News & Views from the Editor-in-Chief - L. Bruce Gladden
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Our journal continues to publish notable research studies, and I am highlighting three stand-outs this month. First, evidence is accumulating that prolonged sitting can be detrimental. Rafiei and colleagues aimed to determine if exercise “snacks" could protect against some of these negative impacts. Young healthy individuals and adults with obesity completed two trials involving either 9 h sitting or a “stair snacks" condition during which they interrupted sitting by climbing three flights of stairs once per hour (ascending as quickly and safely as possible). Standardized meals were consumed at 0, 3, and 6 h with blood samples taken every 30 min. Glucose area under the curve (AUC) was not different between the conditions but insulin and free fatty acid AUCs were lower in the stair snacks condition in the participants with obesity. This indicates that insulin sensitivity among the obese participants was likely improved when prolonged sitting was interrupted with as little as 15–30 s of stair climbing exercise per hour.
Second, cardiorespiratory fitness (CRF) is a clinical vital sign that should be regularly assessed. Different assessment procedures are available, including estimating CRF from submaximal and maximal exercise tests. The study by Peterman and coworkers used data from the Ball State Adult Fitness Longitudinal Lifestyle Study (BALL ST) cohort. They compared the accuracy of commonly used exercise-based CRF prediction equations with directly measured CRF via cardiopulmonary gas analysis. Although the exercise-based prediction equations were correlated with directly measured CRF, the equations had a low degree of accuracy in categorizing participants into CRF classifications related to the risk of morbidity or mortality. These findings support recommendations to increase use of maximal exercise tests with direct cardiopulmonary measures to accurately assess CRF within a clinical setting.
Finally, Chu and colleagues used noninvasive 13C-glucose stable isotope methodology to show that metabolic flexibility (MetFlex) during exercise was impaired by 23.5% in children with obesity compared to matched controls. Reduced MetFlex could be associated with lower carbohydrate uptake via non-insulin mediated mechanisms (e.g., skeletal muscle contraction), although this is difficult to confirm without muscle biopsies. The authors also reported lower MetFlex at rest in children with obesity, suggesting that endocrine-related compensatory mechanisms for insulin resistance (e.g., hyperinsulinemia) failed to fully restore carbohydrate in skeletal muscle preexercise. Additional research is warranted to fully elucidate the mechanisms involved. Notably, the key findings showed obesity at a young age affects the ability to match substrate availability with substrate utilization, independent of age, sex, and pubertal stage.
L. Bruce Gladden
School of Kinesiology
Auburn University
