The gluteal muscles in general are responsible for hip extension and rotary movements of the hip (Macadam et al., 2015). The gluteus maximus muscle has been coined as the biggest muscle group in the body, “accounting for about 16% of the total cross-sectional area” (Buckthorpe et al., 2019). One of the major problems with weakness in the gluteal muscle is the compensation patterns that develop thereafter. Since the gluteus maximus is the primary hip extensor (Neto et al., 2020), any functional activities such as walking, jogging, going up and down the stairs, let alone athletic activities such as jumping and change of directions will be affected. The superior portion of the gluteus maximus has shown to have major responsibilities in abduction and external rotation torque, which prevents the hip from entering a gravity facilitated collapse, which has shown to have implications on knee and ankle injuries (although still debatable; Buckthorpe et al., 2019); the same study stated that the inferior gluteus maximus facilitates adduction torque of the hip. The gluteus medius spans a good portion of the pelvis from anterior to posterior in relation to the greater trochanter, hence, it has responsibilities for both internal and external rotation of the hip joint depending on the positioning of the hip. One of the main responsibilities other than hip extension and rotary stability of the glut muscles is providing lumbo-pelvic stability during weight bearing tasks via its connection to the thoracolumbar fascia and the SI joint.
In practice, it is very often that I find clinical relevance between the contralateral QL/oblique/latissimus dorsi tension/strength (tested by manual muscle tests) and ipsilateral gluteus maximus/medius weakness, demonstrating a possible presence of posterior oblique/functional back line dysfunction. These compensation pattern allows clients to be able to perform functional activities such as a bilateral squat or unilateral squat, albeit presenting biomechanics deviations downstream or upstream along the kinetic chain, such as in the lower back, knee, and ankles (Buckthorpe et al., 2019). Another possible compensation strategy with weakness of the gluteal muscle (especially the maximus) is the use of synergists. For example, weak gluteus maximus will necessitate more activity in the bicep femoris (Buckthorpe et al., 2019), creating more tension and decreased straight leg raise results upon assessment. Since the body is extremely resilient with the ability to adopt many different neuromuscular control strategies, most gluteal weakness will not demonstrate any acute symptoms during functional tasks. From my personal experience, issues typically surface chronically, but clients almost always present with pre-emptive signs.
Both bilateral and unilateral weight bearing tasks such as a squat, deadlift, or a lunge has shown to maximally activate the gluteal muscles, with any weight bearing exercise having higher MVIC % in the gluteus medius than gluteus maximus (Macadam et al., 2015). From this understanding, weakness in the gluteal muscles will either create compensation during the task, or if chronic enough, may result in an acute injury (typically in other regions of the body other than the gluteal muscles itself). For a bilateral movement, there is more support and hence, deviation patterns may start to present itself anywhere along the body, such as a rotational movement in an effort to offload the weak hip, valgus collapse of the weak OR strong hip depending on the chronicity of the weakness, increased hip flexion due to the co-activation mature of the psoas major (which may be detected by a frontal deviation of the barbell; Buckthorpe et al., 2019), pronation of the foot due to the hip’s kinetic linkage downstream, etc. For unilateral exercises, chances of errors become increasingly high due to 1) increased MVIC % of the gluteal muscles (Buckthorpe et al., 2019), 2) decreased stability compared to bilateral support. Deviations such as contralateral hip (pelvic) drop and a consequent ipsilateral trunk lean (trendelenberg), hip adduction/internal rotation due to decreased abduction/external rotation torque from the gluteal muscles, relative external tibial rotation and foot collapse, etc. All these deviation patterns will result in a decrease in strength and conditioning gains, increased injury risk, increased synergistic dominance, and decreased confidence.
Buckthorpe, M., Stride, M., & Villa, F. D. (2019). Assessing and treating gluteus maximus weakness - A clinical commentary. International Journal of Sports Physical Therapy, 14(4), 655–669.
Macadam, P., Cronin, J., & Contreras, B. (2015). An examination of the gluteal muscle activity associated with dynamic hip abduction and hip external rotation exercise: A systematic review. International Journal of Sports Physical Therapy, 10(5), 573–591.
Neto, W. K., Soares, E. G., Vieira, T. L., Aguiar, R., Chola, T. A., Sampaio, V. L., & Gama, E. F. (2020). Gluteus maximus activation during common strength and hypertrophy exercises: A Systematic Review. Journal of Sports Science & Medicine, 19(1), 195–203.