title: Collagen content in the vastus lateralis and the soleus muscle following a 90-day bed rest period with or without resistance exercises.
abstract: BACKGROUND
  spaceflight seems associated with deterioration of the function of the skeletal muscles. Since muscle collagen is critical for muscle function, an improved understanding of the content of the muscle collagen during long-term inactivity seems important. Bed-rest with in-bed resistance training serves as a proxy for the conditions in space. Therefore, ground-based studies may improve the understanding of the consequences of long-term inactivity.
  
  
  OBJECTIVE
  the purpose is to compare the change in collagen protein in the vastus lateralis (VL) and the soleus (SOL) muscle amongst persons exposed to a 90-day bed rest with or without resistance exercise.
  
  
  METHODS
  an explorative analysis was completed based on data from a randomized, controlled trial. The intervention group (BRE, SOL n=4, VL n=8) performed supine-based squat exercises, whereas the controls (BE, SOL n=6, VL n=12) remained inactive during follow-up. Muscle biopsies from vastus lateralis and soleus were taken at baseline (pre) and after 90-days' follow-up (post). Muscle collagen (μg collagen/mg protein) was quantified. Two-way repeated measurements ANOVA was used to compare the interaction between the intervention (BRE/BR) and time (pre/post) for each muscle.
  
  
  RESULTS
  the collagen content of VL was similar between pre and post in the BRE group (-3.8 μg collagen/mg protein [95% CI: -22.0; 14.4], p=0.68) while it rose amongst individuals in the BR group (14.9 μg collagen/mg protein [95% CI: -0.01; 29.7], p=0.05). The difference of 18.66 [95% CI: -6.5; 43.9] between BRE and BR across time was, however, not significant (p=0.14). No significant reduction in SOL muscle collagen content was observed from pre to post in the BR group (-9.3 μg collagen/mg protein [95% CI: -24.9; 6.4], p=0.25) or in the BRE group (-6.5 μg collagen/mg protein [95% CI: -25.6; 12.6], p=0.50). There was no difference in the effect of BR versus BRE over time (mean difference -2.78 μg collagen/mg protein [95% CI: -29.7; 24.1], p=0.82).
  
  
  CONCLUSIONS
  muscle collagen content in the VL or SOL muscle does not seem to differ after a 90-day bed rest period with or without squat exercises.
authors.affiliation: Department of Public Health, Section of Sport Science, Aarhus University, Denmark; Copen Rehab, Section for Social Medicine, Department of Public Health, University of Copenhagen, Denmark.
authors.forename: Rasmus Oestergaard
authors.initials: RO
authors.lastname: Nielsen
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Tesch
authors.affiliation: Department of Integrative Medical Biology, laboratory of Muscle Biology, Umeå University, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Stål
authors.affiliation: Copen Rehab, Section for Social Medicine, Department of Public Health, University of Copenhagen, Denmark.
authors.forename: Henning
authors.initials: H
authors.lastname: Langberg
keywords: bed rest; collagen; exercise; muscle; spaceflight