Pain

What is Pain?

This is the first part of an article series on the topic of pain. After reading these articles, you will be able to tell others that:

- There is a difference between acute and chronic pain.

- Pain is a personal experience influenced by many factors.

- Pain can be overly protective but can also learn to become less so.

In the past, it was believed that pain always equated to injury or illness. But how, then, do we explain phenomena such as phantom pain—pain in a limb that no longer exists? And why does a tiny paper cut hurt so much? You have also likely noticed bruises (an obvious minor tissue injury) that you did not feel when they occurred. If pain always follows tissue damage, how do we explain these phenomena? Today, we know that pain is far more complex than previously thought. We understand that your pain experience is always a combination of biological, psychological, and social factors.

Simply put, pain can be described as an alarm system signaling potential danger. Just as we have different types of sensors and alarms in our homes to detect possible threats, our bodies have similar mechanisms! Very simplified, the body's alarm system can be divided into sensors and a central alarm unit. The sensors detect different types of "danger signals" throughout the body and send these signals to the central alarm unit for interpretation. If the central alarm unit deems the signals sufficiently dangerous, you will feel pain.

The body's "danger sensors," nerve cells called nociceptors, are primarily activated by three types of stimuli:

1. Mechanical (e.g., stretch or pressure)

2. Temperature (high or low)

3. Chemical (e.g., high or low pH levels)

For example, if you stretch a ligament or muscle, this first provides a mechanical stimulus. This contributes to the pain you feel immediately at the moment of injury. A few minutes later, swelling and inflammation around the injury site will cause a chemical stimulus that contributes to the pain felt later.

Just as smoke detectors (hopefully) beep before there is a fire, the body signals danger (via pain) before damage occurs. But just as fire alarms can give "false" alarms, the body's pain system can do the same. Learn more about this in the upcoming articles.

Before you continue reading, a good starting point may be to check what you already know about pain. You can do this by completing the following sentence with as many suggestions as possible: "Pain is..."

Acute pain is often very useful and can serve a vital alarm function. This type of pain lasts from a few minutes up to three months. It is obvious that acute pain sometimes signals injury or illness. For example, acute pain that occurs after twisting your knee on the playing field can be a warning of a serious ligament injury. Pain can also be a (life-saving) symptom of acute disease in internal organs.

Most of the time, acute pain is fortunately transient and related to everyday situations. Acute pain acts as a practical and preventive alarm when your hand meets water that's too hot under the tap or when you step on a Lego brick with your foot. Experiencing entirely normal back pain is just as common. The pain informs your consciousness that "if you continue to subject your body to this, you risk injury.” In the same way, yellow warning lights in a car light up well in advance of any damage.

Note: It is always wise to check what the warning light means before driving on, even in a figurative sense.

The body has an unconscious monitoring and defense system—a collaboration between the nervous system, hormonal system, and immune system. Pain is like an alarm in this system. Acute pain can also be like the red warning lights in a car.

Simplified, the body’s monitoring and defense system can be explained by three types of sensors, a central control unit, and the warning light or alarm. Sensors detect danger in the body and send messages about this via "danger signals" to the central control unit. In the body, the brain acts as the central control unit, interpreting the signals. If the brain assesses the signals as sufficiently dangerous, pain will occur (the alarm sounds or the warning light illuminates).

The body's "danger sensors" are specialized nerve cells called nociceptors. They are activated by three different stimuli:

1. Mechanical: (e.g., stretch or pressure)

2. Temperature: (high or low)

3. Chemical: (e.g., high or low pH levels)

Example: If you stretch a ligament or muscle, the brain is first alerted by danger signals from nerve cells detecting mechanical stimuli. This contributes to the pain you feel at the moment of injury. After a while, swelling and inflammation around the injury site will cause the brain to start receiving danger signals from nerve cells detecting chemical changes.

Acute Pain Related to Injury

Acute pain related to an injury can persist for many weeks or months, concurrently with the body's natural healing process. Unlike a car or a smoke detector, the sensors in the body can adjust the threshold for how much stimulus is needed to send a "danger signal" to the brain. If the sensors monitoring the engine temperature lowered their threshold from 90 degrees to 50 degrees, warning lights would come on during every drive. This happens due to a brain mechanism called neuroplasticity, which can lead to the experience of pain during each drive. This is where long-term pain problems can arise.

However, just as the threshold for the warning light appearing at 50 degrees due to neuroplasticity can be reversed, so too can this pain threshold return to normal. This is why we use the term long-term pain instead of chronic pain.

It is very useful for the body to lower the threshold for sending "danger signals" while an injury heals. This protects the tissue undergoing the healing process, making the sensors more sensitive to stimuli. This is known in medical terms as sensitization. Have you ever had sunburn and then taken a shower? When the skin has a mild irritation, even water can cause pain. This happens precisely because the sensors have adjusted their threshold, and harmless water triggers "danger signals."

In some cases, this threshold for "danger signals" remains low, and the pain persists despite the injury or irritation being gone. You can read more about this in the article on long-term pain (link).

You should always consult a doctor if you are unsure whether acute pain might be related to a serious underlying illness.

Pain is always a complex experience. Your experiences, situation, thoughts, and emotions all influence how you perceive pain. Learning about pain can help the nervous system perceive stimuli or situations differently, which can also change your pain experience.

Approximately 3 out of 10 adult Norwegians report having long-term pain.

Causes of Long-Term Pain

Long-term pain can be related to an underlying illness, condition, event, or surgery. For pain linked to an underlying condition, it is recommended to learn more about that specific condition. For example, you can read more about osteoarthritis here (link).

Research has shown that long-term pain can also exist without being associated with any underlying illness. Pain can be a condition in itself. Complex changes in the nervous system's function can cause long-term pain to become an overly protective alarm. It is like an alarm that keeps ringing after the fire has been extinguished or a warning light that continues to blink after the problem has been fixed.

The body's sensors can become more sensitive. One of the changes that can occur in the nervous system is that the body's sensors (read more about sensors here) continue to monitor with a lower threshold than normal. This increased sensitivity means that the sensors send danger signals despite the stimuli (mechanical, chemical, or temperature) not posing a real threat. This maladaptive adjustment can be compared to a smoke detector that goes off due to steam or a warning light that blinks just because you start the car engine.

Sensor nerve cells are connected to the brain via the spinal cord. Changes can occur here too, making pain like an overly protective alarm. Usually, the body can dampen danger signals before they reach the alarm center in the brain. This happens, for example, when you blow on a scraped knee to relieve the pain. In the case of long-term pain, the body's ability to dampen danger signals through this mechanism may be reduced.

It is important to note that the brain does not have a specific "pain center," unlike centers for hearing or vision. When the brain decides whether to feel pain, various centers or departments are involved. Imagine the brain holding a "general meeting" when conducting a threat assessment. To make the best decision, all available information is gathered, including past experiences, thoughts, emotions, environmental context, and any danger signals from the body's sensors. Based on this, the brain decides whether to feel pain or not. Usually, the "pain meeting" evaluates the significance of danger signals entering the spinal cord, but not always. At the extreme, the brain's "pain meeting" can be convinced that the body is threatened even with few or no danger signals from the spinal cord. In these instances, normal joint movement or light touch to a skin area can trigger the pain alarm.

In summary, long-term pain can be caused by the brain being bombarded with danger signals due to increased sensitivity among the body's sensors, and/or the alarm center itself misinterpreting information and thus acting overly protective. Additionally, the body's ability to dampen danger signals may be reduced. This phenomenon is related to the nervous system's and cells' capacity for learning and adaptation, known as neuroplasticity. One could say that the body has "learned" to produce pain, even when it is not necessary.

What Can You Do to Reduce Long-Term Pain?

The body's and the nervous system's ability to constantly learn and adapt can both contribute to and help alleviate long-term pain. The fact that many different factors influence the pain experience also means there are many potential factors to target for reducing pain. In part 4 of this article series on pain, you can read more about the importance of physical activity for pain reduction and self-management.

Neuroplasticity

The nervous system is constantly changing to adapt to changes in our body and environment. This process is called neuroplasticity. Neuroplasticity is beneficial when it helps you become more precise in movements, block out traffic noise, or automate daily tasks like locking the front door without thinking about it.

Neuroplasticity is also crucial when a young life learns what is dangerous and what is not. The pain-related nervous system is highly adaptable to ensure that the pain's function as an alarm does not take an unnecessarily long time to learn which situations are dangerous. For example, compare the number of repetitions required for a child to learn to coordinate movements with the number of experiences needed for a child to understand that a hot stove is dangerous.

Although maladaptive neuroplasticity can cause pain to become overly protective, neuroplasticity can also help the pain alarm become less protective.

Why is Physical Activity Important?

Physical activity helps maintain muscle, skeletal, and physical functioning. When you are physically active, your body releases many beneficial substances. These substances can help with pain relief, and they can also reduce stress and muscle tension, improve sleep quality, and enhance mood. Unlike painkillers, which only reduce pain, physical activity offers a multitude of other health benefits. You could say that physical activity helps you unlock and utilize your body's natural medicine cabinet! Therefore, physical activity is a crucial part of pain management, whether you have long-term pain or are rehabilitating after an acute injury or surgery.

Strength training as a method is particularly effective on a systemic level, impacting the entire body beneficially. Some areas positively affected by strength training include:

-Cardiovascular disease

- Dementia

- Sleep

- Bone health

- Muscle mass

- Connective tissue

- Tendons

- Depression

- Cancer

• Metabolic diseases

It's like a wonder drug that's hard for some to swallow.

Which Activity Should You Choose?

The type of activity and exercise you should engage in depends on the type of discomfort you have. For example, if you have recently undergone surgery or have specific muscle, tendon, or joint issues, several exercises and training protocols are recommended as a crucial part of rehabilitation.

If you suffer from long-term pain (read more about long-term pain here), it can be more challenging to find the right type of activity. Additionally, it can be tough to find the right balance between load, frequency, and rest. Therefore, it's essential that exercise and physical activity are tailored to you, your level, and your needs. This is true for everyone and all physical activities, but perhaps even more so for long-term pain sufferers. Furthermore, the physical activity should be enjoyable and closely aligned with your own goals and functional objectives. In other words, if you have a strong desire to go on a particular hike this summer, that might be the best activity for you! But to safely and happily reach the mountain top, you need good planning and gradual training, similar to how professional climbers prepare their bodies to summit Mount Everest.

Coping with Pain During Physical Activity

The tissue in the painful area is often sensitized, and avoiding pain entirely can actually make it worse. This might seem counterintuitive, but moving with a little pain can reduce fear and desensitize the area, leading to less pain.

How to Adapt Training Along the Way

Since pain perception is individual, it can be practical to use a numerical rating scale (NRS) from 0-10 to monitor discomfort. On this scale:

- 1-4 is considered a "safe zone."

- 4-7 is the zone where most changes occur.

- Above 7, the risk of increased, persistent discomfort is greater.

It's always a balance with no exact answers, but operating within the 0-7 range is generally safe.

How to Increase Activity Levels Without Increasing Pain

Once you have determined which activities or exercises to do, the next step is to gradually increase the load or amount of activity. This means creating a gradual progression. Over time, this progression stimulates the body to adapt, similar to how you expose your skin gradually to avoid sunburn. Finding the right balance between increased load and rest is challenging and often requires trial and error.

For long-term pain, where the nervous system may have become overprotective, the right dose of physical activity can help teach the nervous system to become less protective again. While this might sound "simple," it isn't always straightforward in practice. I hope these articles can assist you in your situation, and feel free to contact a physiotherapist or other healthcare professionals if you need further guidance.