TY - JOUR
T1 - Repeated Prolonged Exercise Decreases Maximal Fat Oxidation in Older Men
AU - Morville, Thomas
AU - Rosenkilde, Mads
AU - Munch-Andersen, Thor
AU - Riis Andersen, Peter
AU - Groenbæk, Katja Kjær
AU - Helbo, Signe
AU - Kristensen, Marianne
AU - Vigelsø, Andreas
AU - Mattsson, Nick
AU - Kruuse Rasmusen, Hanne
AU - Guadalupe-Grau, Amelia
AU - Fago, Angela
AU - Neigaard Hansen, Christina
AU - Twelkmeyer, Brigitte
AU - Løvind Andersen, Jesper
AU - Dela, Flemming
AU - Wulff Helge, Jørn
PY - 2017/2
Y1 - 2017/2
N2 - INTRODUCTION/PURPOSE: Fat metabolism and muscle adaptation was investigated in 6 older trained men (age: 61 ± 4 years; VO2max: 48 ± 2 mL kg min) following repeated prolonged exercise).METHODS: 2706 km (1,681 miles) cycling was performed over 14 days and a blood sample and a muscle biopsy were obtained at rest after an overnight fast before and 30 hours after the completion of the cycling. VO2-max and maximal fat oxidation were measured using incremental exercise tests. Heart rate was continuously sampled during cycling to estimate exercise intensity.RESULTS: The daily duration of exercise was 10 hours and 31 ± 37 min and the mean intensity was 53 ± 1 % of VO2max. Body weight remained unchanged. VO2max and maximal fat oxidation rate decreased by 6 ± 2 % (P = 0.04) and 32 ± 8 % (P < 0.01), respectively. The exercise intensity that elicits maximal fat oxidation was not significantly decreased. Plasma free fatty acid (FA) concentration decreased (P < 0.002) from 500 ± 77 to 160 ± 38 μmol L. Plasma glucose concentration as well as muscle glycogen, myoglobin and triacylglycerol content remained unchanged. Muscle citrate synthase (CS)- and ß-hydroxy-Acyl-CoA-dehydrogenase (HAD)- activity were unchanged, but the protein expression of HKII, GLUT4 and ATGL were significantly increased.CONCLUSION: Overall the decreased maximal fat oxidation was probably due to lower exogenous plasma FA availability and the muscle adaptation pattern indicates an increased glucose transport capacity and an increased muscle lipolysis capacity supporting an increased contribution of exogenous glucose and endogenous fat during exercise.
AB - INTRODUCTION/PURPOSE: Fat metabolism and muscle adaptation was investigated in 6 older trained men (age: 61 ± 4 years; VO2max: 48 ± 2 mL kg min) following repeated prolonged exercise).METHODS: 2706 km (1,681 miles) cycling was performed over 14 days and a blood sample and a muscle biopsy were obtained at rest after an overnight fast before and 30 hours after the completion of the cycling. VO2-max and maximal fat oxidation were measured using incremental exercise tests. Heart rate was continuously sampled during cycling to estimate exercise intensity.RESULTS: The daily duration of exercise was 10 hours and 31 ± 37 min and the mean intensity was 53 ± 1 % of VO2max. Body weight remained unchanged. VO2max and maximal fat oxidation rate decreased by 6 ± 2 % (P = 0.04) and 32 ± 8 % (P < 0.01), respectively. The exercise intensity that elicits maximal fat oxidation was not significantly decreased. Plasma free fatty acid (FA) concentration decreased (P < 0.002) from 500 ± 77 to 160 ± 38 μmol L. Plasma glucose concentration as well as muscle glycogen, myoglobin and triacylglycerol content remained unchanged. Muscle citrate synthase (CS)- and ß-hydroxy-Acyl-CoA-dehydrogenase (HAD)- activity were unchanged, but the protein expression of HKII, GLUT4 and ATGL were significantly increased.CONCLUSION: Overall the decreased maximal fat oxidation was probably due to lower exogenous plasma FA availability and the muscle adaptation pattern indicates an increased glucose transport capacity and an increased muscle lipolysis capacity supporting an increased contribution of exogenous glucose and endogenous fat during exercise.
U2 - 10.1249/MSS.0000000000001107
DO - 10.1249/MSS.0000000000001107
M3 - Journal article
C2 - 27685008
VL - 49
SP - 308
EP - 316
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
SN - 0195-9131
IS - 2
ER -