question: I just realized that the muscles around our necks are constantly holding up the weight of our heads for most of the day. Why don’t those muscles ever feel tired or sore?
comment: There are three types of muscle: 1. Cardiac muscle: The muscle in your heart. 2. Smooth Muscle: The muscle in your gut that pushes stuff through your bowels (and also does a few other things). 3. Skeletal muscle: Attaches to bones and helps you move around. There are three types of skeletal muscle: * Type 1: Red/slow fibers aka type 1 fibers aka slow twitch fibers. They are the postural muscles that keep you standing all day. They can't lift a lot of weight, but they don't get tired or feel sore. Your neck fibers fit into this category. * Type 2a: Red/fast fibers aka type 2a fibers aka fast oxidative fibers. They are muscles primarily used to run around and use your arms. * Type 2b: White/fast fibers aka type 2b fibers aka fast oxidative fibers. They are used to lift really heavy things or sprint, but they get tired really fast. The reason why muscles get tired is that they run out of energy. Red muscle fibers have a lot of mitochondria (the powerhouse of the cell). They can constantly turn sugar and fat into energy. They make ATP (which is the molecule that energy is stored as) faster than they lose it by holding your neck up. So they can do it all day without feeling tired or sore. Meanwhile, white fibers store a lot of energy in them, but they can't make more very fast. So they can quickly burn through a lot of energy, bu then they need to rest and refill their energy. That's why you can bench press a ton of weight in one set, but you need some time to recover afterwards.
passages: Weight lifting, if not done correctly, can be detrimental to posture, and causes a lot of the neck and shoulder problems in countless athletes. Vern Gambetta, in his article "Perfect Posture", states; "Overemphasis on the bench press can [hinder good posture], as it causes a round-shouldered posture." The rounding of the shoulders can cause pain as stated in the University of California at Berkeley Wellness Letter; November 2000, "Increase in neck and shoulder pain may be due to the postural problems in the upper body including rounded shoulders and jutting the head forward. Although the thoracic and lumbar spines are crucial factors in postural problem, they tend to overshadow the head or the cervical spine. An article in the February 2006 Consumer Reports on Health remarked that "Research has found, for example that letting your head jut forward is associated with neck, back and even jaw pain." Some headaches are the result of poor head posture. The decrease and even loss of shoulder movement along with chronic pain, neck-related headaches and the decline in the ability to exercise as well as many other problems stem from poor posture. Injuries and pain caused by poor posture span a wide variety of people. All areas of the spine are equally important when it comes to posture.
   BULLET::::- The cantilevered (poked forward) head position loads the spine up to several times more than erect posture, because of the increased moment arm. So the posterior neck muscles (especially the upper fibres of trapezius) holding the head in its forward position, often sustained for many hours, can strain, producing individual myofibril and cell damage. Repair of this microtrauma involves the laying down of adhesive fibrosis, as a normal part of the inflammatory response. Adhesive fibrosis is relatively non-elastic, so after sufficient repeated microtrauma from muscle strain, the posterior neck muscles become strained, shortened and less elastic.
   Baroreceptors are integral to the body's function: Pressure changes in the blood vessels would not be detected as quickly in the absence of baroreceptors. When baroreceptors are not working, blood pressure continues to increase, but, within an hour, the blood pressure returns to normal as other blood pressure regulatory systems take over.
  
  Baroreceptors can also become oversensitive in some people (usually the carotid baroreceptors in older males). This can lead to bradycardia, dizziness and fainting (syncope) from touching the neck (often whilst shaving). This is an important cause to exclude in men having pre-syncope or syncope symptoms.
  
  Section::::See also.
   Poor posture can stem from many sources; one of the most significant sources deals with repetitive motion without frequent breaks. If one spends a substantial part of one's day in a certain position without frequent reprieves, the spine tends to orient itself to that movement. For example, if someone is constantly leaning over to pick up objects, gradually the spine will start to develop a more exaggerated forward curve of the thoracic spine. Sullivan comments on poor posture saying; "These problems [poor posture] are often the result of chronic muscle tension, physical injuries or even emotional trauma, such as grief or depression. Conditions like these throw the musculoskeletal system out of alignment, and if not corrected, poor posture eventually feels normal." Emotions, as well as physical activities, affect the state of one's posture.
   Section::::Causes.
  
  Possible causes that lead to the condition of Lumbar hyperlordosis are the following:
  
  BULLET::::- Spines – Natural factors of how spines are formed greatly increase certain individuals' likelihood to experience a strain or sprain in their back or neck. Factors such as having more lumbar vertebrae allowing for too much flexibility, and then in cases of less lumbar the individual not reaching their necessity for flexibility and then pushing their bodies to injury.
   Poor posture
  
  Poor posture is the posture that results from certain muscles tightening up or shortening while others lengthen and become weak which often occurs as a result of one's daily activities. There are different factors which can impact on posture and they include occupational activities and biomechanical factors such as force and repetition. Risk factors for poor posture also include psychosocial factors such as job stress and strain. Workers who have higher job stress are more likely to develop neck and shoulder symptoms.
  
  Section::::Types.
  
  Poor posture can present in several ways:
   A peer-reviewed 2007 study with Schechter, Smith and Stanley Azen, Professor and Co-Director of Biostatistics in the Department of Preventative Medicine at the USC Keck School of Medicine, found a 54% success rate for treatment of TMS ("P".00001). The treatment consisted of office visits, at-home educational materials, writing about emotional issues and psychotherapy. The average pain duration for the study's patients was 9 years. Patients with less than 6 months of back pain were excluded to "control for the confounder that most back pain episodes typically resolve on their own in a few weeks."
   It is suspected that "H. sapiens" ancestors’ did not initially forage on the forest floor; instead they migrated from the trees for various reasons. In that environment, they survived on a diet high in plant matter with some insects and little amounts of meat. They were not very formidable opponents to more dominant mammals such as large ancient cats (lions, leopards) but their ability to be better hunters and gatherers along with their corresponding brain development, gave them the advantage to add high-calorie nutrient supplies such as meat to their diet. Analysis of the jaws and skull of the supposed human ancestors show that they had larger, stronger jaw muscles attached to the skull which would be expected with a diet rich in fruit and plants. The back set of molars were much larger for this reason also. The dependence on these higher-calorie foods came from the inefficiency of bipedalism and the growing energy costs of climbing tall trees. Human ancestors are thought to have had more muscles connecting the skull, neck, and shoulders/back area (similar to apes) which caused their neck and skull regions to appear to sag, such as non-human primate species do. These diminished muscles allow the human head to be held in its current ‘upright’ position and lets the occipitofrontalis muscle, or the forehead, to function as an aid to expressions.
   Other causes include sustained immobile posture for long periods of time. Taylor, Consmüller, and Rohlmann in their article "A novel system for the dynamic assessment of back shape" in the "Medical Engineering & Physics" journal, say: "Low back pain is an increasing problem and can be aggravated by prolonged static posture. Sitting for prolonged periods is a great hindrance to good posture. Poor sitting posture is hard to rectify. Jenny Pynt in The Physiotherapy Theory & Practice journal states, "In sitting there is no one ideal posture, nor should one posture be sustained. Healthy sitting posture therefore, is best thought of as an active not static phenomenon." There are ways to improve your posture such as rolling your shoulders back and down, making sure your ears are aligned with your shoulders, and strengthening your core muscles. Poor posture is affected by prolonged periods of repeated motions, or remaining fixed in one particular position.
   Section::::Biomechanics.:Heart and metabolic stress.
   Signs of these conditions include the slow onset of discomfort and pain in the upper shoulder or upper third of the arm and/or difficulty sleeping on the shoulder, similar condition can have sharp pain or discomfort when the upper shoulder is positioned at certain angles. Tendinitis and bursitis also cause pain when the arm is lifted away from the body or overhead. If tendinitis involves the biceps tendon (the tendon located in front of the shoulder that helps bend the elbow and turn the forearm), pain will occur in the front or side of the shoulder and may travel down to the elbow and forearm. Pain may also occur when the arm is forcefully pushed upward overhead.
   Section::::Biomechanics.:Flexibility.
   The lumbar (or lower back) region is made up of five vertebrae (L1–L5), sometimes including the sacrum. In between these vertebrae are fibrocartilaginous discs, which act as cushions, preventing the vertebrae from rubbing together while at the same time protecting the spinal cord. Nerves come from and go to the spinal cord through specific openings between the vertebrae, providing the skin with sensations and messages to muscles. Stability of the spine is provided by the ligaments and muscles of the back and abdomen. Small joints called facet joints limit and direct the motion of the spine.
   Typically, fan-shaped muscles experience varying degrees of fiber strain. This is largely due to the different lengths and varying insertion points of the muscle fibers. Studies on ratfish have looked at the strain on fan-shaped muscles that have a twisted tendon. It has been found that strain becomes uniform over the face of a fan-shaped muscle with the presence of a twisted tendon.
  
  Section::::Architecture types.:Pennate.
   The head is supported by the lower neck and upper back, and it is these areas that commonly cause neck pain. The top three joints in the neck allow for most movement of the neck and head. The lower joints in the neck and those of the upper back create a supportive structure for the head to sit on. If this support system is affected adversely, then the muscles in the area will tighten, leading to neck pain.
  
  Neck pain affects about 5% of the global population as of 2010.
  
  Section::::Differential diagnosis.
   However, research on living animals has argued that most living tetrapods habitually raise the base of their necks when alert. Inference from bones about "neutral postures", which suggest a more horizontal position, may be unreliable. Research published in 2013 that studied ostrich necks, however, took the estimated flexibility of sauropod necks into doubt. Studies by Matthew Cobley et al revealed, using computer modeling, that muscle attachments and cartilage present in the neck would likely have limited the flexibility to a considerable degree. The authors cautioned against estimating range of motion from just using the bones alone. This discovery also reveals that sauropods may have had to move their whole bodies around to better access areas where they could graze and browse on vegetation.
   There are several muscles in the low back that assist with rotation, flexibility and strength. These muscles are susceptible to injury, especially while lifting heavy objects, or lifting while twisting. A low back muscle strain can be extremely painful but will usually heal within a few days or weeks.
  
  The lumbar portion of the spine bears the most body weight and also provides the most flexibility, a combination that makes it susceptible to injury and wear and tear over time. This is why low back pain is so prevalent.
  
  Section::::See also.
  
  BULLET::::- Back belts
  
  BULLET::::- Car seat and lumbar support
   Hunching increases the effective load on the neck up to several times more than does erect posture, due to increasing moment arm. Local pain, cervicogenic headache and referred pain extending down the arms can arise from the sustained muscle strain, cervical facet joint (or apophyseal, or zygapophyseal joint) compression and diminution of the cervical foraminal nerve exits.
   Section::::Contributing factors.:Work.
  
  Working on steep hills, galloping, and jumping all contribute to navicular syndrome, as they place greater stress on the DDF tendons, and may cause overextension of the pastern and coffin joints.
  
  Regular exercise on hard or irregular ground increases concussion on the hoof, thus increasing the risk of navicular syndrome.
   This chain of events can be and often is accelerated by kyphosis, which is invariably accompanied by rounded shoulders, both of which place greater stress on the QLs by shifting body weight forward, forcing the erector spinae, QLs, multifidi, and especially the levator scapulae to work harder in both seated and standing positions to maintain an erect torso and neck. The experience of "productive pain" or pleasure by a patient upon palpation of the QL is indicative of such a condition.
   Giraffes have a great effect on the trees that they feed on, delaying the growth of young trees for some years and giving "waistlines" to trees that are too tall. Feeding is at its highest during the first and last hours of daytime. Between these hours, giraffes mostly stand and ruminate. Rumination is the dominant activity during the night, when it is mostly done lying down.
  
  Section::::Behaviour and ecology.:Social life.
   On June 14, 2013, the St. Louis Rams signed McDonald to a four-year, $3.79 million contract that includes a signing bonus of $679,740. McDonald entered training camp slated as the starting free safety. Head coach Jeff Fisher named him the starting free safety to start the regular season, alongside strong safety Darian Stewart.
   Another main factor is the tension placed on the ligaments that support the navicular bone. Some experts believe that the degenerative process begins with excess tension placed on these ligaments, causing strain and inflammation. Inflammation from strain of the impar ligament can decrease blood flow to and from the navicular bone, as the major blood vessels supplying the bone run up and down this area. If the ligament continues to be strained, it can thicken and permanently reduce blood flow to the navicular bone.
   Although the musculature of the head and neck and psychological factors such as stress may play a role in the overall pathophysiology of TTH, neither is currently believed to be the sole cause of the development of TTH. The pathologic basis of TTH is most likely derived from a combination of personal factors, environmental factors, and alteration of both peripheral and central pain pathways. Peripheral pain pathways receive pain signals from pericranial (around the head) myofascial tissue (protective tissue of muscles) and alteration of this pathway likely underlies episodic tension-type headache (ETTH). In addition to these myofascial tissue pain signals, pericranial muscle tenderness, inflammation, and muscle ischemia have been postulated in headache literature to be causal factors in the peripheral pathophysiology of TTH. However, multiple studies have failed to illustrate evidence for a pathologic role of either ischemia or inflammation within the muscles. Pericranial tenderness is also not likely a peripheral causal factor for TTH, but may instead act to trigger a chronic pain cycle in which the peripheral pain response is transformed over time into a centralized pain response. It is then these prolonged alterations in the peripheral pain pathways that lead to increased excitability of the central nervous system pain pathways, resulting in the transition of episodic tension-type headache into chronic tension type headache (CTTH). Specifically, the hyperexcitability occurs in central nociceptive neurons (the trigeminal spinal nucleus, thalamus, and cerebral cortex) resulting in central sensitization, which manifests clinically as allodynia and hyperalgesia of CTTH. Additionally, CTTH patients exhibit decreased thermal and pain thresholds which further bolsters support for central sensitization occurring in CTTH.
   Moving the wrong way, such as twisting in awkward positions or improperly lifting heavy objects, can lead to painful injuries, the most common of which is a herniated disc in the spine. A herniated disc injury can cause severe pain and in some cases bowel or bladder dysfunction. Georgia’s carpet and rug mill workers are often at risk for these types of injuries because they frequently lift or lean over heavy rolls of material.
  
  Transportation Incidents:
  
presuppositions: Due to the neck carrying the head the entire day, it should eventually tire out and fail to support the head. 
corrections: Muscles in the neck are known as muscles with slow twitch fibers, while they can't lift a lot of weight, they are postural and typically can support body parts for prolonged periods of time without tiring.
raw_presuppositions: Due to the neck carrying the head the entire day, it should eventually tire out and fail to support the head.  All muscles get tired.
raw_corrections: Muscles in the neck are known as muscles with slow twitch fibers, while they can't lift a lot of weight, they are postural and typically can support body parts for prolonged periods of time without tiring. Some types of muscles can replenish energy faster than they lose it from holding your neck up, and as a result do not get tired.