Publications

2025

1. 

   Increased Postprandial Metabolic flexibility is Associated with Higher Body Fat Percentages in Healthy Young Adults

   Nicholas A. Foreman, Sahil Rajwade, Jaiden Bluth, and 5 more authors

   American Journal of Physiology-Endocrinology and Metabolism, Dec 2025

   Abs DOI

   Because higher adiposity is associated with cardiometabolic disease, we assessed the relationship between body composition (body fat percentage; BF%) and postprandial metabolic flexibility [change in respiratory exchange ratio (RER) from fasting]. Young adults [ n = 27, n = 15 females, body mass index (BMI) = 27.1 ± 4.5; BF% = 30.4 ± 8.7; mean ± SD] without overt pathology completed a 100 g oral glucose tolerance test (OGTT). Indirect calorimetry before (fasting) and following (30, 60, 90, and 120 min) consumption was used to calculate respiratory exchange ratio (RER) and oxidation of carbohydrates (CHOX) and fats (FOX). Serum and plasma were collected at corresponding time points and analyzed for glucose, insulin, and nonesterified fatty acids (NEFAs). Two-way repeated measures ANOVA was used to compare data between normal weight and overweight/obesity by BMI. The effect of BF% on postprandial metabolic flexibility was tested via linear mixed models while adjusting for potential confounders. During the OGTT, blood glucose, serum insulin, plasma lactate, RER, and CHOX all significantly increased, whereas plasma NEFAs and whole body FOX decreased (all P < 0.05). BF% modified the relationship between postprandial RER and time ( P = 0.019); individuals with higher BF% increase their RER faster and to a greater extent (i.e., greater metabolic flexibility) than those with lower BF%. Body fat percentage is associated with greater postprandial metabolic flexibility during an OGTT in young adults. Despite increased adiposity, metabolic flexibility may be preserved, representing a compensatory adaptation to decreased glucose storage in the postprandial period. NEW & NOTEWORTHY Previous studies have suggested that obesity blunts postprandial metabolic flexibility. By directly analyzing the effect of body composition on postprandial metabolic flexibility, we show that healthy young adults with higher body fat percentages have increased postprandial metabolic flexibility in response to concurrent hyperglycemia. This suggests a preserved, metabolically flexible phenotype in young adults with higher body fat percentages.

2022

1. Practices and Applications of Heart Rate Variability Monitoring in Endurance Athletes

   Christopher J Lundstrom, Nicholas A Foreman, and George Biltz

   International Journal of Sports Medicine, Jul 2022

   DOI

2. 

   Assessment of a Treadmill Speed Incline Conversion Chart: A Validation Study

   Nicholas A. Foreman, Emma J. Lee, and Christopher J. Lundstrom

   International Journal of Sports Physiology and Performance, Mar 2022

   Abs DOI

   Purpose: To investigate the validity of a treadmill speed incline conversion chart using physiological and subjective measures. Methods: Two groups of experienced runners (SLOW and FAST: divided based on their easy run pace) ran 6 speed incline combinations for 5 minutes each. Stages were equivalent according to the HillRunner.com chart, and stage order was randomized. Due to limitations of the chart, SLOW (n = 11) ran at inclines up to 4%, while FAST (n = 22) ran at inclines up 10%. Oxygen consumption (VO2), respiratory exchange ratio, heart rate, blood lactate, overall rating of perceived exertion (RPE), and leg RPE were measured for each stage. VO2 was compared against the VO2 predicted by the American College of Sports Medicine (ACSM) equation (ACSM VO2). Repeated-measures analysis of variance was used to detect differences between stages and inclines, and Hedges g was used as a measure of effect size. Results: Pooled results (0%-4%, N = 33) showed no incline effect on VO2, respiratory exchange ratio, heart rate, blood lactate, or RPE (P > .05; ηp2=.198), validating the chart at these inclines. At or above 6%, meaningful and significant increases occur in VO2 (g > 0.9, P < .05), with increases in heart rate, blood lactate, and leg RPE at higher inclines. ACSM VO2 underestimated oxygen consumption at all inclines up to 8% (P < .05) but not at 10% (45.9 [4.0] vs 46.7 [2.4] mL·kg-1·min-1; P = .186). Conclusion: The HillRunner.com chart is only valid at or below 4%. At higher inclines, supposedly equivalent stages result in increased exercise intensity. ACSM VO2 underestimates VO2 in trained runners at inclines up to 8%.

2021

1. Redox signaling and sarcopenia: searching for the primary suspect

   Nicholas A Foreman, Anton S Hesse, and Li Li Ji

   International journal of molecular sciences, Aug 2021

   DOI