How Muscle Atrophy Affects Posture & Performance
More people are sitting at desks today than ever before; and as assumed, these same individuals leave work, drive home (sitting) and sit in front of a TV or computer in their homes. More people are engaged in a sedentary lifestyle that is composed of prolonged static positions (seated or standing); and spend less time moving or exercising due to advances in technology.
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or cast for several weeks (depending on the type of fracture and bone involved), the muscles surrounding that bone are no longer active.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. This can lead to muscle atrophy and reduction in functional movement.
Sitting and Lower Back Pain
With most sedentary individuals, lower back pain is a common association with inactivity and prolonged sitting. Lower back pain that is categorised as mechanical and therefore not an injury, it 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 hernia 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. The gluteals ( your bum muscles) 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.
Function & Characteristics of the Gluteals
The gluteals muscles are involved in extending and outwardly rotating the hip, and extending the trunk. They provide 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.
How can this affect posture?
Sway back posture (1st image on the left) The sway back posture places excessive strain on the low lumbar or lower spine which becomes problematic with extension. This is often seen in those that are seated for long periods of time, that exhibit pain upon standing still. This is because the line of gravity drops behind the hip joint producing passive hip extension via body weight. This passive hip extension renders active extension from the gluteus maximus unnecessary and it ‘switches off’; the hamstring muscles, however, maintain activation to control postural sway.
Gluteal atrophy is often seen in those with sway back posture, and this can be a result of the “flattening” of the lumbar spine causing compression or herniation of the vertebra discs. Cosmetically, it is unsightly for those desiring a more “rounded” rear. Flat back posture (middle image) is somewhat similar to sway back posture. It is characterised as a malformation in which the individual has a decreased curve in the low back region.
Optimal Performance & Function Affected
Optimal posture allows the body to move more efficiently, fatigue less easily, and place less stress on the joints. Optimal posture will assist in the prevention of overtraining, muscle imbalances, and decreased performance. In the world of ‘average Joe’s’, optimal posture will decrease the likelihood of cumulative injury due to static positions. Typically, when an injury presents itself in a sedentary individual, it is the symptom of a problem—and not directly related to the site of pain. Posture helps determine which muscles are strong and weak by lengthening or shortening certain muscles. There is an optimum length at which the muscle is capable of developing maximal tension.
In order to reverse the degeneration of the gluteal muscles, loaded activity should be introduced regularly. Immobilisation studies (study used bed rest) in humans suggest that most of lost muscle and strength can be regained with appropriate resistance training several weeks after a period of disuse. From a functional performance standpoint, a basic program to isolate the gluteals with specific exercises and then integrate them into functional movements is key.
Poor lifting habits are born through mechanical disadvantages and invalid instruction. Both can be a result of one or the other. For instance, most indoor cyclists demonstrate enormous quadriceps development and hip flexor action. This popular fitness activity demands resisted knee flexion in a high stressful hip flexion position. The seated position also exacerbates the inactivity of the gluteals during a class, and reinforces the degeneration of this muscle.
Most participants will attest that a typical indoor cycling class also involves simulated hill jumps, whereas the buttocks are raised off the seat, which may involve the gluteals to some degree. Even so, the neural programming shuts off the gluteals simply because it cannot “undo” itself to fulfill an activity that supposedly involves its potential action in such a short time period.
Research shows that an emphasis on contraction of the glutes aids in stabilising the pelvis and ensures a safe and effective movement to occur. Exercises that assist this occurrence are: deadlifts, Romanian deadlifts, squats, split squats, stationary lunges, and step-ups. However, most typical exercisers resort to leg extensions, seated leg curls, leg presses, and adductors/abductors; furthering the “shut down” process.
Injury
It has been shown that injuries or pain also contribute to gluteal dysfunction or atrophy. In one study, patients who had suffered ankle sprains were shown to have a reduced activation level of the glute maximus. This may be caused by the damage to the proprioceptive feedback mechanism via lateral ankle sprain. These findings confirm that changes in muscle firing patterns, particularly by the gluteus maximus, can lead to muscle inhibition and/or atrophy. This compromise could result in a compensation of the lower back. A situation where an injury has likely occurred and has altered the normal function of the human body (gait, running, sitting, getting in or out of a car, etc), should emphasise the importance of corrective exercise and rehabilitation.
Most individuals that do not receive proper rehabilitation for such injuries like ankle sprains develop scar tissue and immobilisation of the ankle joint that further exacerbates atrophy of the gluteals. Most basketball players that experience low back pain have a history of ankle sprains that have altered the function of the glutes, which become more important for the taller athlete because of the longer limbs creating a “longer lever” stress on the back.
Summary
The importance of gluteal function is imperative to proper posture and human performance. Without optimal function from the glutes, sedentary individuals may exhibit low back pain and other associated injuries. In severe cases, the gluteal muscles fail to absorb the shock impact in the load transfer during walking, which studies have shown to lead to some forms of hip osteoarthritis.
What types of modifications to daily lifestyle can sedentary people begin to do to combat the effects of gluteal atrophy?
Move more – According to Stuart McGill, PhD in his book, “Low Back Disorders”, moving and “fidgeting” while in a seated position breaks the constant pressure placed on the body by gravity. Constantly, changing seated or standing positions alleviates low back strain and repositions the glutes.
Walk – The office worker seldom has the chance to exercise during the day. Adding some “purposeful” movement, such as fast walking, during a lunch break is important to circulating pooling blood from the lower body, burn calories, and lengthens muscles.
Take stairs – Sounds simple, yet, the act of extending the hip under the load of the body will enhance glute performance – provided it is performed without the compensatory assistance of the lumbar spine.
Stretch more – Along with moving and walking, standing from a seated position regularly allows the vertebral discs to decompress and lengthens muscles that are otherwise in the process of shortening.
Humans are meant to be upright as a species and it is the function of the gluteal muscles that allow that. As the sedentary become more and more inclined to sit, the more obvious it becomes to see the damage caused. With small modifications and changes made throughout one’s day, it is a battle that can be one in small increments through purposeful activity, and properly loaded exercises.