testing is unclear. The aim was to investigate the effect of acute exercise (walking and cycling), simulated to act as a mode of transport, prior to glycemic response testing on the intraindividual variability of blood glucose and insulin. A total of 11 male participants visited the laboratory four times. Initially, they undertook a maximum oxygen uptake and two submaximal exercise tests. For the other three visits, they either rested (25 min), cycled, or walked 5 km followed by a 2-hr glycemic response test after consuming a glucose drink (50 g of available carbohydrate). The mean coefficient of variation of each transport group was below the International Organization for Standardization cutoff of 30%. The highest mean coefficient of variation of glucose area under the curve (AUC) was between the rest and the walking trials (30%) followed by walking and cycling (26%). For insulin AUC, the highest mean coefficient of variation was between walking and cycling (28%) followed by rest and walking (24%). The lowest glucose AUC and insulin AUC were between rest and cycling (25% and 14%, respectively). This study did not find differences (p > .05) between the conditions for glucose AUC (at 120 min, rest: 134.5 ± 104.6 mmol/L; walking: 115.5 ± 71.7 mmol/L; and cycling: 142.5 ± 75 mmol/L) and insulin AUC (at 120 min, rest: 19.45 ± 9.12 μmol/ml; walking: 16.49 ± 8.42 μmol/ml; and cycling: 18.55 ± 9.23 μmol/ml). The results indicate no difference between the tests undertaken; however, further research should ensure the inclusion of two rest conditions.