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Timothy D. Heden, Ying Liu, Young-Min Park, Nathan C. Winn and Jill A. Kanaley

Background:

This study assessed if walking at a self-selected pace could improve postprandial glucose and insulin concentrations in obese adolescents consuming high-fructose (HF) or high-glucose (HG) diets.

Methods:

Seven obese male and female adolescents (18 ± 1 yr) performed 4, 15-day trials in a random order, including 1) HF-diet (50 g fructose/d added to normal diet) while being sedentary, 2) HG-diet (50 g glucose/d) while sedentary, 3) HF-diet with additional walking, and 4) HG-diet with additional walking. On the 15th day of each trial, the participants performed mixed meal testing in the laboratory in which they consumed three liquid shakes (either HF or HG) and during the HF and HG sedentary trials, the participants took < 4000 steps while in the laboratory but during the walking trials took ≥ 13,000 steps during testing.

Results:

Walking did not alter postprandial glucose concentrations. Although walking reduced insulin secretion by 34% and 25% during the HF- and HG-diet, respectively (P < .05), total insulin concentrations were only significantly reduced (P > .05) with walking during the HF trial, possibly because walking enhanced insulin clearance to a greater extent during the HF-diet.

Conclusions:

Walking reduces postprandial insulin secretion in obese adolescents consuming a high-fructose or high-glucose diet.

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Laís Monteiro Rodrigues Loureiro, Caio Eduardo Gonçalves Reis and Teresa Helena Macedo da Costa

involved in the process of glycogen synthesis. Adenosine monophosphate-activated protein kinase (AMPK) is an enzyme responsible for the translocation of glucose transporter 4 (GLUT-4) to the cell membrane when activated by skeletal muscle contraction ( Mu et al., 2001 ; Stapleton et al., 1996 ). AMPK

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Rachel B. Parks, Hector F. Angus, Douglas S. King and Rick L. Sharp

synergistic actions of insulin and muscle contractions stimulated GLUT4 translocation until counterregulatory hormones normalized blood glucose by ∼30 min into exercise ( Defronzo et al., 1981 ; Hargreaves et al., 1987 ). However, subsequent studies could not replicate the results, instead finding

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Xiaomin Sun, Zhen-Bo Cao, Kumpei Tanisawa, Satomi Oshima and Mitsuru Higuchi

football ( Guo et al., 2013 ; Murata et al., 2016 ; Selden et al., 2009 ) athletes, who often intentionally try to increase their body mass as a means of performance enhancement. Selden et al. ( 2009 ) reported that players from the National Football League have higher fasting glucose concentrations

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Whitney A. Welch, Scott J. Strath, Michael Brondino, Renee Walker and Ann M. Swartz

health effects of sedentary behavior has been performed, research in adults has shown that breaks from sedentary behavior are beneficial for glucose regulation. 9 , 10 These proposed breaks are generally accomplished by introducing some type of LPA such as standing or slow walking; range in duration

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Mynor Rodriguez-Hernandez, Jeffrey S. Martin, David D. Pascoe, Michael D. Roberts and Danielle W. Wadsworth

behavior, 7 , 14 , 18 positively affect markers of cardiometabolic diseases, 6 – 8 , 19 , 20 reduce glucose and insulin responses, 7 , 17 reduce lipid concentrations, 1 and improve positive indicators of health such as glucose stability. 14 The growing evidence shows beneficial effects on health

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Susan Sullivan Glenney, Derrick Paul Brockemer, Andy C. Ng, Michael A. Smolewski, Vladimir M. Smolgovskiy and Adam S. Lepley

effects of exercise training on cardiovascular health. Traditional serum biomarkers, such as total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), glucose, C-reactive protein (CRP), insulin, and triglyceride levels, have been used to study the effects of exercise interventions

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Ilkka Heinonen, Jukka Kemppainen, Toshihiko Fujimoto, Juhani Knuuti and Kari K. Kalliokoski

metabolism of human bone marrow increases from a resting state to low-intensity exercise ( Heinonen et al., 2013a ). Furthermore, measurement of glucose uptake (GU) by 18 F-fluorodeoxyglucose (FDG) in mouse bone at rest demonstrated that relative to other tissues, bone accumulated a significant fraction of

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Erik A. Richter, Jørgen F.P. Wojtaszewski, Søren Kristiansen, Jens R. Daugaard, Jakob N. Nielsen, Wim Derave and Bente Kiens

In the present short review some factors affecting glucose utilization during exercise in skeletal muscle will be briefly described. Special focus will be put on the glucose transport step across the sarcolemma. Glucose transporters (GLUT4) are expressed at a surprisingly similar level in the different muscle fiber types in human skeletal muscle in contrast to findings in the rat. When working at the same absolute work load muscle glucose transport is decreased in trained compared with untrained muscle in part due to a decrease in GLUT4 translocation to the sarcolemma in trained muscle. However, when trained and untrained muscle are stressed severely by a workload taxing 100% of their peak oxygen uptake in a glycogen-depleted state, then glucose uptake is larger in trained than in untrained muscle and correlates with muscle GLUT4 content. Finally, the possible role of the AMP-activated protein kinase (AMPK) in regulating glucose uptake during exercise is discussed. It is indicated that at present no experiments definitively link activation of AMPK to activation of muscle glucose transport during exercise.

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Andrew R. Coggan, Robert J. Spina, Wendy M. Kohrt, Dennis M. Bier and John O. Holloszy

We hypothesized that when plasma glucose availability is maintained by carbohydrate (CHO) ingestion, trained cyclists can utilize plasma glucose at very high rates during the later stages of prolonged exercise (10). To test this hypothesis, a well-trained male cyclist was studied during exercise to fatigue at 70% VO2max when ingesting glucose throughout exercise. A primed continuous infusion of [U-13C]glucose was begun after 60 min of exercise to measure rates of plasma glucose appearance (Ra), disappearance (Rd), and oxidation (Rox). Ra and Rd rose progressively throughout exercise, peaking at 6.85 and 6.99 mmollmin, respectively, at fatigue (i.e., 133 min). Most (93%) of this glucose was oxidized; during the final 30 min of exercise, Rox, averaged 6.10 mmollmin and accounted for approximately half of total CHO oxidation. These results support the hypothesis that trained cyclists can oxidize plasma glucose at very high rates during the later stages of prolonged exercise when fed CHO.