Four weeks of speed endurance training reduces energy expenditure during exercise and maintains muscle oxidative capacity despite a reduction in training volume

• Published in: Journal of applied physiology (1985) Vol. 106; no. 1; pp. 73 - 80
• Main Authors: Iaia, F. Marcello, Hellsten, Ylva, Nielsen, Jens Jung, Fernstrom, Maria, Sahlin, Kent, Bangsbo, Jens
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.01.2009; American Physiological Society
• Subjects: Adaptation, Physiological; Adult; Biological and medical sciences; Body Weight; Capillaries - pathology; Energy Metabolism; Exercise; Fundamental and applied biological sciences. Psychology; Gene expression; Heart Rate; Human subjects; Humans; Ion Channels - metabolism; Lactic Acid - blood; Longitudinal Studies; Male; Medicin och hälsovetenskap; Mitochondria, Muscle - enzymology; Mitochondria, Muscle - metabolism; Mitochondrial Proteins - metabolism; Muscle Fibers, Skeletal - metabolism; Muscle, Skeletal - blood supply; Muscle, Skeletal - metabolism; Muscle, Skeletal - pathology; Musculoskeletal system; Oxidative Phosphorylation; Oxygen Consumption; Physical Endurance; Pulmonary Ventilation; Respiratory Mechanics; Running; Studies; Time Factors; Uncoupling Protein 3; Physical exercise; 3-Hydroxyacyl-CoA dehydrogenase; Physical training; Uncoupling protein; fiber type distribution; Enzyme; oxygen uptake; Oxygen consumption; Striated muscle; citrate synthase; Vertebrata; Mammalia; Energetic cost; uncoupling protein 3; Distribution; Endurance; Oxidoreductases
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.90676.2008

1 Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark; 2 Faculty of Exercise Sciences, State University of Milan, Milan, Italy; 3 Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and 4 Department of Sports and Health Science, Stockholm University College of Physical Education and Sports, Stockholm, Sweden Submitted 21 May 2008 ; accepted in final form 1 October 2008 We studied the effect of an alteration from regular endurance to speed endurance training on muscle oxidative capacity, capillarization, as well as energy expenditure during submaximal exercise and its relationship to mitochondrial uncoupling protein 3 (UCP3) in humans. Seventeen endurance-trained runners were assigned to either a speed endurance training (SET; n = 9) or a control (Con; n = 8) group. For a 4-wk intervention (IT) period, SET replaced the ordinary training ( 45 km/wk) with frequent high-intensity sessions each consisting of 8–12 30-s sprint runs separated by 3 min of rest (5.7 ± 0.1 km/wk) with additional 9.9 ± 0.3 km/wk at low running speed, whereas Con continued the endurance training. After the IT period, oxygen uptake was 6.6, 7.6, 5.7, and 6.4% lower ( P < 0.05) at running speeds of 11, 13, 14.5, and 16 km/h, respectively, in SET, whereas remained the same in Con. No changes in blood lactate during submaximal running were observed. After the IT period, the protein expression of skeletal muscle UCP3 tended to be higher in SET (34 ± 6 vs. 47 ± 7 arbitrary units; P = 0.06). Activity of muscle citrate synthase and 3-hydroxyacyl-CoA dehydrogenase, as well as maximal oxygen uptake and 10-km performance time, remained unaltered in both groups. In SET, the capillary-to-fiber ratio was the same before and after the IT period. The present study showed that speed endurance training reduces energy expenditure during submaximal exercise, which is not mediated by lowered mitochondrial UCP3 expression. Furthermore, speed endurance training can maintain muscle oxidative capacity, capillarization, and endurance performance in already trained individuals despite significant reduction in the amount of training. uncoupling protein 3; citrate synthase; 3-hydroxyacyl-CoA dehydrogenase; oxygen uptake; fiber type distribution Address for reprint requests and other correspondence: J. Bangsbo, Dept. of Exercise and Sport Sciences, August Krogh Bldg., Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark (e-mail: jbangsbo{at}aki.ku.dk )