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June 6, 2023

Evidence of Altered Corticomotor Excitability Following Targeted Activation of Gluteus Maximus Training in Healthy Individuals

Discover how targeted gluteus maximus training can alter corticomotor excitability in healthy individuals with our evidence-based article. Learn more now!

Brent Brookbush

Brent Brookbush

DPT, PT, MS, CPT, HMS, IMT

Research Review: Evidence of Altered Corticomotor Excitability Following Targeted Activation of Gluteus Maximus Training in Healthy Individuals

By Jacky Au PhD, CPT

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation:

Fisher, B. E., Southam, A. C., Kuo, Y. L., Lee, Y. Y., & Powers, C. M. (2016). Evidence of altered corticomotor excitability following targeted activation of gluteus maximus training in healthy individuals. Neuroreport, 27(6), 415-421. ABSTRACT

Introduction:

The gluteal complex (gluteus maximus , medius , and minimus ) is often targeted during lower-extremity rehabilitation and strengthening programs. Specifically, activation exercises are recommended for the gluteus maximus (GM ) to preferentially recruit the muscle, increase neuromuscular drive and enhance recruitment (1). The goal of this 2016 study from the University of Southern California was to study the neural changes associated with GM activation exercise. Using combined neurostimulation and electromyography (EMG) methods, researchers found increased excitatory and inhibitory inputs to the GM after intervention. This may imply that GM activation  is effective in part due to enhanced corticomotor adaptations.

Image of Transcranial Magnetic Stimulator (TMS)
Caption: Image of Transcranial Magnetic Stimulator (TMS)

Transcranial Magnetic Stimulator (TMS) By Baburov - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=39754391

Study Summary

Study DesignCase Series
Level of EvidenceIII Observational Study
Participant Characteristics

Sample:

Demographics

  • Age: 23-40 years (mean: 27.7)
  • Number of participants: 12 (7 men, 5 women)

Inclusion Criteria:

  • Physically active
  • No current lower-extremity injury or pain

Exclusion Criteria:

  • History of neurological or psychiatric disorders, including:
    • Seizures
    • Epilepsy
    • Migraine

  • Electrical, magnetic, or metal devices implanted in body
  • History of unexplained loss of consciousness
  • Medication or alcohol use within the previous 12 hours
  • Possible pregnancy
MethodologyNeuromuscular Measurements (pre- and post-intervention)
  • Neuromuscular efficiency between the motor cortex and the gluteus maximus (GM) were measured through the combined use of Transcranial magnetic stimulation (TMS) and electromyography (EMG)
  • TMS was used to stimulate the motor cortex through electromagnetic induction and electromyography (EMG) was used to measure the subsequent amount of muscle activity in the GM (see reference 5 for a review of this technique).

At-Home Exercise Intervention

  • 60-minutes of daily training, broken down into three 20-minute segments for 6 days.
  • Each 20-minute segment involved static holds with a resistance band for up to 1-minute at a time.
    • If 1-minute could not be accomplished by participants, then they were instructed to hold the position until fatigue.

  • Exercise involved extension (45 degrees), abduction (45 degrees), and external rotation (30 degrees) of the right hip, starting in the quadruped position (see Figure 2).
  • Compliance was measured through self-report.
Data Collection and AnalysisData Collection
  • TMS coil placement was determined by finding the area over the motor cortex that elicited the strongest GM contraction.
  • TMS pulses were delivered at stimulation intensities of 25%, 35%, 45%, 55%, and 65% of the maximum stimulator output.
  • EMG electrodes were placed on the right GM midway between the greater trochanter and second sacral vertebra to measure strength of TMS-driven muscle contractions.

Data Analysis

  • Neural changes were assessed using paired t-tests to compare the slopes of input-output curves before and after intervention.
  • Input-output curves plotted EMG strength against TMS intensity, such that steeper curves represented stronger muscle output for a given level of neural input.
  • An additional paired t-test was run to compare EMG strength only at the highest stimulation intensity of 65%. 
Outcome Measures
  • Motor-evoked potentials to measure neural excitability
  • Cortical silent periods to measure neural inhibition
Results
  • Input-output curve slopes were significantly greater at post-test for both MEPs (indicating stronger neural excitability, p<.01) and CSPs (indicating stronger neural inhibition p=.04).
  • Looking only at the maximum stimulation intensity of 65%, larger MEP amplitudes (p=.04) and longer CSP durations (p=.01) were also detected after intervention.
Researchers' Conclusions

Excitatory and inhibitory neural inputs to the GM can be increased with GM activation training, which may facilitate targeted use of the GM during rehabilitation or strength programs.

How this study contributes to the body of research:

A one-week home training program of gluteus maximus (GM ) activation resulted in a significant increase in corticomotor excitability as well as changes in inhibitory processes of the GM . Prior research has demonstrated adaptations of the motor cortex following exercise; however, the exercises were complex movements and adaptation was attributed to skill acquisition (3-8). Unique to this study is the demonstration that motor cortex adaptations occur and may contribute to the benefits achieved by GM activation; a movement pattern requiring minimal skill.

How the Findings Apply to Practice:

This study not only demonstrated that motor cortex adaptations occur and may contribute to the benefits achieved by GM activation , but that these adaptations were achieved using an exercise that was recommended for home use. Assessment of GM strength should be included for individuals exhibiting signs of Lumbopelvic Hip Complex Dysfunction , Sacroiliac Dysfunction , and/or Lower-Extremity Dysfunction . The inclusion of GM activation techniques can be confidently recommended for supervised and in-home programs.

Strengths

  1. The use of transcranial magnetic stimulation and motor evoked potentials was a novel way to investigate the neuromuscular adaptations to corrective/therapeutic exercise.
  2. This study filled a gap in the research by demonstrating that simple exercise techniques resulted in corticomotor adaptation, as opposed to previous studies that demonstrated adaptation to more complex tasks.
  3. Neuro-navigation increased intra-subject reliability of TMS coil placement.
  4. Minimal equipment was required for this exercise, making it easily applicable to practice.

Weaknesses and Limitations

  1. The cohort consisted of injury/pain-free participants; therefore, generalizability to those with lumbar spine, hip or lower-extremity injuries is limited.
  2. The study did not mention if the participants had exercise experience, which may influence additional motor learning or corticomotor adaptations.
  3. It is unfortunate that GM  strength was not assessed to determine if adaptation was dependent on level of inhibition/strength.

How the study relates to Brookbush Institute Content?

The Brookbush Institute (BI) continues to develop and refine predictive models of dysfunction, such as Lumbo-Pelvic-Hip Complex Dysfunction (LPHCD) , to aid in education and practical application of human movement science research. This study demonstrates that corticomotor adaptations may contribute to the effectiveness of activation techniques, and that one-week of GM activation  was sufficient to result in corticomotor adaptations. The BI will continue to integrate studies like this to enhance understanding of corrective interventions, refine recommendations, and pursue an evidence-based, systematic approach for attaining optimal outcomes.

The following videos illustrate common interventions used for gluteus maximus activation :

Gluteus Maximus Isolated Activation

http://player.vimeo.com/video/82855853

Transverse Abdominis and Gluteus Maximus Activation and Progressions

http://player.vimeo.com/video/82877282

Gluteus Maximus Reactive Activation

http://player.vimeo.com/video/76690982

Gluteus Maximus Reactive Activation Progressions

http://player.vimeo.com/video/76690880

Bibliography:

  1. Reiman MP, Bolgla LA, Loudon JK. A literature review of studies evaluating gluteus maximus and gluteus medius activation during rehabilitation exercises. Physiotherapy Theory and Practice. 2012 May 1;28(4):257–68.
  2. Fitzgerald PB, Fountain S, Daskalakis ZJ. A comprehensive review of the effects of rTMS on motor cortical excitability and inhibition. Clinical Neurophysiology. 2006 Dec 1;117(12):2584–96.
  3. Gallasch E, Christova M, Krenn M, Kossev A, Rafolt D. Changes in motor cortex excitability following training of a novel goal-directed motor task. Eur J Appl Physiol. 2009 Jan;105(1):47–54.
  4. Hirano M, Kubota S, Koizume Y, Funase K. Acquisition of motor memory determines the interindividual variability of learning-induced plasticity in the primary motor cortex. Journal of Applied Physiology. 2018 Jul 5;125(4):990–8.
  5. Cirillo J, Todd G, Semmler JG. Corticomotor excitability and plasticity following complex visuomotor training in young and old adults. Eur J Neurosci. 2011 Dec;34(11):1847–56.
  6. Tennant KA, Adkins DL, Scalco MD, Donlan NA, Asay AL, Thomas N, et al. Skill learning induced plasticity of motor cortical representations is time and age-dependent. Neurobiol Learn Mem. 2012 Oct;98(3):291–302.
  7. Dayan E, Cohen LG. Neuroplasticity Subserving Motor Skill Learning. Neuron. 2011 Nov 3;72(3):443–54.
  8. Kawai R, Markman T, Poddar R, Ko R, Fantana AL, Dhawale AK, et al. Motor Cortex Is Required for Learning but Not for Executing a Motor Skill. Neuron. 2015 May 6;86(3):800–12.
  9. Wilson J, BPhty EF, BPhty AH, Maitland L, BPhty CT. A structured review of the role of gluteus maximus in rehabilitation. New Zealand Journal of Physiotherapy. 2005 Nov;33(3) 95-100.
  10. Jonkers I, Stewart C, Spaepen A. The complementary role of the plantarflexors, hamstrings and gluteus maximus in the control of stance limb stability during gait. Gait & Posture. 2003 Jun 1;17(3):264–72.

© 2019 Brent Brookbush

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