Stabbing muscles when flexed and when relaxed

Stabbing muscles when flexed and when relaxed

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Just a random question, would a sharp object pierce your muscle more(stabbed with the same amount of force) when the muscle is flexed or when relaxed?

Well, if we look in very basic detail at how muscle contraction works within a myofibril of the sarcomere:

N.b. this isn't on a loop and only plays through seven times

The red lines represent actin filaments whilst the blue lines represent myosin filaments. During muscle contraction the filaments move over each other:

As shown in the above diagrams the "more contracted" a muscle is then the smaller the size of the H zone (the area where there are just myosin filaments).

So if we consider a penetrating impact that went through a plethora of identically aligned sarcomeres (obviously this is not the case in nature) then we could presume that (et ceteris paribus) the object would not penetrate as deeply into a contracted muscle as it will hit more tissue on its route than in a relaxed muscle.

Abdominal examination

An abdominal examination is a portion of the physical examination which a physician or nurse uses to clinically observe the abdomen of a patient for signs of disease. The physical examination typically occurs after a thorough medical history is taken, that is, after the physician asks the patient the course of their symptoms. The abdominal examination is conventionally split into four different stages: first, inspection of the patient and the visible characteristics of their abdomen. Auscultation (listening) of the abdomen with a stethoscope. Palpation of the patient's abdomen. Finally, percussion (tapping) of the patient's abdomen and abdominal organs. [1] Depending on the need to test for specific diseases such as ascites, special tests may be performed as a part of the physical examination. [2] An abdominal examination may be performed because the physician suspects a disease of the organs inside the abdominal cavity (including the liver, spleen, large or small intestines), or simply as a part of a complete physical examination for other conditions. In a complete physical examination, the abdominal exam classically follows the respiratory examination and cardiovascular examination. [3]

The information gathered from the physical examination of the abdomen, along with the information from the history, are used by the physician to generate a differential diagnosis and ultimately a treatment plan for the patient.

What is happening when I flex a muscle?

Muscles anchor on bones or other muscles, and contract to produce movement. But what is going on when there is no movement, like when I flex my biceps for an awe-inspired girl? Are countervailing muscles being contracted to produce a stalemate, or I can expand a muscle without contracting it?

  • Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China
  • Posts: 256

When you contract your biceps without any movement, the triceps muscle on the opposite surface of the arm is also contracting in order to hold the elbow joint in place. It's easy to verify this by "flexing" your biceps (to an anatomist, joints flex and extend, whereas muscles only contract and relax) and placing the fingers of your opposite hand on your triceps as you do so. You should feel the triceps stiffen, indicating that contraction is taking place. Now try bending your elbow to move your hand towards your shoulder. The biceps contracts, but the triceps remains soft.

I would recommend performing these experiments without an audience, female or otherwise, or they might be more perplexed than awe-inspired.


Now let's put that 2-Channel Muscle SpikerBox to use by investigating our favorite antagonistic pair.

    Place two of your sticker electrode patches on your biceps and connect the 2 red alligator clips from channel 1 (the right side of the device) to the metal nub of the electrodes. Then place two electrode stickers on your triceps and connect the channel 2 red cables to them. Finally, place one sticker electrode on the back of your hand and connect both black alligator clips (from ch1 & ch2) to this electrode.

Alternatively, you can connect the second audio jack to your smartphone (with the green cable) and open the Backyard Brains app. Free for download for: Android or iPhone. Note that both signals will be displayed together with the current app.

A) Let's start with waving. Can you get someone to wave back at you? Which muscles do you think you are using to perform this action? To investigate your hypothesis, create an experiment by changing the placement of your sticker electrodes until you observe an EMG full of action potentials. Remember be a good scientist by documenting your method and collecting data!

B) The antagonist muscle might show spiking as well, why do you think? Try to explore your arm motions until you can completely relax the antagonist (no spikes).

Here are our results (biceps EMG is in orange above, triceps EMG is in yellow below):

Further experimentation suggestions:

Can you think of other antagonistic pairs in your body? Test out your hypothesis by recording EMGs from those two muscles to see if you are right. Remember, one should show lots of spikes (agonist) while the other shows few or none at all (antagonist) and vis versa. Another fun exploration would be to try and find two muscles that display action potentials in their EMGs even when you are standing or sitting still. The 2-Channel Muscle SpikerBox can also let you compare your muscles to your friends'. Observe your EMGs while arm wrestling!

Clinical Significance

Absent stretch reflexes indicate a lesion in the reflex arc itself. Associated symptoms and signs usually make localization possible:

Peripheral neuropathy is today the most common cause of absent reflexes. The causes include diseases such as diabetes, alcoholism, amyloidosis, uremia vitamin deficiencies such as pellagra, beriberi, pernicious anemia remote cancer toxins including lead, arsenic, isoniazid, vincristine, diphenylhydantoin. Neuropathies can be predominantly sensory, motor, or mixed and therefore can affect any or all components of the reflex arc (see Adams and Asbury, 1970, for a good discussion). Muscle diseases do not produce a disturbance of the stretch reflex unless the muscle is rendered too weak to contract. This occasionally occurs in diseases such as polymyositis and muscular dystrophy.

Hyperactive stretch reflexes are seen when there is interruption of the cortical supply to the lower motor neuron, an "upper motor neuron lesion." The interruption can be anywhere above the segment of the reflex arc. Analysis of associated findings enables localization of the lesion.

The stretch reflexes can provide excellent clues to the level of lesions along the neuraxis. Table 72.1 lists the segmental innervation of the common stretch reflexes. For example, if the biceps and brachioradialis reflexes are normal, the triceps absent, and all lower reflexes (finger jerk, knee jerk, ankle jerk) hyperactive, the lesion would be located at the C6� level, the level of the triceps reflex. The reflex arcs above (biceps, brachioradialis, jaw jerk) are functioning normally, while the lower reflexes give evidence of absence of upper motor neuron innervation.

Table 72.1

Segmental Innervation of Stretch Reflexes.

The laterality of reflexes is also helpful. For example, if all the reflexes on the left side of the body are hyperactive and those on the right side are normal, then a lesion is interrupting the corticospinal pathways to that side somewhere above the level of the highest reflex that is hyperactive.

Individual nerve and root lesions can be identified by using information about the reflexes along with sensory and motor findings. Aids to the Investigation of Peripheral Nerve Injuries is a valuable pamphlet to carry in your bag to help in testing and analyzing muscles with respect to their innervation.

Stabbing bicep pain when I lift my arm

For the last 3 months (since April 2005), I've developed a stabbing pain in my left bicep when my arm is in certain positions. The pain is located deep within my arm in the center of my upper arm and is very intense (i.e., level 8-10) as if a knife was plunged into the center of my bicep. When the pain happens, I have to use my right arm to pick up the left arm and move it into a neutral position down and in front of me. Depending on how intense the episode was, it can take anywhere from 5-10 seconds for the pain to subside and disappear completely.

The pain happens when I lift my arm into certain positions (i.e., overhead presses especially when my arm lifts next to my head or behind my head). I am no longer able to put a bar behind my neck and grip it from behind. The motion of bringing my arm up and back to grasp the bar is excrutiating. It doesn't matter if I'm lifting weights or not -- I experience the pain in my everyday life too whenever my arm is raised, bent at the elbow, and moved backward. Note, I am able to do bicep curls or hammer curls with 5# weights without pain so any bicep-related activity in front of my body is pain free. Tricep kick backs and tricep "push ups" are also pain free.

I have been active, including aerobics, biking, skiing, lifting weights (5# or less), on and off all my life and 3-4 times a week since late last year and consider myself in excellent shape and am of a normal weight for my height and age (45).

Note, I broke my ankle in June so didn't exercise much at all for 2 months but the arm pain is still there.

Outlook / Prognosis

What can I expect if I’ve been diagnosed with muscle spasms?

Muscle spasms can worsen and happen more frequently with age. Be sure to use prevention and treatment techniques to increase your chances of being able to manage the muscle spasms.

How do I take care of myself?

You and your healthcare provider should come up with a treatment plan together. Have a prevention plan and a plan for what to do when a muscle spasm hits. Do the following every day:

  • Exercise (but not in intense heat). If you get nocturnal leg cramps, do some walking before you go to sleep.
  • Stretch. Stretch frequently including before and after you exercise and before you go to sleep.
  • Purchase sturdy shoes.
  • Drink plenty of water each day. Stay away from caffeine and alcohol.
  • Take all prescribed vitamins and medications such as muscle relaxants.
  • Prepare your bed space by keeping a heating pad and massage roller nearby.

When should I see my healthcare provider about my muscle spasms (muscle cramps)?

See your healthcare provider if the spasms are unbearably painful, happen frequently or last for a long time. Also, talk to your healthcare provider right away if you have the following symptoms in addition:

  • Significant pain.
  • Swelling or numbness in the leg.
  • Changes in the skin of your leg.
  • Waking up over and over again with leg cramps.
  • If your leg cramps are stopping you from getting enough sleep.
  • If you have fluid abnormalities or electrolyte imbalances that you’re aware of.

See your healthcare provider immediately if you’re concerned that your muscle spasms are a symptom of an underlying serious medical condition.

What questions should I ask my healthcare provider about muscle spasms?

  • Do you recommend that I see a physical therapist, sleep specialist, massage therapist or other specialist?
  • Do you think that my muscle spasms are a symptom of a disease?
  • Can you show me the best exercises I can do to stretch my muscles?
  • How can I help my child when they have a muscle spasm?
  • Can you show me the best massage techniques I can use to help with my muscle spasms?

Hernia: Symptoms, Causes, and Treatments

A hernia feels like a round lump that bulges from your stomach or groin.

According to Dr. Benjamin Wedro on MedicineNet, hernia often occurs around the abdominal region when tissue pushes through stomach muscles. However, hernia can also appear in the pelvic area on either side of your genitals, in your diaphragm, or around your belly button. 7

The most common types of hernias are:

  • Inguinal hernia. This hernia occurs in men more than women and will cause a painful bulge in the groin or scrotum.
  • Femoral hernia. A femoral hernia occurs in the floor of the abdomen near the upper leg. They occur more often in women.
  • Umbilical hernia. A bulge near the belly button is usually a sign of an umbilical hernia. They are often present at birth.
  • Hiatal hernia. When part of the stomach pushes into the esophagus, this can cause a hiatal hernia and symptoms of gastroesophageal reflux disease (GERD).

Symptoms of a hernia

You know that you have a hernia because you will more than likely have a bulge in your abdominal area or pelvis.

According to Dr. Melinda Ratini on WebMD, inguinal, femoral, umbilical, and incisional hernias will cause a bulge that may disappear when you lie down. The symptoms of a hernia include a heavy, pressing feeling in the abdomen and you may have constipation or blood in your stool. 8

Not all hernias cause pain. Some are completely painless or just cause a mild ache. However, hernia isn’t tender to touch and you may be able to push the lump back into your stomach.

Abdominal hernia of the diaphragm like hiatal hernia can cause symptoms like heartburn or pain in your upper abdominal area. This type of hernia doesn’t cause a bulge but will be observable if a doctor checks your esophagus with an endoscope.

Causes of hernias

Hernias are generally caused by excess pressure in your abdominal cavity. Dr. Jerry Balentine on eMedicnineNet says that hernias can run in families and increase your risk of developing a hernia. Any weakness in the walls of your stomach muscles or abdominal cavity can cause a tissue mass to break through and create a bulge on your stomach. 9

Dr. Balentine says that other contributing factors that can cause hernias are:

  • being overweight
  • lifting heavy objects
  • persistent coughing or sneezing
  • straining excessively during a bowel movement
  • chronic lung disease
  • fluid in the abdominal cavity

How to treat a hernia

According to Dr. Balentine, most doctors recommend a “wait and see” approach and may recommend some support trusses or supporting belts. However, all hernias should be repaired surgically to prevent further complications. Even if the hernia can be pushed back into the abdominal cavity, there is always the risk that it will reappear. 10

How to prevent a hernia

Dr. Gregory Thompson on WebMD says that most hernias can’t be prevented. However, there are many steps that you can take to reduce your risk of a hernia. For example, losing weight, enjoying a healthy diet with plenty of fiber, stopping smoking, and making sure to lift heavy items properly. 11

Does muscle make you more resistant to piercing wounds (shot, stabbed)? Does fat?

Hypothetically, if we lined up a muscular person, an obese person, and a typical person, and had them shot in the same place, let's say abdomen, who would suffer less damage/trauma? Would it be different if they were stabbed?

Doesn't entirely answer the question, but the MythBusters kind of did it:

Human fat is bulletproof.

Determining that the largest layer of fat around a human (Walter Hudson) would measure 16 inches, Adam and Jamie placed that amount of human-temperature cow fat in front of the dummy. The bullet made it all the way through the fat easily.

Human muscle is bulletproof.

Using the measurements of a man with 3-inch pectorals and 11-inch biceps, Adam and Jamie placed 14 inches of cow muscle in front of the dummy (assuming the man placed his bicep over his pectoral and the bullet passed through them both). The muscle failed to stop the bullet.

Wouldn't there be a difference between a tensed up muscle and just. dead meat?

This would depend strongly on the type of bullet used. A frangible bullet, for example, will definitely not make it through 14 inches of muscle and probably not fat either. It's definitely not black and white like they are showing. Hollow points penetrate less than full metal jacket bullets. Smaller/faster calibers will penetrate less than larger/slower bullets, as the energy of very high speed bullets can literally tear the bullet apart into smaller pieces. There have been studies showing that large assailants are more difficult to incapacitate with a single handgun bullet. If you use an elephant rifle, though, it'll probably shoot through any human assailant of any size just about equally well.

Did they measure the speed or energy remaining after the penetration? That could make a big difference in damaging internal organs.

So I'm guessing it wouldn't protect against stab wounds either depending on the length of the blade?

Itɽ be nice if they mentioned what they were firing. I'm sure a full metal jacket .308 can go through a lot of meat, but a 9mm hollow point shouldn't.

It's kind of a silly question to begin with. Bullets/firearms are designed to pierce flesh. That's the whole point. Of course muscle and fat won't stop a bullet any more than road will stop a car.

They were shooting through slack muscle. If they were shooting through rock hard flexed muscle of someone huge, like Mac from always sunny, it would have not gone farther than half an inch.

Gladiators would eat a lot to build up a layer of fat to protect them from wounds that would damage their nerves or blood vessels (Source). No idea if it how effective it would be though.

This works better against a blade, which has a very definite limit on its penetration (can't go past the hilt), and against slashing injuries, which tend to be much shallower.

I think being fat would greatly help in the majority of knife wounds.

My brother is a doctor in the army and spent some time training in Texas. He told me that the hospital had seen tons of knife stabbing cases where the victim had a large enough layer of fat that the knife failed to penetrate any organs or anything vital. A quick sterilization and stitch up and they were good to go.

I believe they called it "San Antonio Body Armor."

This is sometimes true but very obese people are more difficult cases for trauma surgeons and tend to have poorer outcomes.

With being shot, iɽ say there would probably be no noticeable difference. There is something to consider about placement of the wound though. While you can make your abs larger, really the hypertrophy there is limited compared to say, your chest or arms. If you were to get shot in the chest while guarding, having large amounts of muscle and bone to go through might help some.

as far as stabbing goes, iɽ say it would have to depend on how sharp your knife is and how long it is. If you have a really obese person, and a regular pocket knife, there's a good chance that it might just hit fat and maybe some muscle rather than damaging any organs. If the knife isn't very sharp, then iɽ give the edge to the muscular person, because tense muscle is not the easiest thing to cut through. If its a razor, probably only the length of the knife and the width of the fat would make much of a difference.

tldr Fat is easier to a lot cut through than muscle, but depending on the length and sharpness of the blade the damage may favor one or the other. Getting shot is bad news either way if you hit the abdomen.

Backward tipped pelvis

The opposite of a forward tipped pelvis, a backward tipped pelvis is the least common of the four primary postural dysfunctions behind back muscle pain. It’s most frequently found in the older population.

Tight muscles:

Weak muscles:

The Neuroscience of Calming a Baby

Every parent and caregiver knows from first-hand experience that babies calm down when they are picked up, gently rocked, and carried around the room. New research published in the journal Current Biology on April 18, 2013 shows that this is a universal phenomenon. Infants experience an automatic calming reaction when they are being carried, whether they are mouse pups or human babies.

"From humans to mice, mammalian infants become calm and relaxed when they are carried by their mother," says Kumi Kuroda of the RIKEN Brain Science Institute in Saitama, Japan. Being held in a mother's arms is the safest place for a baby to be, and the mother can have peace of mind knowing her baby is happy, content, and relaxed. The fact that babies are neurobiologically wired to stop crying when carried is a part of our evolutionary biology that helps our species survive.

This study is the first to show that the infant calming response to carrying is a coordinated set of central, motor, and cardiac regulations that is an evolutionarily preserved aspect of mother-infant interactions, the researchers say. It also helps to have a scientific explanation for the frustration many new parents struggle with . a calm and relaxed infant will often begin crying immediately when he or she is put down. When my daughter was young, swaddling her seemed to create a compact posture and sense of security that triggered an automatic relaxation response when she was put back down and helped break this cycle.

What triggers this calming response?

Kuroda and colleagues at RIKEN determined that the calming response is mediated by the parasympathetic nervous system and a region of the brain called the cerebellum (Latin: little brain). The researchers found that the calming response was dependent on tactile inputs and proprioception. Proprioception is the ability to sense and understand body movements and keep track of your body's position in space. They also found that the parasympathetic nervous system helped lower heart rate as part of mediating the coordinated response to being carried.

Both human and mouse babies calm down and stop moving immediately after they are carried, and mouse pups stop emitting ultrasonic cries. Mouse pups also adopt the characteristic compact posture, with limbs flexed, seen in other mammals such as cats and lions.

The idea that the familiar calming dynamic was also playing out in mice occurred to Kuroda one day when she was cleaning the cages of her mouse colony in the laboratory. She says, "When I picked the pups up at the back skin very softly and swiftly as mouse mothers did, they immediately stopped moving and became compact. They appeared relaxed, but not totally floppy, and kept the limbs flexed. This calming response in mice appeared similar to me to soothing by maternal carrying in human babies."

The Role of the Cerebellum in Calmness

As an athlete, I have written extensively about the cerebellum and its role in coordinating fine-tuned muscle movements, balance, and proprioception. The cerebellum is always on guard to protect your body from danger and prepare you for 'fight-or-flight' by keeping track of everything going on in your environment.

Among many other jobs, the cerebellum has a huge responsibility to maintain your safety and physical well being. This takes a lot of brainpower and energy. Although the cerebellum is only 10% of brain volume it holds over 50% of your brain's neurons. Neuroscientists are perplexed by everything that the cerebellum does. This study offers one more valuable clue.

Scientists have known for years that the cerebellum is directly linked to a feedback loop with the vagus nerve which keeps heart rate slow and gives you grace under pressure. As adults, we can calm ourselves by practicing mindfulness and Loving-Kindness Meditation, which puts the cerebellum at peace and creates a parasympathetic response of well being. This appears to be the same response that occurs in infants when they are being carried.

Interestingly, the only time during the day that the cerebellum is allowed to let down its guard and go offline is during REM sleep when your body is paralyzed to prevent you from acting out your dreams. It makes sense that being picked up and carried would send automatic signals that allow the cerebellum to relax and create healthy vagal tone which would lower heart rates in infants.

The researchers believe that these findings could have broad implications for parenting and contribute to preventing child abuse. “This infant response reduces the maternal burden of carrying and is beneficial for both the mother and the infant," explains Kuroda. She goes on to say, “Such proper understanding of infants would reduce frustration of parents and be beneficial, because unsoothable crying is a major risk factor for child abuse.”

"A scientific understanding of this infant response will save parents from misreading the restart of crying as the intention of the infant to control the parents, as some parenting theories—such as the 'cry it out' type of strategy—suggest," Kuroda says. "Rather, this phenomenon should be interpreted as a natural consequence of the infant sensorimotor systems." If parents understand that properly, perhaps they will be less frustrated by the crying, Kuroda says. And that puts those children at lower risk of abuse.

The authors conclude that, “Although our study was done on mothers, we believe that this is not specific to moms and can be used by any primary caregiver.”

Watch the video: Δουλεύω τους μύες μου Δ-Ε-ΣΤ Δημοτικού (August 2022).