European Journal of Applied Physiology

, Volume 97, Issue 6, pp 706–715

Strength, size and activation of knee extensors followed during 8 weeks of horizontal bed rest and the influence of a countermeasure

  • E. R. Mulder
  • D. F. Stegeman
  • K. H. L. Gerrits
  • M. I. Paalman
  • J. Rittweger
  • D. Felsenberg
  • A. de Haan
Original Article

DOI: 10.1007/s00421-006-0241-6

Cite this article as:
Mulder, E.R., Stegeman, D.F., Gerrits, K.H.L. et al. Eur J Appl Physiol (2006) 97: 706. doi:10.1007/s00421-006-0241-6

Abstract

Changes in the quadriceps femoris muscle with respect to anatomical cross sectional area (CSA), neural activation level and muscle strength were determined in 18 healthy men subjected to 8 weeks of horizontal bed rest (BR) with (n = 9) and without (n = 9) resistive vibration exercise (RVE). CSA of the knee extensor muscle group was measured with magnetic resonance imaging every 2 weeks during bed rest. In the control subjects (Ctrl), quadriceps femoris CSA decreased linearly over the 8 weeks of bed rest to −14.1 ± 5.2% (P < 0.05). This reduction was significantly (P < 0.001) mitigated by the exercise paradigm (−3.5 ± 4.2%; P < 0.05). Prior to and seven times during bed rest, maximal unilateral voluntary torque (MVT) values of the right leg were measured together with neural activation levels by means of a superimposed stimulation technique. For Ctrl, MVT decreased also linearly over time to −16.8 ± 7.4% after 8 weeks of bed rest (P < 0.01), whereas the exercise paradigm fully maintained MVT during bed rest. In contrast to previous reports, the maximal voluntary activation remained unaltered for both groups throughout the study. For Ctrl, the absence of deterioration of the activation level might have been related to the repeated testing of muscle function during the bed rest. This notion was supported by the observation that for a subset of Ctrl subjects (n = 5) the MVT of the left leg, which was not tested during BR, was reduced by 20.5 ± 10.1%, (P < 0.01) which was for those five subjects significantly (P < 0.05) more than the 11.1 ± 9.2% (P < 0.01) reduction for the right, regularly tested leg.

Keywords

bed restMaximum voluntary torqueVoluntary activationAtrophyCountermeasure

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • E. R. Mulder
    • 1
    • 2
  • D. F. Stegeman
    • 1
    • 2
    • 3
  • K. H. L. Gerrits
    • 1
    • 3
  • M. I. Paalman
    • 3
  • J. Rittweger
    • 4
    • 5
  • D. Felsenberg
    • 4
  • A. de Haan
    • 1
    • 3
    • 5
  1. 1.Institute for Fundamental and Clinical Human Movement SciencesAmsterdamThe Netherlands
  2. 2.918 Department of Clinical Neurophysiology, Institute of NeurologyRadboud University Nijmegen Medical CentreHB, NijmegenThe Netherlands
  3. 3.Faculty of Human Movement SciencesVrije UniversityAmsterdamThe Netherlands
  4. 4.Center for Muscle and Bone researchCharité-Campus Benjamin FranklinBerlinGermany
  5. 5.Institute for Biophysical and Clinical Research into Human MovementManchester Metropolitan UniversityCheshireUK