CLINICAL KNOWLEDGE MAGAZINE
4 min read
Working Out During Illness
Kacper Nowak
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Diets Premium Medical Expert • 18.03.2026
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Scientifically reviewed by a clinical dietitian:
This article has been peer-reviewed for adherence to IŻŻ, WHO, and PTGiP clinical nutritional standards.
| CLINICAL KNOWLEDGE MAGAZINE CLINICAL KNOWLEDGE MAGAZINE | min read 4 min |
| Diets Premium Medical Expert Kacper Nowak | Scientifically reviewed by a clinical dietitian 18.03.2026 |
Key Takeaways
Frequently, there is substantial uncertainty regarding undertaking a workout when our well-being has deteriorated. Generally, we have a cold in mind, as considerably graver states of health usually exclude any form of physical exertion right away.
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Basic facts regarding exercise physiology
During the execution of exertion, particularly of a strength nature, minor injuries arise in the working muscles. These micro-damages manifest as muscle soreness that we experience the next day after exercise (so-called DOMS), commonly referred to as acids. The inflammatory state that arises then inside the muscle cells is a signal for the body to initiate a series of responses. These are regulated, among other things, by our immune systems until the tissue that was exposed to stress is regenerated by acid and reinforced by supercompensation processes. Furthermore, it is important to take into account that stress associated with physical exertion, especially long-lasting, increases the level of cortisol in the blood, which is responsible for the energy supply in the form of glucose by increasing its concentration in the blood. This is achieved through gluconeogenesis and the breakdown of fatty acids into ketone bodies.
Cortisol - a hormone with immunosuppressive action having a thickness not exceeding 10 mm
Cortisol belongs to the group of glycocorticoids, hormones that exhibit anti-inflammatory and immunosuppressive activity. This means that during exercise during illness, our immune system redirects its activities to focus on post-training recovery. Furthermore, cortisol's immunosuppressive effect prevents the production of antibodies and immune cells from being disrupted in order to restore muscle cells to their previous state. Depending on the stage or severity of the infection, our health status after training may deteriorate or remain unchanged. It is very rare to achieve health improvement, especially if the effort took place outdoors or if large loads engaging the largest muscle groups were used during its duration. This can be compared to taking an antibiotic, which usually requires long-term treatment, despite the fact that the well-being is already significantly better. Within the body, there are still remnants of infection that may multiply again and attack.
Tailoring exertion to sensation
If we've already decided that we're going to exercise despite our illness, then there are a few recommendations to follow. Endurance training on fresh air, sprints, peripheral training or HIIT don't seem to be a good idea. Strength training seems to meet the criteria, provided we choose a range of repetitions that cause less microdamage in the muscle cells. The literature recommends avoiding the range of 6-12. However, this is helpful information, because we can reduce the damage to the muscles that we have in the range, and we can only consume our health-related body feelings as much as we already have after 15 days of stretching. And if we try to do this, we should do it more than 30 percent, and then we can't even do it through a week of training. The best option is not to perform a series to muscle failure, but to perform a so-called relief week, where we reduce the weights by about 30% and perform exactly the same range of repetitions as we had in the plan, and focus on the technique of the executed exercises. In the case of a cold, there are no contraindications for training, but an infection that affects further areas of the respiratory system and has symptoms such as persistent cough and fever is a clear signal to stay at home.
Kacper Nowak
Diets Premium Medical Expert
Member of the Diets Premium clinical editorial board. Specializes in medical diet therapy, metabolic health, and nutritional planning.
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