Recovery of the Immune System After Exercise
Written by Ben Bunting: BA(Hons), PGCert. Sport & Exercise Nutrition. British Army Physical Training Instructor.
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Recovery of the immune system after exercise is very important, as it allows your body to repair the damage caused by a hard workout.
There are several factors that impact this process, including diet, carbohydrate intake, and timing of food intake.
This article discusses how they relate to one another, and explains how to maximize your recovery.
IL-6 and TNF-a
Tumor necrosis factor-a (TNF-a) is a pro-inflammatory cytokine released into the blood by circulating monocytes and lymphocytes.
It may play a role in tissue degradation by invading macrophages. In addition, it is known to induce apoptosis of myocytes.
The aim of this 2015 study was to examine the relationship between gene expression of TNF-a and recovery of the immune system after heavy resistance exercise.
Gene expression of TNFR1 was measured on CD14+ monocytes by flow cytometry and a reverse transcriptase-polymerase chain reaction (RT-PCR) was performed in peripheral blood mononuclear cells (PBMCs) to determine the extent of the cytokine response to exercise.
The peak plasma TNF-a concentration was significantly higher in the resistance trained group than in the control group.
The increase was 17-fold. However, this was not found in males or obese subjects.
This result is not surprising given that resistance training is believed to affect the body's immune system in a variety of ways.
Plasma IL-6 concentration was also increased after exercise. The concentration peaked at 4.8 pg/ml at the end of the exercise and decreased after 24 h. However, it was still elevated at 2 h into recovery.
These results suggest that the IL-6 concentration is probably attributable to the elevation of circulating lymphocytes and monocytes.
Circulating leukocyte counts were elevated during exercise, and remained elevated for the first 24 h after the IP. After 48 h, these numbers returned to normal. Interestingly, the mRNA copy number per microgram of total RNA for IL-6 was not affected by exercise.
Plasma cytokine concentrations were measured in six exercising subjects. TNF-a and IL-1b were elevated during IP.
Despite the increase in the plasma cytokines, the mRNA copy number for IL-1b was not changed in exercising subjects.
Lymphocyte concentrations
If we can understand the effects of exercise on the immune system, we will be able to guide athletes in their choices of sports and help prevent infectious diseases. This knowledge can also be used in clinical medicine.
Exercise induces changes in the immune system that can affect resistance to infection, malignancy, and immunosuppression.
These changes are mediated by a number of factors, including neuroendocrine and metabolic factors.
In particular, acute exercise increases blood cytokines. However, these cytokines do not always reflect increased production of intracellular cytokines. Instead, they may be a result of muscle damage.
Exercise has been found to increase the number of lymphocytes, particularly neutrophils.
The lymphocytes are then mobilized into the blood circulation. Increased concentrations of these cells are associated with an inflammatory response. They may also lead to suppression of lymphocyte proliferation.
Several studies have shown that acute exercise alters the lymphocyte proliferative capacity.
Specifically, the production of interferon g by PBMCs is reduced. However, this response is not seen at resting values. Similarly, the production of IL-2 by PBMCs is insignificant at resting levels.
Acute exercise has also been linked to changes in lymphocyte subsets. The T-helper (CD4) and T-suppressor (CD8) subsets were increased immediately after exercise. NK and Th1 cell subsets were decreased. Moreover, the CD4:CD8 ratio was increased.
Exercise-induced changes in the immune system can have significant clinical consequences. For example, the increased circulating concentration of cytokines and the concomitant inflammatory response may lead to an increased risk of infections.
However, the effects of exercise on the immune system have not been fully investigated. Some studies have been performed on adults and children. There is a paucity of information on the effect of exercise on children.
Interactions with carbohydrate intake
Exercise induces changes in the immune system. These changes have clinical implications.
For example, strenuous exercise is associated with a decrease in host protection from upper respiratory tract infections (URTI) in the days following exercise.
Depending on the measures of immunity, this effect may last a day or more.
The underlying mechanisms of exercise induced immunosuppression are unknown. However, it is known that the function of NK and T cells is inhibited after intense long duration exercise.
IL-6 and TNF-a concentrations are increased. These cytokines are also increased by chemokines IL-8 and MIP-1b.
In contrast, n-3 PUFA have been found to attenuate inflammatory responses and reduce the incidence of infection. This may be due to their ability to counteract latent immunosuppression.
Carbohydrate intake has been found to moderate the magnitude of the cytokine response to exercise.
Various carbohydrate countermeasures have been shown to reduce stress hormones, attenuate inflammation, and improve recovery from metabolic perturbations.
It has been hypothesized that carbohydrate ingestion is linked to a reduction in muscle damage, which may contribute to reduced post-exercise inflammation.
This is due to the fact that carbohydrates inhibit adipose tissue lipases, increase plasma insulin, and reduce the breakdown of triacylglycerol and free fatty acids.
Several studies have demonstrated that a high concentration of circulating cytokines is indicative of inflammation.
Some studies have suggested that these concentrations increase with strenuous exercise. Athletes, in particular, experience increased inflammation during heavy training.
Despite these findings, however, the extent to which carbohydrate intake has an influence on the immune response to exercise has yet to be fully explored.
Considering the limited number of studies, it is difficult to determine whether carbohydrate intake has a direct impact on the immune response to exercise. More research is necessary before this question can be answered.
Post-exercise immune function depression
If you're an athlete, you may be concerned about the recovery of the immune system after exercise.
A weak immune system may result in fatigue, infections and other nagging symptoms. While the immune system is resilient and can fight back, intense, prolonged exercise can impair its functions.
Exercise can also increase your risk of developing a cold. It is estimated that the average adult has about two to three colds per year.
However, some research shows that strenuous exercise can actually suppress your immune function.
Specifically, the lymphocyte count decreases below baseline, and a number of inflammatory cytokines are produced.
In addition, some studies have shown that the production of IL-6, an interleukin, increases after exercise.
Another cytokine, MIP-1b, is increased by strenuous exercise. This inflammatory protein is produced by macrophages. These cytokines also increase soluble TNF-a receptors.
Exercise immunology
Exercise immunology is a branch of immunology that is interested in the effects of physical activity on the immune system.
It is a field that encompasses many scientific disciplines and is not limited to exercise physiologists. Several scientists have conducted research on this topic.
Researchers have also looked at how stress and psychological factors affect your immune response.
Chronic stress can lead to cardiovascular disease, diabetes, and cancer. Stress releases cortisol, epinephrine, and norepinephrine.
These hormones influence the HPA axis, the autonomic nervous system, and other pathways that control immune function.
Moreover, high levels of stress can lead to chronic inflammation. Although the effect of chronic stress is well-known, the specific ways in which these stressors affect the body and how they influence immune function is less well-understood.
Studies have shown that carbohydrate consumption during exercise is associated with limiting the effect of exercise-induced immune depression. Athletes should consume approximately 30 to 60 grams of carbohydrates per hour while exercising.
Diet and timing of food intake
The question of what to eat after exercise is not as simple as it might seem. However, the right diet and timing of food intake can play a key role in restoring your immune system to its fullest potential.
For most people, the ideal timing for a wholesome meal is a bit less than two hours before activity.
There are numerous micronutrients that contribute to the health and function of the body. For example, a good diet should contain sufficient amounts of vitamin C and iron to promote a robust immune response.
A healthy fat intake may also provide benefits, particularly in terms of improving overall fitness.
An adequate amount of vitamin D is also required to help your body respond to disease-causing agents.
Keeping a balanced diet is the best way to ensure that you get all of the vitamins and minerals you need.
Taking a multivitamin and zinc supplement on a daily basis is another way to keep your immune system in tip-top condition.
It is also worth mentioning that the ideal timing for a snack after exercise is about 30 minutes.
Alternatively, you might opt for a post-workout recovery beverage. This is the best way to ensure that you are maximizing the benefit of your workout.
As with any endeavor, the right approach can minimize the risk of getting an infection.
One effective way of achieving this goal is by following the most practical tips and tricks.
Some of the more practical suggestions include avoiding stress, eating a well-balanced diet, exercising regularly, reducing your exposure to toxins and getting enough sleep.
Another way to optimize the health benefits of exercise is by ingesting the right amount of carbohydrates, fats and protein.
Recovery of the Immune System After Exercise Conclusion
The body's immune system is central to the body's defense against infections. It is characterized by two branches, the innate and adaptive.
In response to infection, the innate arm of the immune system sends out warning signals to the adaptive branch of the immune system, letting it know that it should start fighting off the infection.
Exercise produces a strong anti-inflammatory response and promotes the release of anti-inflammatory cytokines such as IL-6.
It also increases the concentration of the proinflammatory IL-8 and the soluble tumor necrosis factor-a receptor (TNF-a).
However, these effects are not always accompanied by a increase in the excretion of immune cells.
Exercise-induced changes in the immune system can have clinical consequences.
For example, prolonged exercise is associated with reduced resistance to upper respiratory tract infections. A number of researchers have studied this relationship.
During exercise, the heart rate increases, due to adrenaline. This raises the body's oxygen demand, and the body's circulatory system calls on the white blood cells to do their job.
These cells are then deployed to other bodily locations, where they are expected to look for an infection.
After an intense bout of exercise, the distribution of the immune cells changes. A portion of the immune cells are released into the blood, while others are deposited in other locations.
As a result, the amount of these cells in the blood decreases.
These findings suggest that the body's immune system is not fully recovered from an intense bout of exercise. Instead, it may be in a state of temporary depression. Typically, this transient suppression of the immune functions lasts for 24 hours.
