title: Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply.
abstract: The aim of this study was to compare the training stimuli of eccentric (lengthening) and concentric (shortening) contractions regarding the effect on signaling enzymes involved in protein synthesis. Ten male subjects performed 4 x 6 maximal eccentric contractions on one leg followed by 4 x 6 maximal concentric contractions on the other. Six additional subjects performed the same protocol, but with maximal concentric and submaximal eccentric exercise of equal force to that of the maximal concentric contractions. Muscle biopsy samples were taken from the vastus lateralis before, immediately after, and 1 and 2 h after exercise in both legs. The average peak force produced during the maximal eccentric exercise was 31% higher than during the maximal concentric exercise, 2,490 (+/-100) vs. 1,894 (+/-108) N (P < 0.05). The maximal eccentric contractions led to two- to eightfold increases in the phosphorylation of p70 S6 kinase (p70(S6k)) and the ribosomal protein S6 that persisted for 2 h into recovery but no significant changes in phosphorylation of Akt or mammalian target of rapamycin (mTOR). Maximal concentric and submaximal eccentric contractions did not induce any significant changes in Akt, mTOR, p70(S6k), or S6 phosphorylation up to 2 h after the exercise. The results indicate that one session of maximal eccentric contractions activates p70(S6k) in human muscle via an Akt-independent pathway and suggest that maximal eccentric contractions are more effective than maximal concentric contractions in stimulating protein synthesis in the absence of a nutritional intake, an effect that may be mediated through a combination of greater tension and stretching of the muscle.
authors.affiliation: University College of Physical Education and Sports, Box 5626, Stockholm, S-114 86, Sweden.
authors.forename: Jörgen
authors.initials: J
authors.lastname: Eliasson
authors.forename: Thibault
authors.initials: T
authors.lastname: Elfegoun
authors.forename: Johnny
authors.initials: J
authors.lastname: Nilsson
authors.forename: Rickard
authors.initials: R
authors.lastname: Köhnke
authors.forename: Björn
authors.initials: B
authors.lastname: Ekblom
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology*; D009747:Nutritional Physiological Phenomena; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases
chemical_list: D001786:Blood Glucose; D019344:Lactic Acid; D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases