Exercises prescribed during rehabilitation are
non-pharmacological ways to reduce pain, increase muscle activation, and muscle
adaptation to different loading. Regular physical activity helps restore or
prevent chronic pain conditions. Studies have determined that regular
exercise decreases exercise-induced pain, and acute bouts of exercise
may help. This article delves deeper into exercise-induced hypoalgesia in the long and short
Exercise-induced hypoalgesia is a mechanism that increases tolerance to pain.
Pain-inhibitory response immediately following an acute bout of exercise is small and not for chronic disease conditions.
Regular and long-term physical activity and exercises help to increase tolerance to pain in the general population compared with a sedentary lifestyle.
Tolerance to pain increases when people start to increase their physical activity level from light to moderate or vigorous, but not vice versa.
Different types of exercises can enhance endurance, muscle force, muscle recruitment, balance, coordination, agility, mobility, and stability. Overall, exercise positively affects our health and quality of life, including cardiovascular health, mood, sleep, and coping with stress.
After every intervention related to our body, surgery, injury, or other medical conditions that connect with the musculoskeletal system goes together with rehabilitation that mainly consists of physical exercises with different and progressively increasing loading to increase the amplitude of movement, muscle force, postural control, and balance.
Many studies analyze how physical exercise can help reduce chronic pain and the fear of moving. More and more studies analyze exercise-induced hypoalgesia.
What is exercise-induced hypoalgesia?
Exercise-induced hypoalgesia mechanism is not fully understood. However, the mechanism responsible for this effect is the endocannabinoid system. The endocannabinoid system regulates and controls many sensations and other functions — pain and temperature control, learning and memory, sleep, and immune response. The cannabinoid receptors regulate and control other neurotransmitters’ levels and activity. These receptors increase or reduce the activity of any other system (pain, hunger, temperature).
The exercises increase one of the cannabinoid receptor CB1 activity. The studies show research with rodents. The circulating levels of CB1 activity increased when rodents exercised. Moreover, there is research where the endocannabinoid mechanism was researched with humans during isometric exercises.
Other mechanisms were proposed as exercise-induced hypoalgesia, such as stress and growth hormones, exercise-induced changes in the cardiovascular system via baroreceptor-related mechanisms, central pain modulatory systems, and psychological factors when we start to exercise. However, there is small to moderate proof of these mechanisms, and there is a need for broader studies.
There is a lack of studies on chronic pain and exercise-induced hypoalgesia, but it is thought that exercise-induced hypoalgesia is impaired for those people who have chronic pain. However, the first line of treatment for people with chronic low back pain is physical exercises, and the pain relief effect is small to moderate.
It's important to mention that for people with chronic fatigue syndrome, fibromyalgia, or chronic whiplash disorder, the pain intensity increases after acute exercise. The research suggests this is because people with chronic pain have more negative emotions: catastrophizing, anxiety, and poor self-efficacy. Researchers believe these feelings and negative beliefs are psychological factors that correlate with exercise-induced hypoalgesia.
Does an acute bout of exercise help with tolerating pain?
The previous paragraph shows that exercise-induced hypoalgesia starts when we are exercising or physically active. How does exercising affect pain tolerance? Different exercise routines have a good impact on the increase in the pain threshold. Therefore, it is important to do aerobic exercises and isometric and dynamic resistance exercises to reduce pain sensitivity by up to 20%.
Moreover, not only is the type of workout important but also the intensity level and duration of the exercises. The review showed that strength exercises performed at moderate to high-intensity levels have the highest effect on pain modulation. The moderate to high intensity means that people need to exceed 75% of their maximal oxygen uptake (VO2 max) and keep it for at least 10 minutes. However, acute bouts of exercise work poorly for people with chronic pain.
The endogenous opioid-related substances are in the central nervous system and locally expressed in body parts that do exercises. That is why pain sensitivity is attenuated and pain threshold increases.
To sum up, evidence of a pain-inhibitory response immediately following an acute bout of exercise is small and not for chronic disease conditions.
Regular exercise can help with tolerating pain
The longitudinal study presented how habitual physical activity can lead to an increased pain threshold in the general population. The study also showed that active people had significantly better outcomes over time when the cold-pressor test, which gradually increases pain, compared with sedentary people. The tolerance to cold (pain trigger) increases for physically active people.
Even light physical activity significantly increases the pain threshold compared with a sedentary lifestyle. Moreover, tolerance to pain increases when people start to increase their physical activity level from light to moderate or vigorous, but not vice versa.
The study shows that regular exercise helps reduce the risk of low back pain by 33% if performed two to three times a week. Furthermore, regular exercise is a safe way to reduce pain for individuals with mild to moderate chronic pain. For example, a reduction of pain sensitivity decreased in people with osteoarthritis after 8–12 weeks of exercise therapy.
During regular exercise, the body adapts to exercise loadings. Additionally, the endogenous opioid system activates more receptors responsible for the reduction of pain sensitivity.
Overall, the best way to increase tolerance to pain for people with chronic pain is regular exercise and physical activity. Acute bouts of exercise might help to increase tolerance to pain for healthy individuals as well as regular exercises.
- PloS one. Longitudinal relationships between habitual physical activity and pain tolerance in the general population.
- Journal of Pain. Exercise-Induced Hypoalgesia in Pain-Free and Chronic Pain Populations: State of the Art and Future Directions.
- European Journal of Pain. Impaired exercise-induced hypoalgesia in individuals reporting an increase in low back pain during acute exercise.
- Pain Reports. Exercise-induced hypoalgesia after acute and regular exercise: Experimental and clinical manifestations and possible mechanisms in individuals with and without pain.