Discussion
METABOLIC DISEASES, RECRUITMENT, LITTLE
The main finding from this study was that an 11-min BWE protocol did not alter 24 h glycemic responses determined by CGM in young, healthy, inactive adults. In contrast to our hypothesis, we found no differences in 24 h mean glucose or indices of glycemic variability or postprandial glycemic responses after the BWE session as compared to a non-exercise CON condition. It is unclear whether the lack of effect was because the exercise stimulus was insufficient to alter glycemic responses in our cohort of relatively young healthy participants. It is possible that the glucose control of these individuals was already robust with relatively limited potential to be enhanced by an acute session of exercise like that used in our study. It is also possible that the timing of exercise relative to the meals or glucose drink ingestion may have influenced the results. This study nonetheless demonstrates the feasibility of performing BWE remotely while simultaneously utilizing CGM in a free-living situation.Little et alTwo previous studiesThe lack of change in glycemic control postexercise may also be related to the nutritional state of participants. Previous researchFrom a mechanistic standpoint, vigorous exercise elicits a variety of physiological responses that could influence indices of glycemic control postexercise. During an exercise session and for ~ 2 h postexercise, glucose supply to the skeletal muscle cells is elevated and there is also an enhanced capacity to uptake glucose into contracting skeletal muscleFuture studies are needed to further explore the effects of BWE on glycemic control in healthy individuals and in individuals with impaired glucose control. For example, studies exploring larger doses of acute BWE to help determine the minimum exercise prescription required to see an effect in this population would be warranted. Additionally, investigating the effects of repeated bouts of BWE in the form of training studies would be useful to explore the potential for chronic exercise to alter glycemic control. Also, studying the effects of various nutritional manipulations surrounding BWE interventions would be helpful. For example, investigating how glycemic control is influenced by fasted vs fed state exercise, the timing of meals surrounding exercise, as well as the glycemic indices of foods consumed. Our study was powered to detect changes in our primary outcome of 24 h mean glucose, therefore future adequately powered studies should further probe the impact of BWE on glycemic variability given the fact that our MAGE data trended towards showing a benefit from BWE although this was not statistically significant (p = 0.06). Additionally, future work should explore whether there are sex-based differences in glycemic responses to BWE. Also, studies investigating the mechanistic basis behind observed increases, decreases, or no changes seen in glycemic control following exercise would be warranted. Further, including measures of counter-regulatory hormone responses (i.e., insulin action) in future work would be valuable since it is possible that acute exercise protocols could alter insulin concentrations without an observed change in glucose. Such studies should be conducted in a variety of study populations such as healthy adults, individuals with impaired glucose control, or those at risk of developing metabolic diseases. Perhaps other study populations would be more sensitive to the effects of BWE on glycemic control compared to the young, healthy adults we recruited.Some strengths of the present study included the level of nutritional control, the use of CGM in a free-living situation, the recruitment of both sexes, as well as the menstrual cycle control implemented with the female participants. Whereas some limitations of the design included the use of self-reported dietary logs, conducting remote visits which created less environmental or laboratory-based control, as well as the lack of counterbalancing the number of males and females. We provided participants with controlled, pre-packaged meals to consume during the 24 h CGM measurement period. This was a strength of the study design because it allowed for an enhanced level of nutritional control within each participant, ensuring that they consumed the same meals on both trials. Meal and beverage consumption patterns (i.e., timing and amount consumed) were self-reported by the participants in a meal and beverage log. This could be considered a limitation of the study given the potential difficulties surrounding self-reported data. We utilized CGM which is considered a very detailed and sensitive measurement tool that produces comprehensive glucose data. This study was designed to simulate a practical, free-living situation where the intervention was completed remotely at-home and the use of CGM facilitated this design due to the fact that participants did not have to be in the lab for the collection of glucose data. Although conducting a free-living study comes with its own benefits it also removes aspects of lab-based studies which have a superior level of environmental and activity control. For example, the free-living nature of this study resulted in the activity levels of our participants not being standardized in the 2 h following the consumption of the 75 g glucose drink which could be considered a limitation. A strength of our study was the unbiased recruitment of both males and females. We also controlled for menstrual cycle in our female participants to ensure that hormonal profiles were similar during both trials. However, we did not counterbalance for sex in our recruitment and therefore, we ended up with more females than males (n = 19 vs n = 8 respectively). This limitation may be particularly relevant since Gillen et al