Submitted on December 18, 2008
Revised on February 17, 2009
Accepted on February 18, 2009
EFFECT OF FUNCTIONAL ELECTROSTIMULATION ON IMPAIRED SKIN VASODILATOR RESPONSES TO LOCAL HEATING IN SPINAL CORD INJURY
Noortje T.L. van Duijnhoven1, Thomas W.J. Janssen2, Daniel J. Green3, Christopher Todd Minson4, Maria T.E. Hopman5, and Dick H.J. Thijssen6*
1 Radboud University Nijmegen
2 Human Movement Sciences, Free University, Amsterdam, the Netherlands
3 Liverpool John Moores University
4 University of Oregon
5 Radboud University Nijmegen Medical Centre
6 University Medical Centre Nijmegen
* To whom correspondence should be addressed. E-mail: d.thijssen{at}fysiol.umcn.nl.
Spinal cord injury (SCI) induces vascular adaptations below the level of the lesion, such as impaired cutaneous vasodilation. However, the mechanisms underlying these differences are unclear. The aim of this study is to examine arm and leg cutaneous vascular conductance (CVC)-responses to local heating in 17 able-bodied controls (39±13 years) and 18 SCI subjects (42±8 years). SCI subjects were counterbalanced for functional electro-stimulation(FES)-cycling exercise (SCI-EX, n=9) or control (SCI-C, n=9) and re-analyzed after 8 weeks. Arm and leg SkBF was measured by laser-Doppler flowmetry during local heating (42°C), resulting in an axon-reflex mediated first peak, nadir and a primarily NO-dependent plateau-phase. Data were expressed as a percentage of maximal CVC (%CVCmax; 44°C). CVC-responses to local heating in the paralyzed leg, but also in the forearm of SCI subjects, were lower than in able-bodied controls (P<0.05 and 0.01, respectively). The 8-week intervention did not change forearm and leg CVC-responses to local heating in SCI-C and SCI-EX, but increased femoral artery diameter in SCI-EX (P<0.05). Interestingly, findings in skin microvessels contrast with conduit arteries, where physical (in)activity contributes to adaptations in SCI. The lower CVC-responses in the paralyzed legs might suggest a role for inactivity in SCI, but the presence of impaired CVC-responses in the normally active forearm suggests other mechanisms. This is supported by a lack of adaptation in skin microcirculation after FES-cycle training. This might relate to the less frequent and smaller magnitude of skin blood flow responses to heat stimuli compared with controls, than physical inactivity per se.
