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Tuesday, June 6, 2023

Gluteus Maximus Activation (More Glute & Less Hamstring)

Brent Brookbush

Brent Brookbush


Research Review: Optimal Positioning for Gluteus Maximus Activation

By Dr. Stefanie DiCarrado DPT, PT, NASM CPT & CES

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

Original Citation: Kan, S., Jeon, H., Kwon, O., Cynn, H., Choi, B. (2013). Activation of the gluteus maximus and hamstring muscles during prone hip extension with knee flexion in three hip abduction positions. Manual Therapy 18, 303-307 - ABSTRACT

Prone hip extension with knee bent

Why is this relevant?: The gluteus maximus  is a commonly under-active muscle within the predictive models of Lumbo Pelvic Hip Complex Dysfunction (LPHCD) and Sacroiliac Joint Dysfunction (SIJD) . This particular article focuses on the gluteus maximus  as the prime mover of hip extension. The hamstrings (biceps femoris semimembranosus and semitendinosus ) and adductor magnus  are synergistic muscles contributing to hip extension, with the biceps femoris likely contributing most to hip extension force production after the gluteus maximus. Synergists tend to become overactive to compensate for a weak or inhibited prime mover. Therefore, an exercise that allows for optimal alignment of the gluteus maximus  while limiting over activity in the hamstrings provides a highly specific, and therefore highly effective, means of improving gluteus maximus  strength, efficiency, and function.

Note the difference in fiber alignment of the gluteus maximus and collective hamstring musculature.

Study Summary

Study DesignExperimental
Level of EvidenceIIA - Evidence from at least one controlled study without randomization
Subject Demographics
  • Mean Age: 22.8 + 2.9 yr
  • Gender: 18 men, 12 women
  • Characteristics: healthy subjects without history of lumbar, sacroiliac, or leg pain within the previous year; without impairments/diseases of the neuromuscular or cardiovascular systems; without shortening of the iliacus, psoas, TFL, or adductors as determined via Thomas Test, Ober's Test, Adduction Contracture Test respectively; without hip/lumbar pain during prone hip extension, active/passive straight leg raise, or hip flexion, adduction, and internal rotation.
    • Mean Body Mass: 66.9 + 10.8 kg
    • Mean Height: 170.3 + 4.1 cm

Outcome Measures
  • For both gluteus maximus and hamstrings:
    • EMG amplitude: the intensity of the electrical activity within the muscle
    • Relative EMG onset difference: which muscle turned on first during the movement.

  • Results
  • Hamstring EMG (HS)
    • Statistically significant: Highest EMG amplitude at 0 degrees abduction; no significant difference between 15 degrees and 30 degrees abduction (however the mean amplitude was higher at 15 degrees than 30 degrees abduction)

  • Gluteus Maximus EMG (GM)
    • Statistically significant: Highest EMG amplitude at 30 degrees abduction; lowest EMG amplitude at 0 degrees abduction.

  • Relative Onset of Muscle Activity
    • Statistically significant: Earlier onset of HS activity vs GM activity with 0 degrees hip abduction; earlier onset of GM activity vs HS activity with 15 degrees and 30 degrees abduction.
    • The greatest difference of relative onset of muscle activity occurred at 0 degrees hip abduction, then at 15 degrees. The smallest difference occurred at 30 degrees abduction

  • Gluteus Maximus had a higher EMG amplitude than the hamstrings in all hip abduction positions.
ConclusionsWhen looking to activate the gluteus maximus while limiting recruitment of hamstring musculature in prone hip extension with a bent knee, the best hip position is 15-30 degrees of abduction.
Conclusions of the ResearchersMotor unit recruitment activity within the gluteus maximus muscle increased the greatest amount with 30 degrees of abduction during prone hip extension with knee flexion.  In contrast, the hamstrings exhibited the greatest activity with 0 degrees of hip abduction during the same movement pattern. Further, the gluteus maximus motor units fired earlier than those of the hamstrings with 15-30 degrees of abduction and fired later at 0 degrees.  Therefore it can be proposed that the gluteus maximus is most efficient as a prime mover of hip extension at 30 degrees of hip abduction.

Note the oblique fiber alignment and attachment sites of the gluteus maximus. Hip abduction during extension provides a direct line of pull which increases gluteus maximus activation.

Review & Commentary:

The overall methodology for this study was strong despite the small sample size. Subject selection protected against potential errors by removing those with altered length tension relationships of hip musculature. The sample represented a young healthy population without injury or major muscle imbalance of the iliacus , psoas , TFL , or adductors  . The EMG data gathered is therefore assumed to represent "normal" muscle activation patterns. Researchers implemented clear processes and procedures to improve the validity of the data obtained. Hip extension was performed with a bent knee to place the hamstrings into a position of active insufficiency therefore limiting excessive synergistic assistance. Further, researchers standardized the assessment by creating a structure of wooden boards that guided the appropriate amount of hip abduction required and prevented excessive knee flexion or hip rotation during hip extension. Deviations relative to the wooden structure were visually noted by the examiners. If deviations were observed, data for those repetitions was discarded. Subjects practiced the task for 5 minutes to eliminate errors of unfamiliarity. To ensure the validity and integrity of surface EMG data, researchers placed the gluteal EMG electrode at an oblique angle to match the muscle fiber orientation.

Measurements were determined by averaging three trials in each plane of hip abduction with 30 seconds rest in between each trial. Subjects rested two minutes between each testing position. The degree of abduction used in a particular trial was determined randomly via a computer program and was referenced using a line drawn from the subject's ASIS through the center of the subject's patella.

Researchers adequately described the equipment used and the experimental process so that one could replicate the study with a different population or larger sample size. However, this study is not without limitations. Researchers were careful to minimize compensatory knee and hip movement patterns but did not consider lumbar extension during hip extension. Lumbar extension due to the erector spinae  acting as an over-active synergist is a common compensatory movement pattern for weak or inhibited gluteal musculature noted in the predictive model of LPHCD . In the context of this study, it is unclear if any subject achieved the desired end position (holding the patella 5cm above the table) using pure hip extension or if any used compensatory lumbar extension. Additionally, researchers evaluated shortened muscles and the presence of pain but did not assess other movement impairments that could indicate poor hip biomechanics. Such as, improper anterior and/or superior glide of the femoral head (as noted by movement of the greater trochanter), limited or excessive sacral nutation or counternutation, and/or pelvic torsion may result in altered recruitment patterns and firing rates and therefore, relative latent firing the prime mover. This scenario is unlikely given the similarity of the data points collected, but is worth noting.

The employment of surface electrodes over needle electrodes introduces the risk of interference from other muscles. The placement of the EMG electrode between the greater trochanter and the S2 vertebra may allow for potential interference from the piriformis  and deep rotators of the hip . These muscles are commonly overactive; however, such interference may be unlikely given their depth and the placement of the electrode on the center of the gluteus maximus  muscle belly. The authors chose to use only one electrode for gluteus maximus  and one electrode for the hamstring muscles which is potentially a standard set up, but since these are muscles that cover a large area, perhaps the study would have benefited from the use of two separate EMG machines with two electrodes per muscle.

Future studies should observe if one of the hamstring muscles over fires when compared to the others. For example, was it the biceps femoris that became synergistically dominant, the semi's, or both muscles sets of muscles. Further, a potential oversight in this study was the exclusion of the posterior fibers of adductor magnus, a muscle that has the potential to become synergistically dominant for the gluteus maximus and may have been inhibited by the abduction used in the study. Last, it would be interesting to evaluate gluteus maximus  and hamstring EMG activity with hip extension with the knee extended (attempting to reciprocally inhibition the hamstrings with quadriceps activation) and compare those findings with those found in this study.

Why is this study important?

This research is important because it clarified the relationship between a prime mover and its synergist during a particular movement pattern. Specifically, it documented gluteus maximus  and hamstring (biceps femoris , semimembranosus, and semitendinosus ) activity during prone hip extension with a bent knee at different degrees of hip abduction (0 degrees, 15 degrees, 30 degrees).

The authors discussed possible explanations for their findings including the alignment of gluteus maximus  muscle fibers during hip abduction and the fact that it is a fusiform muscle, along with the balanced neuromuscular interactions between a prime mover and synergists. Fusiform muscle fibers run parallel to the long axis of the muscle and generate direct tension as the muscle contracts. This allows for greater overall tension in the muscle, but will diminish force production if the line of pull is angled. The gluteus maximus  fibers run obliquely as they course from the pelvic girdle to the attachment sites on the femur and iliotibial band, and therefore hip abduction may improve muscle recruitment through better fiber alignment. The interaction between the neurological and musculoskeletal system is something that requires more attention. When the efficiency of a prime mover can be enhanced, such as what may occur in the gluteus maximus  with 15 degrees (or more) of hip abduction, synergistic muscles will likely be less capable of dominating activity; however, the role of reciprocal inhibition, relative length and activation threshold, and tone also need further consideration. This is demonstrated by the relative EMG onset difference outcome measure. In 0 degrees of hip abduction, the hamstrings fired first with greater intensity because the gluteus maximus  fibers did not have optimal alignment for motor unit recruitment. However, in 15 and 30 degrees of abduction, the gluteus maximus  fired sooner than the hamstrings and with greater intensity.

Human movement professionals require anatomical and biomechanical knowledge to implement appropriate exercise programs when addressing movement impairment. Understanding the optimal position for muscle activation is essential to successful exercise selection and program design. This study provides to the professional, evidence of an optimal line of pull to better activate an inhibited and/or weak gluteus maximus  while limiting compensatory synergistic actions of the hamstrings.

How does this affect practice?

Prone hip extension with a bent knee is a commonly used gluteus maximus  manual muscle test and strengthening position. Performing hip abduction while extending the hip with a bent knee offers better recruitment of the gluteus maximus  and limits synergistic assistance of the hamstrings. As mentioned above, the specificity of this exercise execution plays upon the alignment of the gluteus maximus  muscle (traveling in an inferolateral direction) and the innate structure of the muscle itself. Additionally, once the gluteus maximus  is activated, the nervous system will minimize output to its synergists to create pure hip extension without compensation.

In addition to increasing gluteus maximus  activation for rehabilitation or strengthening purposes, the addition of hip abduction greater than 15 degrees may also provide a more optimal manual muscle test position when looking to isolate the gluteus maximus . One must remember if employing this method to document the degree of abduction used for consistency between assessments.

How does it relate to Brookbush Institute Content?

The Brookbush Institute has always promoted slight hip abduction when performing gluteus maximus  activation exercises. As this article demonstrates, hip extension performed with hip abduction properly align the muscle fibers of the gluteus maximus  for optimal force production. Additionally, adding hip abduction reduces synergistic involvement of the adductor magnus , another muscle that assists with hip extension. It is the vision of the Brookbush Institute to provide evidence-based practical education. This article is another piece in the search for congruence when addressing movement impairment within the context of LPHCD  adding supportive research to a cue used in all gluteus maximus activation exercise.

Glutues Maximus Isolated Activation

TVA and Gluteus Maximus Activation and Progressions

Quick Glute Activation Circuit:

© 2014 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged -