The Science Behind Why We Hurt

Home/Pelvic Pain/The Science Behind Why We Hurt
  • The Science Behind Why We Hurt

The Science Behind Why We Hurt

Author:  Laura Plankis PT, DPT N2 Physical Therapy at Swedish Medical Center

Pain can interfere with your life. Pain can feel suffocating as if there is no escape. It can cause you to discontinue hobbies, chores, or even your occupation.

Pain can set in randomly throughout the day or constantly aggravate you. Pain can be described as sharp, dull, achy, burning, stabbing or sometimes indescribable. So why does pain exist, and what causes it to dissipate for some and linger for others?

What is pain?The Science Behind Why We Hurt

Pain is normal, in that it acts as a temporary alarm to alert our body that we need to take action.1,2 Pain is produced by the brain when it receives information from the periphery that danger exists and action is required.3,4 In other words, pain from the hot burner of a stove is what causes you to move your hand away. Pain in your ankle following an injury is what influences you to seek out advice from a medical professional on whether it is a sprain or fracture. Pain or burning while urinating is what alerts you to see a doctor to determine if you have an infection. Pain with sitting is your pudendal nerve’s alarm to see a pelvic physical therapist to address possible dysfunction. All of these examples of pain described are transient – they may linger for a short while, but eventually fade.

Chronic pain is not normal.1,2 Chronic pain is pain that continues past the time frame of normal tissue healing and is commonly defined as pain lasting longer than 3 months.5 Chronic pain is complex and continues to be further researched every year in attempt to improve understanding of it. This blog is a small glimpse into the world of chronic pain, for further information and to gain insight into treatment seek out advice from one of our skilled physical therapists at N2 Physical Therapy.

Central Versus Peripheral

There are several different theories related to the causes of chronic pain and a variety of treatment approaches. In recent years, more and more research is surfacing that aim to join the two major theories of pain – peripheral causes of pain versus central causes of pain. Peripheral involves the tissues of your body, such as the pelvic floor musculature, whereas central refers to the spinal cord and brain. Prior to more recent research of chronic pain the common idea was that the brain received information from the periphery on the intensity and location of the pain.6 This was described simply as the thought of a telephone wire going from the tissue to the brain.6 Research now shows that the interactions between the periphery and the brain are much more complex than a telephone wire. Recent research has revealed that the brain not only receives information from the periphery, it can also change pain perception by amplifying the pain, increasing the duration of the pain, and even changing the location of the pain.6 In the sections below, the concept that peripheral causes of pain causes confusion within the spinal cord and brain will be further explored.

Peripheral Causes

n2_pain3Injury and pain are not one in the same.1,7 You may have pain but no injury, or injury but no pain.1,7 Seeing a bruise on your leg and not knowing where it came from is an example of an injury without pain.2 The bruise is visible proof that capillaries have been damaged by some sort of trauma; however pain was never present to alert you that something is wrong. The human body has incredible mechanisms to repair tissue; therefore the tissue injuries following vaginal delivery of a woman’s first child will be healed yet pain may continue for years. This is an example of pain but no injury. So what is contributing to this pain?

One answer includes extra sensitive nerves, where the nerves in the periphery start firing persistently, even in the absence of danger.1,2,7 Using the childbirth example, the initial injury would result in the nerves sending messages to the brain and the brain responding by increasing chemical substances that both cause pain and initiate the healing process. Then the nerves would stay at an elevated firing rate or excitability level while the tissue was healing to remind the body that the area is in a state of fragility. With the nerves at a higher level, less movement or stress to the tissues would be required to alert the brain of possible danger. Over time the nerves excitability level decreases to their original baseline level. However, with chronic pain the nerves never reach their baseline level.1,2,7 This means that the amount of pressure, movement, and/ or stress that the area can receive prior to alerting the brain is less than what was previously normal for that person. In other words, things that previously caused no discomfort, now cause pain. Although this example uses the starting point of an injury, it is important to remember that pain doesn’t always begin with an injury.1,7 Therefore, you can have extra sensitive nerves without an injury.


Another contributing factor to chronic pain may be myofascial trigger points. Myofascial trigger points develop as a taut band or contractured muscle fibers, activated by the spontaneous release of acetylcholine, a specific chemical formed in the human body.7,8 Myofascial trigger points can cause allodynia (pain from something that usually isn’t painful) over the trigger point and hyperalgesia (increased sensitivity to pain) of the surrounding area.7,9 Active myofascial trigger points can also cause referred pain to an area away from the trigger point.6,7,9

n2_pain5Chronic pain can also be influenced by abnormal movement patterns and postures. It may be impossible to differentiate if pain causes abnormal movement or if abnormal movement causes pain.3 Regardless, restoring pain-free movement is a key component to physical therapy treatment. When pain persists, there is increased activity of the large superficial muscles and decreased activity of the smaller stabilizing muscles within our body.1,2,3,4,7 There is also evidence to show increased co-activation of musculature leading to muscle overload.8 Research has shown that myofascial trigger points can create altered motor control strategies.7,8 This can be caused by overactivation of antagonist muscles inhibiting agonist muscles, which can further increase pain.8 In other words, during a healthy and coordinated movement pattern, the antagonist muscle should relax to allow the agonist muscle to fully contract through the movement. When trigger points are present, this muscular interaction and activation pattern may be opposite. This creates altered movement patterns and posture that may feed into additional new pain or amplify your current pain.

n2_pain6Stress is another source of continued pain and increasing pain. Cortisol is the primary stress hormone within the human body; therefore, cortisol levels increase as stress levels increase.1,2,10,11 Cortisol’s effects on tissues, such as muscles, include soreness, fatigue, sensitivity, and weakness.10 There are also nerves within the body that can be influenced by stress. For example, the pudendal nerve, which has a complex route through the pelvis and pelvic floor, is influenced by stress due to its connection with the autonomic nervous system.12,13 When treating chronic pain, addressing solutions to manage stress is a critical component of the plan of care.

Central Causes

The brain and spinal cord are involved in central causes of pain and play a major role in chronic pain.

Consider the spinal cord as the front door to the brain. The door is usually locked so that someone bringing a message of pain can not readily enter the brain. As pain fibers continue to fire towards the spinal cord, changes occur causing more of those messages to continue towards to brain.3,6,7 Going back to the example of the door, continued firing of pain causes the door to remain open without a lock. Using this example think about the clothes you wear everyday. With the door locked, you are able to go throughout the day without feeling your pants touching your skin. However, if the door remains unlocked the touch of your pants on your skin may feel more sensitive or even painful. This is an example of how central causes of pain can contribute to allodynia, or pain caused by something that usually isn’t painful.14

When pain signals reach the brain, the brain has to make a decision regarding how dangerous the threat is and then prepare the body for an action.3,4 The brain does not make this decision on one factor alone – pain is multifactorial and takes into account beliefs, stress, anxiety, fear, emotional health, lifestyle, etc. in combination with the sensory and muscle input.1,3 After all the factors are evaluated and processed, the brain then decides whether the stimulus or movement should be received as painful/ dangerous and how to react. Although pain is dictated by your brain, pain is not “in your head”.1,2,3 Pain is real, your pain is real.


Within the brain, there is no single pain center; therefore, there are multiple areas of the brain functioning and activated during pain.1,2,15 If multiple areas of the brain are involved in processing the incoming sensory and muscle input related to pain, that leaves less of the brain available to function on everyday tasks. This may help explain the reason for feeling forgetful, clumsy, weak, tired, and confused while experiencing chronic pain.3

Collaborate with a Physical Therapist (PT)

Pain is complex and varies greatly from person to person. Chronic pain can alter the sensitivity of your nerves,1,2,7 cause continued activation of myofascial trigger points,6,7,9 alter your movement and modify your posture,1,2,3,4,7,8 and even cause confusion or forgetfulness.3 Treatment was not discussed in this blog, because based on the variability involved in pain, there is likely no one treatment that will decrease pain for everyone. However, there is one thing that multiple research articles all seem to agree on when it comes to treating chronic pain: understanding pain is the first step.1,2,3,4,10 By reading this blog and learning about pain, you have taken the first step towards an appropriate treatment protocol.

n2_pain9The staff at N2 Physical Therapy are trained in a variety of advanced techniques and hold multiple speciality certifications including CMTPT (Certified Myofascial Trigger Point Therapist) and CLT – LANA (Certified Lymphedema Therapist – Lymphology Association of North America). We are skilled, compassionate, and eager to address your individual goals of therapy related to chronic pain and continue helping you increase your knowledge about your pain. Maybe you had tissue damage from childbirth and your nerves never returned to baseline. It is possible the stress of being laid off from work and financial struggles is inflaming your pudendal nerve, increasing pain. Perhaps you have a myofascial trigger point within one of the many pelvic floor muscles that is referring pain to your lower abdomen. We would love to discuss with you how the above principles described in this blog can be applied to treating your chronic pain. Call any of our three locations to schedule with a physical therapist and see how your quality of life can improve as your pain decreases.


Laura Plankis PT,DPT



  1. Louw, Adriaan. Why Do I Hurt?: A Patient Book about the Neuroscience of Pain. 1st ed. N.p.: International Spine and Pain Institute, 2013. Print.
  2. Louw, Adriaan, Sandra Hilton, and Carolyn Vandyken. Why Pelvic Pain Hurts: Neuroscience Education for Patients with Pelvic Pain. N.p.: International Spine and Pain Institute, 2014. Print.
  3. Moseley, G. L. “A Pain Neuromatrix Approach to Patients with Chronic Pain.” Manual Therapy 8.3 (2003): 130-40
  4. Reconciling Biomechanics with Pain Science. Last accessed 10/10/2016
  5. Classification of Chronic Pain. Last accessed 10/10/2016
  6. Woolf, Clifford J. “Central Sensitization: Implications for the Diagnosis and Treatment of Pain.” Pain 152.Supplement (2011): 8-21
  7. Dommerholt, Jan. “Dry Needling — Peripheral and Central Considerations.” Journal of Manual & Manipulative Therapy 19.4 (2011): 223-27.
  8. Ge, Hong-You, César Fernández-De-Las-Peñas, and Shou-Wei Yue. “Myofascial Trigger Points: Spontaneous Electrical Activity and Its Consequences for Pain Induction and Propagation.” Chinese Medicine Chin Med 6.1 (2011): 13.
  9. Mense, Siegfried. “Muscle Pain: Mechanisms and Clinical Significance.” Deutsches Arzteblatt International 105.12 (2008): 214-19
  10. Melzack, Ronald. “Pain and the Neuromatrix in the Brain.” Journal of Dental Education 65.12 (2013): 1378-82
  11. Understanding the Stress Response. Last accessed 10/10/2016
  12. Learning Modules – Medical Gross Anatomy: Autonomics of the Pelvis. Last accessed 10/10/2016
  13. Anatomy of the Pudendal Nerve. Last accessed 10/10/2016
  14. Todd, Andrew J. “Neuronal Circuitry for Pain Processing in the Dorsal Horn.” Nature reviews. Neuroscience 11.12 (2010): 823–836. PMC. Web. 12 Oct. 2016.
  15. Niddam, David M., Rai-Chi Chan, Si-Huei Lee, Tzu-Chen Yeh, and Jen-Chuen Hsieh. “Central Modulation of Pain Evoked From Myofascial Trigger Point.” The Clinical Journal of Pain 23.5 (2007): 440-48.


  1. Pain. Last accessed 10/25/2016
  2. Stove Top Pain Reflex. Last accessed 10/26/2016
  3. Pain does not equal damage. Last accessed 10/25/2016
  4. Sensitive Nerve Graph. Last accessed 10/25/2016
  5. Diagram of a Trigger Point. Last accessed 10/25/2016
  6. Stress and Pain Diagram. Last accessed 10/25/2016
  7. Chronic Pain Diagram. Last accessed 10/25/2016
  8. Pelvic Pain. Last accessed 10/25/2016
Comments Off on The Science Behind Why We Hurt

About the Author:

Laura Plankis, DPT
Laura received her Doctorate of Physical Therapy at Chatham University in Pittsburgh.

She focuses her practice on women’s health and pelvic health, and enjoys treating the patient as a whole and incorporating a balance of manual treatments and therapeutic exercises.

Location: N2 Physical Therapy at Swedish Medical Center