Anabolic signaling and protein synthesis in human skeletal muscle after dynamic shortening or lengthening exercise

Am J Physiol Endocrinol Metab. 2006 Apr;290(4):E731-8. doi: 10.1152/ajpendo.00415.2005. Epub 2005 Nov 1.


We hypothesized a differential activation of the anabolic signaling proteins protein kinase B (PKB) and p70 S6 kinase (p70(S6K)) and subsequent differential stimulation of human muscle protein synthesis (MPS) after dynamic shortening or lengthening exercise. Eight healthy men [25 +/- 5 yr, BMI 26 +/- 3 kg/m(-2) (means +/- SD)] were studied before and after 12 min of repeated stepping up to knee height, and down again, while carrying 25% of their body weight, i.e., shortening exercise with the "up" leg and lengthening exercise with contralateral "down" leg. Quadriceps biopsies were taken before and 3, 6, and 24 h after exercise. After exercise, over 2 h before the biopsies, the subjects ingested 500 ml of water containing 45 g of essential amino acids and 135 g of sucrose. Rates of muscle protein synthesis were determined via incorporation over time of [1-(13)C]leucine (<or=6 h after exercise) or [1-(13)C]valine (21-24 h after exercise) and phosphorylation of signaling proteins by Western analysis. PKB and p70(S6K) phosphorylation increased approximately 3-fold after 3 h and remained elevated at 6 and 24 h. After exercise, rates of myofibrillar and sarcoplasmic protein synthesis were unchanged over the period including exercise and 3 h of recovery but had increased significantly at 6 (approximately 3.0- and 2.4-fold, respectively) and 24 h (approximately 3.2- and 2.0-fold, respectively), independently of the mode of exercise. Short-term dynamic exercise in either shortening or lengthening mode increases MPS at least as much as resistance exercise and is associated with long-term activation of PKB and p70(S6K).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Biopsy
  • Blotting, Western
  • Collagen / biosynthesis
  • Exercise / physiology*
  • Humans
  • Leucine / blood
  • Leucine / metabolism
  • Male
  • Muscle Proteins / biosynthesis*
  • Myofibrils / metabolism
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quadriceps Muscle / enzymology
  • Quadriceps Muscle / metabolism*
  • Random Allocation
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Sarcoplasmic Reticulum / metabolism
  • Signal Transduction / physiology
  • Valine / blood
  • Valine / metabolism


  • Muscle Proteins
  • Collagen
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Leucine
  • Valine