The present study investigated the relative contribution of the cortical and spinal mechanisms for post-exercise excitability changes in human motoneurons. Seven healthy right-handed adults with no known neuromuscular disabilities performed an isometric voluntary wrist flexion at submaximum continuous exertion. After the subjects continued muscle contraction until volitional fatigue, the H-reflexes induced by an electric stimulation and motor evoked potentials (MEPs) induced by a transcranial magnetic stimulation (TMS) from a flexor carpi radialis (FCR) muscle were recorded 7 times every 20 s. The H-reflex was used to assess excitability changes at the spinal level, and the MEP was used to study excitability changes at the cortical level. H-reflexes showed a depression (30% of control value) soon after the cessation of wrist flexion and recovered with time thereafter. On the other hand, an early (short latency) MEP showed facilitation immediately after the cessation of wrist flexion (50% of control value) and thereafter decreased. A possible mechanism for the contradictory results of the 2 tests, in spite of focusing on the same motoneuron pool, might be the different test potential sizes between them. In addition, a late (long latency) MEP response appeared with increasing exercise. With regard to the occurrence of late MEP response, a central mechanism may be proposed to explain the origin—that is, neural pathways with a high threshold that do not participate under normal circumstances might respond to an emergency level of muscle exercise, probably reflecting central effects of fatigue.
Takashi Kato, Yusaku Takeda, Toshio Tsuji, and Tatsuya Kasai
Sofia I. Lampropoulou and Alexander V. Nowicky
The purported ergogenic actions of transcranial direct current stimulation (tDCS) applied to motor cortex (M1) on force production and perception of effort were investigated using a 10-item numerical rating scale (0–10 NRS) in nonfatiguing bouts of a force-matching task utilizing isometric elbow flexion. Using a crossover design, 12 healthy volunteers received sham, anodal, and cathodal tDCS randomly for 10 min (1.5 mA, 62 μA/cm2) to the left M1 in a double-blind manner. Corticospinal excitability changes were also monitored using transcranial magnetic stimulation (TMS) with surface electromyography (sEMG) to monitor both motor evoked potentials (MEPs) and force-EMG from right m. biceps brachii and m. brachioradialis brachii. No significant differences between the verum and sham stimulation were obtained for elbow flexion maximum voluntary force, perception of effort, or sEMG. There were also no significant differences in MEP changes for the types of tDCS, which is consistent with reports that tDCS excitability effects are diminished during ongoing cognitive and motor activities.
Matthew Harkey, Michelle McLeod, Ashley Van Scoit, Masafumi Terada, Michael Tevald, Phillip Gribble, and Brian Pietrosimone
Altered neuromuscular function and decreased dorsiflexion range of motion (DFROM) have been observed in patients with chronic ankle instability (CAI). Joint mobilizations are indicated for restoring DFROM and dynamic postural control, yet it remains unknown if a mobilization can alter neuromuscular excitability in muscles surrounding the ankle.
To determine the immediate effects of a Maitland grade III anterior-to-posterior joint mobilization on spinal-reflex and corticospinal excitability in the fibularis longus (FL) and soleus (SOL), DFROM, and dynamic postural control.
Single-blinded randomized control trial.
30 patients with CAI randomized into a mobilization (n = 15) or control (n = 15) group.
Maitland grade III anterior-to-posterior joint mobilization.
Main Outcome Measures:
Spinal-reflex excitability was measured with the Hoffmann reflex, while corticospinal excitability was evaluated with transcranial magnetic stimulation. DFROM was measured seated with the knee extended, and dynamic postural control was quantified with the Star Excursion Balance Test. Separate 2 × 2 repeated-measures ANOVAs were performed for each outcome measure. Dependent t tests were used to evaluate individual differences within groups in the presence of significance.
Spinal-reflex and corticospinal excitability of the SOL and FL were not altered in the mobilization or control group (P > .05). DFROM increased immediately after the mobilization (P = .05) but not in the control group, while dynamic postural control was unchanged in both groups (P > .05).
A single joint-mobilization treatment was efficacious at restoring DFROM in participants with CAI; however, excitability of spinal reflex and corticospinal pathways at the ankle and dynamic postural control were unaffected.
Adam S. Lepley, Allison M. Strouse, Hayley M. Ericksen, Kate R. Pfile, Phillip A. Gribble, and Brian G. Pietrosimone
Components of gluteal neuromuscular function, such as strength and corticospinal excitability, could potentially influence alterations in lower extremity biomechanics during jump landing.
To determine the relationship between gluteal muscle strength, gluteal corticospinal excitability, and jump-landing biomechanics in healthy women.
Descriptive laboratory study.
37 healthy women (21.08 ± 2.15 y, 164.8 ± 5.9 cm, 65.4 ± 12.0 kg).
Bilateral gluteal strength was assessed through maximal voluntary isometric contractions (MVIC) using an isokinetic dynamometer. Strength was tested in the open chain in prone and side-lying positions for the gluteus maximus and gluteus medius muscles, respectively. Transcranial magnetic stimulation was used to elicit measures of corticospinal excitability. Participants then performed 3 trials of jump landing from a 30-cm box to a distance of 50% of their height, with an immediate rebound to a maximal vertical jump. Each jump-landing trial was video recorded (2-D) and later scored for errors.
Main Outcome Measures:
MVICs normalized to body mass were used to assess strength in the gluteal muscles of the dominant and nondominant limbs. Corticospinal excitability was assessed by means of active motor threshold (AMT) and motor-evoked potentials (MEP) elicited at 120% of AMT. The Landing Error Scoring System (LESS) was used to evaluate jump-landing biomechanics.
A moderate, positive correlation was found between dominant gluteus maximus MEP and LESS scores (r = .562, P = .029). No other significant correlations were observed for MVIC, AMT, or MEP for the gluteus maximus and gluteus medius, regardless of limb.
The findings suggest a moderate relationship between dominant gluteus maximus corticospinal excitability and a clinical measure of jump-landing biomechanics. Further research is required to substantiate the findings and expand our understanding of the central nervous system’s role in athletic movement.
Sukhvinder S. Obhi, Patrick Haggard, John Taylor, and Alvaro Pascual-Leone
Bimanual coordination tasks form an essential part of our behaviour. One brain region thought to be involved in bimanual coordination is the supplementary motor area (SMA). We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz for 5 min to create a temporary virtual lesion of the rostral portion of the human SMA immediately prior to performance of a goal-directed bimanual coordination task. In two control conditions, participants underwent sham stimulation or stimulation over the primary motor cortex (MI). The experimental task was to open a drawer with the left hand, catch a ball with the right hand, and reinsert the ball into the drawer through an aperture just big enough for the ball to pass through, again with the right hand. Hence, the actions of one hand depend upon the actions of the other. We calculated time intervals between the successive component actions of one hand (unimanual intervals) and actions of both hands (bimanual intervals) and analyzed these intervals separately. Interestingly, none of the unimanual intervals were affected by the rTMS, but the variability of a critical bimanual interval—the time between the left hand opening the drawer and the right hand starting to move to catch the ball—was increased by rTMS over the rostral parts of the SMA. No such effect was seen following rTMS over MI or after sham rTMS. Our results suggest that the rostral parts of the SMA play an important role in aspects of functional bimanual tasks, which involve tight temporal coordination between different motor actions of the two hands.
). BM indicates body mass; EMG, electromyography; RCT, randomized controlled trial; TMS, transcranial magnetic stimulation. Wile E. Coyote image licensed via carlos cardetas/Alamy Stock Photo. In the business, elite-sport, or academic setting, there is never only one way to complete a task, but there is
Julie P. Burland, Adam S. Lepley, Marc Cormier, Lindsay J. DiStefano, and Lindsey K. Lepley
the generation of muscle force. In order to evaluate voluntary motor control, investigators can use measures of corticospinal excitability to quantify descending neural activity and the ability of the motor cortex to activate muscle. To this point, transcranial magnetic stimulation was used to assess
Dustin R. Grooms, Adam W. Kiefer, Michael A. Riley, Jonathan D. Ellis, Staci Thomas, Katie Kitchen, Christopher A. DiCesare, Scott Bonnette, Brooke Gadd, Kim D. Barber Foss, Weihong Yuan, Paula Silva, Ryan Galloway, Jed A. Diekfuss, James Leach, Kate Berz, and Gregory D. Myer
injury prevention program. After a 10-week landing skill training program, participants’ motor cortex (M1) were stimulated using transcranial magnetic stimulation and, relative to strength training, landing training decreased corticomotor excitability in the gluteus maximus (indicating motor learning as
Xiao Bao, Jie-Wen Tan, Ying Long, Howe Liu, and Hui-Yu Liu
repetitive transcranial magnetic stimulation, have few effects for dizziness. 5 It remains a challenge for physicians. Therefore, new approaches in the treatment of dizziness are needed. Intermittent hypoxia training (IHT) is initially recognized by the sports medicine community as a potentially useful
Rafael Gnat, Agata Dziewońska, Maciej Biały, and Martyna Wieczorek
by studying corticospinal projections to the abdominal muscles. They found that transcranial magnetic stimulation of the ipsilateral motor cortex elicited responses from both ipsi- and contralateral transversus abdominis muscles, suggesting simultaneous engagement of the crossed and uncrossed