Wednesday, May 18, 2011

How Glute Atrophy Effects Posture & Performance, Pt. 1

Here are some excerpts from an article I had written a few years ago that has been featured on and

Is it possible that a sedentary lifestyle, absent of purposeful loaded activity or exercise, can cause atrophy of muscles? Take the example of a broken bone. Once fractured and encased in a splint or cast for several weeks (depending on the type of fracture and bone involved), the muscles surrounding that bone are no longer active. They are not active because the “lever system” that they are associated with is impaired. Therefore, without proper muscle firing or use, the muscles lose tonus, weaken, and decrease in neural response.

Studies have been shown that unloaded inactivity induces atrophy and functional de-conditioning of skeletal muscle—especially in the lower extremities. (1) In this case, “unloaded” should be defined as absence of an external load, and “inactivity” is defined as little to no muscular movement, stimulation, or locomotion. In this particular study, ten healthy males were subjected to 5 weeks of experimental bed rest. Each participant was matched with an associate to assist in minimal tasks. Their lower body muscles were tested using isometric hip and knee extension exercises. After the 5 weeks, atrophy was more pronounced in the extensor muscles of the gluteal region, thigh, and calf. Furthermore, radiological density tests indicated a bone mineral loss already after 5 weeks.

The study’s use of bed rest as the intended unloaded inactivity is somewhat similar to the conditions a sedentary individual undergoes when the occupation calls for a majority of time seated (secretary, computer tech, call service, office worker, etc, etc). Because bed rest is an extremely inactive state, we can only assume that the seated position sustained over a number of years is just as detrimental to skeletal muscle given the amount of time (duration in years); frequency (how often), and duration (how long each time).

As with most sedentary individuals, lower back pain is a common association with inactivity and prolonged sitting. Lower back pain that is categorized as mechanical will typically involve musculoskeletal factors that may be influenced by lifestyle, activity, and body composition. Other types of low back pain are structurally specific to the spine and involve conditions such as arthritis, disc herniations, and degeneration. In mechanical low back pain, muscular length-tension relationships change over time in relation to the stress put on the body. For example, in the seated position, the hip flexors are in a constant shortened state and the knee flexors—primarily the gastrocnemius remains shortened. To exacerbate the effects of prolonged sitting, poor posture such as slouching, shoulder protraction, and cervical flexion, cause the erectors of the back to become overactive and fatigue causing the associated “creep”. 

The gluteals remain inactive in a seated position. Sitting for long periods can lead to the gluteal muscles atrophying through constant pressure and disuse. Movements that require the gluteal muscles become more difficult (such as climbing stairs or rising from a seated position); therefore, extra stress is put on the lumbar spine leading to low back pain. 

LEFT: Atrophied Glutes (White is fatness)

The gluteals are comprised of 3 muscles: glute minimus, glute maximus, and glute medius.  These muscles are involved in extending and outwardly rotating the hip, and extending the trunk. The powerful gluteus max inserts into the iliotibial band and gluteal tuberosity of the femur. Because of its attachment, it provides the human body incredible leverage and sets our species apart from other primates (upright versus four legged). Lower body exercises, such as squats, deadlifts, lunges, and good mornings, strengthen the gluteal muscles. These exercises focus on glute strengthening because there is a muscle action demand that corresponds with the muscle’s responsibility.  In a seated position, there is no demand for the muscles to act (unloaded inactivity); therefore, over the course of time, the gluteals will decrease in neural output. If there is a decrease in the “call time” of a muscle, surrounding muscles will enact to complete a movement causing muscular imbalances and stress on joints. In the case of functional performance, the lumbar spine receives the brute of this compensatory pattern.

Typically, when there is a lack of gluteal function, there is a visible lack of gluteal development in an individual. The gluteal muscles are only partially responsible for giving the buttocks their characteristic shape. The subcutaneous fat that also contributes to the “roundness” of the buttocks is called the panniculus adipose. If the gluteus musculature is atrophied and subsequently “absent” from providing shape, then the overlying panniculus adipose is responsible for the “sagging butt” appearance. This appearance is no illusion and gives credible evidence that the glutes do not function properly – by means of weakness and neural deviation.

LEFT: "Empty" looking buttocks--only panniculus fat tissue

 In Part 2 of this post,  I will go into the different causes of glute atrophy and how it effects perfromance- including what you can do to regain strength in the gluteals and retain their "roundess".


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