Gluteus maximus inhibition in proximal hamstring tendinopathy, by De Jesus, Bryk, Moreira, Nakaoka, Dos Reis, & Lucar, in Medical Express (2015)
The gluteus maximus originates on the posterior quarter of the iliac crest, the posterior surface of the sacrum and coccyx and the fascia of the lumbar spine. It inserts on the oblique ridge on the lateral surface of the greater trochanter of the femur and the iliotibial band of the fascia latae. In humans, the gluteus maximus is much larger than in other apes, particularly in respect of the upper region. Additionally, it is attached to the iliac crest as well as the ischium, which is not the case in other apes. Also, in other apes, the gluteus maximus is subdivided into two separate muscles whereas in humans it is a single muscle, albeit with multiple subdivisions. Indeed, the gluteus maximus contains 3 divisions from top to bottom (superior, middle, inferior) and two halves from side to side (medial and lateral) that can be shown to perform distinctly different functions in 6 regions, as can be shown by both muscle architecture and electromyography (EMG) activity.
The gluteus maximus can also be subdivided into superficial, deep sacral and deep iliac layers. The gluteus maximus is an extremely important muscle and is the largest and heaviest of all the muscles in the body. It comprises around 13 – 15% of total leg muscle mass by weight (around 600g in elderly males). It has a physiological cross-sectional area of ~34cm2 and an anatomical cross-sectional area of ~ 48.4cm2. The muscle architecture of the gluteus maximus is extraordinary in that it has both a long fascicle length and a large cross-sectional area. It is also strongly pennate, as might be expected from its large cross-sectional area. The gluteus maximus is 52 – 68% percent type I fibers, making it an evenly mixed slow and fast twitch muscle. It has its most significant moment arm in the sagittal plane for hip extension but also has a large moment arm in the transverse plane for external rotation. It also has a very small adduction moment arm in the frontal plane. Our current understanding based on anatomy, muscle architecture and EMG studies indicates that the gluteus maximus performs a number of different hip actions from extension, to external rotation and abduction/adduction. It also raises the trunk when the femur is fixed in position, and posteriorly tilts the pelvis. The gluteus maximus therefore requires a range of different movements performed with these actions in mind in order to target it fully. Various pathologies have been associated with gluteus maximus weakness. A weak gluteus maximus has been associated with an increased risk of lower back pain, excessive anterior pelvic tilt, sacroiliac joint pain, piriformis syndrome, anterior femoral hip glide, knee valgus and increased ACL injury risk and hip internal rotation and consequent foot pronation.
OBJECTIVE: To identify whether there is loss of hip extension strength (as measured by reference to maximum isometric hip extension force production by using handheld dynamometry) in the ipsilateral gluteus maximus in cases of proximal hamstring tendinopathy, by performing 3 case studies of subjects with proximal hamstring tendinopathy.
POPULATION: 3 recreationally active individuals (occupation = computer-based work) with proximal hamstring tendinopathy, being 1 male (aged 48 years, height 175cm, bodyweight 72kg), 1 male (aged 35 years, height 180cm, bodyweight 88kg) and 1 female (aged 51 years, height 159cm and bodyweight 65kg). Subjects were included where they had a diagnosis of proximal hamstring tendinopathy, and where they had undergone conservative treatment and yet achieved poor results, and who displayed a loss of muscle in the ipsilateral versus the contralateral gluteus maximus muscle.
The researchers found that there was was a reduction of hip extension force of 34% between the ipsilateral and the contralateral gluteus maximus muscles, which was accompanied by a visible loss of muscle on the ipsilateral side.
What did the researchers conclude?
The researchers concluded that individuals who display proximal hamstring tendinopathy can also present with a loss of hip extension strength and accompanying loss of gluteus maximus muscle size.
The study was limited in that the researchers did not perform a valid or reliable measurement of voluntary activation to assess whether the loss of strength was purely related to a loss of muscle mass or whether there was a neural component. Also, the researchers did not perform a measurement of the muscle size of the two sides of the gluteus maximus. Finally, the study was a case series and not a cross-sectional study with a formal study design.