Are you sick? Is your body fighting off an infection? Well then, you’d be better off staying home, rather than going to the gym, as to allow your body an adequate convalescence. Not only that, it’s simply common courtesy due to contagion risk. Despite this highly generalized view, I thought I’d talk about at least a few of the nuances, and reasons why exercise while sick is/should be contraindicated. Exercise in general, especially during highly intense training, of which I assume most avid lifters perform, is immunosuppressive. For one, just consider the altered blood flow and general hormonal pattern, that will aim to increase exercise performance (a stressor), such as increasing substrate availability, increase chance of “survival”, etc. Essentially, your energy stores will be averted from your immune system, to your skeletal muscle. Further is the actual endocrine response to exercise/stress. This includes, notably, cortisol and norepinephrine (NE)/epinephrine (EPI). Cortisol is robustly immunosuppressive, as is quite known (through both genomic & non-genomic effects, suppresses virtually all pro-inflammatory cytokine production, inhibits telomerase in immune cells, decreases chemotaxis & immune function, etcetera). NE/EPI are also quite immunosuppressive, albeit it is a bit less known, and their effects aren’t quite as profound as that of cortisol (NE/EPI contribute to immunosuppression through less pathways - mainly directly interact with, and inhibit, NF-kB binding to DNA through inducing CREB, CRTC, and HDAC4, thus decreasing pro-inflammatory cytokine output, with a few exceptions such as IFN-gamma). Thus, these hormones are canonically immunosuppressive through different mechanisms, and even though the expression will be transient with exercise, the combination of their response, plus averted blood flow and energy stores, will certainly make a difference in immune function and hence infection clearance/severity. It’s also worth mentioning that many infections will alter, or increase production of, these hormones on their own, so you’d essentially be digging into the realm of further immunosuppression, especially as time goes on. The second aspect to consider is the vastly increased metabolic rate you’ll experience, due mainly to increased body temperature. For one, fever will be elicited due to circulating pyrogens (such as IL-1, IL-6, TNF) acting on the hypothalamus to increase prostaglandin E2 (PGE2) production. The increase in temperature will exorbitantly raise metabolic rate on its own. However, through exercise, NE/EPI will further augment the metabolic rate increase, thus increasing energy expenditure, and likelihood you would eat enough to gain muscle anyhow. Not only that, cortisol potently stimulates leptin release. Leptin will cause an increase in thermogenesis/metabolic rate through at least 4 mechanisms that immediately pop into my head: increases sympathetic nervous system (SNS) output, and thus the catecholamines NE/EPI, further augmenting that pathway; increases output of thyroid hormones, t3 sublimely increases metabolic rate of all tissues, and potentiates the body for NE/EPI; suppresses PPAR-gamma activity, increasing thermogenesis; and increases peripheral tissue AMPK expression, and inhibits that expression in the hypothalamus (central), thus subtly augmenting the previous responses. Ergo, the vast rise in metabolic rate should be lucid, and add yet another element to the contraindication of exercising while sick. Not only that, consider the greatly amplified risk of catabolism, of which exercising will only augment. The last aspect I’ll cover, is the inhibition of protein synthesis. This is more specific for times you have a viral, or intracellular bacterial infection. Key word here: intracellular, which viruses are of course. I guess the problem here is actually realizing what specific type of infection you have, and what specific organism is causing it, however, I’d rather not get into microbiology at this time, so excuse the digression. Notwithstanding that last bit, the molecular mechanism underlying this is the orthodox anti-viral state. This is facilitated through the interferons (IFNs), which activate intracellular protein kinase R (PKR), and the 2’5’-oligoadenylate synthetase. PKR phosphorylates the elongation initiation factor 2-alpha (eIF-2alpha), which inhibits ribosomal assembly and initiation, and inhibits protein synthesis. The oligoadenylate synthetase leads to the activation of RNAse L, which causes mRNA degradation, adding another element to the protein synthesis inhibition. Thus, even if you didn’t worsen your infection by causing some immunosuppression, and averting energy stores from your immune function, and overcame the massive rise in metabolic rate via food intake, you then risk it all being for nothing, as you could have diminished abilities to synthesize new proteins. Herein, I’ve outlined a few different reasons and mechanisms of why you shouldn’t exercise while you have some sort of infection. I’d also like to reiterate one point specifically - a lot of the purpose is also simply courtesy, as to not infect bouts of others. -Shane
Posted on: Thu, 26 Jun 2014 04:03:29 +0000
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