The word inflammation no doubt conjures up images of a swollen hand from a bee sting, or a swollen ankle from a sprain. Few people, however, consider how ubiquitous the inflammatory response is in the body, like your last sunburn, or how it impacts either health or performance. In this short article series, I will explain what inflammation is and how it influences disease and your training.
All inflammation is driven by the immune system, but how the inflammation is modulated depends on numerous immune and tissue chemicals, globally called cytokines. The actual site of release can influence their actual impact on health; e.g., immune cells release cytokines (good or bad), muscles release myokines (typically bad), fat/adipose release adipokines (generally bad). Also, different cytokines can be PRO-inflammatory, like tumor necrosis factor (TNF), or ANTI-inflammatory, like interleukin (IL) – 10. Other chemicals and hormones, like cortisol, are also anti-inflammatory, and play an important role in health and training adaptation. In general terms, obesity is considered inflammatory and the excess adipose tissue has been shown to release pro- inflammatory chemicals, while exercise, on balance, has been shown to be anti-inflammatory (Febbraio 2002; Pedersen 2011, 2006). It’s not surprising why exercise improves atherosclerosis or diabetes, both inflammatory related diseases, even without weight loss (ie, reduction in obesity).
The last point is often confounding to many, particularly when health professionals have for years espoused the absolute need for weight loss. While it is true, that losing 10, 20 or 50 lbs for overweight individuals can have a profound impact on metabolic and cardiovascular related diseases, weight loss need not be the end goal. In fact, several lines of research continue to show that people can be “fit and fat”. This is especially important for individuals who have tried and failed to lose significant weight; YES, you can be healthier if you continue to follow a “good” diet and exercise. Again, the reason why lies in the exercise itself. Here’s how it works.
Interleukin (IL) – 6 is considered a complex master controller of inflammatory responses in the body, and is known to have both pro and anti-inflammatory roles; it is also believed to be intimately involved in fuel mobilization in the body. For this article, we’re going to stick with just exercise and IL-6 as a myokine (vs the cytokine released by immune cells). If it seems complicated, it is! Again, IL-6 is largely anti-inflammatory when released during and after exercise. The longer, and to a lesser extent the harder, you go, the more IL-6 is squeezed out of the muscles (Figure 1). This appears to be a key reason for why exercise has profound and ubiquitous effects throughout the body.
As illustrated in figure 1, exercise improves glucose uptake through a number of mechanisms. For diabetics, particularly those who are insulin resistant, IL-6 increases lipolysis (fat release) and increases glucose uptake both directly and indirectly. Specifically, cell transporters responsible for uploading glucose (GLUT-4) are positively stimulated by IL-6 and other mechanisms. Indirectly, however, IL-6 activates IL-10, which has been shown to inhibit TNF. TNF is known to inhibit GLUT-4, so knocking that out, allows for greater GLUT-4 mobilization. In layman terms, IL-6 not only adds more trucks to your shipping company, it also repairs the roads and removes road blocks that slows or prevents your deliveries. It may also make your trucks more efficient; ie, improves insulin’s action on the cell.
My hope is that this brief introduction to inflammation has stimulated your interest and understanding of inflammation. The inflammatory response in the body is complex and far-reaching, but it can be used to work for us through the use of exercise. In the concluding article, I will discuss why inflammation is important to training, as well as why trying to artificially reduce it, by using NSAIDs for instance, may not be in our best interest.
A nice video on the inflammatory response