TY - JOUR
T1 - Repeated Prolonged Exercise Decreases Maximal Fat Oxidation in Older Men
AU - Morville, Thomas
AU - Rosenkilde, Mads
AU - Munch-Andersen, Thor
AU - Andersen, Peter Riis
AU - Kjær Groenbæk, Katja
AU - Helbo, Signe
AU - Kristensen, Marianne
AU - Vigelsø Hansen, Andreas
AU - Mattsson, Nick
AU - Rasmusen, Hanne Kruuse
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 six older trained men (age, 61 ± 4 yr; V-O
2max, 48 ± 2 mL·kg
-1·min
-1) after repeated prolonged exercise). Methods A distance of 2706 km (1681 miles) cycling was performed over 14 d, and a blood sample and a muscle biopsy were obtained at rest after an overnight fast before and 30 h after the completion of the cycling. V-O
2max and maximal fat oxidation were measured using incremental exercise tests. HR was continuously sampled during cycling to estimate exercise intensity. Results The daily duration of exercise was 10 h and 31 ± 37 min, and the mean intensity was 53% ± 1% of V-O
2max. Body weight remained unchanged. V-O
2max 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 μmol·L
-1 to 160 ± 38 μmol·L
-1. Plasma glucose concentration as well as muscle glycogen, myoglobin, and triacylglycerol content remained unchanged. Muscle citrate synthase and ß-hydroxy-acyl-CoA-dehydrogenase activities were unchanged, but the protein expression of HKII, GLUT4, and adipose triacylglycerol lipase were significantly increased. Conclusions Overall, the decreased maximal fat oxidation was probably due to lower exogenous plasma fatty acid 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 six older trained men (age, 61 ± 4 yr; V-O
2max, 48 ± 2 mL·kg
-1·min
-1) after repeated prolonged exercise). Methods A distance of 2706 km (1681 miles) cycling was performed over 14 d, and a blood sample and a muscle biopsy were obtained at rest after an overnight fast before and 30 h after the completion of the cycling. V-O
2max and maximal fat oxidation were measured using incremental exercise tests. HR was continuously sampled during cycling to estimate exercise intensity. Results The daily duration of exercise was 10 h and 31 ± 37 min, and the mean intensity was 53% ± 1% of V-O
2max. Body weight remained unchanged. V-O
2max 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 μmol·L
-1 to 160 ± 38 μmol·L
-1. Plasma glucose concentration as well as muscle glycogen, myoglobin, and triacylglycerol content remained unchanged. Muscle citrate synthase and ß-hydroxy-acyl-CoA-dehydrogenase activities were unchanged, but the protein expression of HKII, GLUT4, and adipose triacylglycerol lipase were significantly increased. Conclusions Overall, the decreased maximal fat oxidation was probably due to lower exogenous plasma fatty acid 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.
KW - Journal Article
UR - http://www.scopus.com/inward/record.url?scp=84989223384&partnerID=8YFLogxK
U2 - 10.1249/MSS.0000000000001107
DO - 10.1249/MSS.0000000000001107
M3 - Journal article
C2 - 27685008
SN - 0195-9131
VL - 49
SP - 308
EP - 316
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
IS - 2
ER -