title: Motor cortex fatigue in sports measured by transcranial magnetic double stimulation.
abstract: OBJECTIVE
  Besides peripheral mechanisms, central fatigue is an important factor limiting the performance of exhausting exercise in sport. The mechanisms responsible are still in discussion. Using noninvasive transcranial magnetic stimulation (TMS) in a double-pulse technique, we sought to assess fatigue of the motor cortex after exhaustive anaerobic strain.
  
  
  METHODS
  23 male subjects (22-52 yr) taking part in the study were requested to accomplish as many pull-ups as possible until exhaustion. The amount of physical lifting work was recorded. Before and immediately after the task, intracortical inhibition (ICI) and facilitation (ICF) were measured by a conditioned-test double-pulse TMS method for the right brachioradialis (BR) and abductor pollicis brevis muscle (APB).
  
  
  RESULTS
  After exercise, ICF was significantly reduced in the BR but not in the APB. ICI was not altered. Changes tended to normalize within 8 min after the task. The amount of lifting work accomplished showed significant correlation to the values of ICF reduction (r = 0.73). Moreover, the baseline values of ICF before exercise were also significantly correlated to the lifting work (r = 0.63).
  
  
  CONCLUSIONS
  Because double-pulse TMS gives access to the motor cortex independently of spinal or peripheral mechanisms, reduced ICF reflects decreased excitability of interneuronal circuits within the motor cortex. We suggest that ICF measures motor cortex fatigue after exhausting strain specifically for the muscles performing the task. Gamma-aminobutyric acid (GABA)-ergic neurotransmission is possibly involved in the mechanisms mediating central fatigue. Double-pulse TMS may be a useful tool in the control of training in sports as well as in the detection of pathological central fatigue in overreaching and in the prevention of overtraining.
authors.affiliation: Department of Clinical Neurophysiology, University of Göttingen, Germany. f.tergau@med.uni-goettingen.de
authors.forename: F
authors.initials: F
authors.lastname: Tergau
authors.forename: R
authors.initials: R
authors.lastname: Geese
authors.forename: A
authors.initials: A
authors.lastname: Bauer
authors.forename: S
authors.initials: S
authors.lastname: Baur
authors.forename: W
authors.initials: W
authors.lastname: Paulus
authors.forename: C D
authors.initials: CD
authors.lastname: Reimers
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold; D006801:Humans; D017770:Lifting; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D005680:gamma-Aminobutyric Acid