How repeatable are the physiological effects of TENS?
OBJECTIVE
Several studies suggest that transcutaneous electrical stimulation (TENS) can have a variety of effects on the central nervous system (CNS). In this study, we tried to replicate the physiological effects of TENS and to explore its effects on intracortical circuits.


METHODS
We used transcranial magnetic stimulation (TMS) and spinal reflex testing to examine excitability of intracortical and spinal cord circuits before and after a 30-min period of TENS over the flexor carpi radialis (FCR) muscle. We measured the amplitude of TMS-evoked muscle responses (MEP), short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and cortical antagonist inhibition (CAI) in flexor and extensor carpial radialis (FCR, ECR) muscles as well as spinal reciprocal inhibition (RI) and presynaptic inhibition (PI) from ECR to FCR.


RESULTS
TENS had no significant effect on any of these measures apart from a reduction in median nerve induced facilitation of FCR when testing CAI.


CONCLUSIONS
When compared with previous studies, our results suggest that the effects of TENS are highly variable and unreliable, likely by the difficulty in defining precise parameters of stimulation in individual subjects.


CONCLUSIONS
Care should be taken in assuming that effects after TENS observed in small populations of subjects will apply equally to a wider population.
Fernandez-Del-Olmo
Miguel
M
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, London, UK; Facultade de Ciencias do Deporte e a Educación Física, Learning and Motor Control Group, Universidad de A Coruña, Avd. Ernesto Che Guevara 121, Pazos-Liáns, 15179 Oleiros. A Coruña, Spain. Electronic address: mafo@udc.es.
Alvarez-Sauco
Maria
M
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, London, UK; Sección de Neurología, Hospital General Universitario de Elche, Alicante, Spain.
Koch
Giacomo
G
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, London, UK; Laboratorio di Neurologia Clinica e Comportamentale, Fondazione S. Lucia I.R.C.C.S. Rome, Italy.
Franca
Michele
M
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, London, UK; Department of Neurological Sciences, Bellaria Hospital, University of Bologna, Bologna, Italy.
Marquez
Gonzalo
G
Facultade de Ciencias do Deporte e a Educación Física, Learning and Motor Control Group, Universidad de A Coruña, Avd. Ernesto Che Guevara 121, Pazos-Liáns, 15179 Oleiros. A Coruña, Spain.
Sanchez
Jose A
JA
Facultade de Ciencias do Deporte e a Educación Física, Learning and Motor Control Group, Universidad de A Coruña, Avd. Ernesto Che Guevara 121, Pazos-Liáns, 15179 Oleiros. A Coruña, Spain.
Acero
Rafael M
RM
Facultade de Ciencias do Deporte e a Educación Física, Learning and Motor Control Group, Universidad de A Coruña, Avd. Ernesto Che Guevara 121, Pazos-Liáns, 15179 Oleiros. A Coruña, Spain.
Rothwell
John C
JC
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, London, UK.
D000328:Adult; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D018482:Muscle, Skeletal / Q000502:physiology / Q000528:radiation effects; D012018:Reflex; D015203:Reproducibility of Results; D013116:Spinal Cord / Q000502:physiology / Q000528:radiation effects; D004561:Transcutaneous Electric Nerve Stimulation