Exercise has many effects on your body, most of which are good, and is why we humans do it to stay healthy. However, some of those changes, especially under very intense regimens, can have unseen consequences that might be bad. Your immune system, for example, responds to different types of exercise (aerobic endurance versus anaerobic resistance) by altering which branch of your immune system is dominant at that time. Both kinds of exercise tend to increase the more specific ‘humoral immunity’ (B-cell immunity below) over the more general ‘cell-mediated immunity (T-cell immunity below), though the routes to get there are very different for the two kinds of exercise. However, most of what we know about exercise-immunity tradeoffs is from humans and rodents. What about in other animals that have limited access to resources? Might simple energy limitation cause overall immunity suppression when energy is diverted to athletic performance?
My former student Andrew Wang and I studied this experimentally with green anoles. We trained lizards for endurance on a treadmill, or for resistance with weights on a racetrack, for 9 weeks, and compared those to a sedentary control group. Both of these types of locomotion are important to anoles in the wild, and the training schedule was meant to simulate the high end of movement patterns in nature. We then subjected them to three immune challenges: (1) swelling response to phytohemagglutinin (cell-mediated immunity), (2) antibody response to sheep red blood cells (humoral immunity), and (3) wound healing ability (integrated response across all parts). We expected that if simple energy limitation explained tradeoffs, all immune measures would decrease, with endurance-trained suffering the most. If protein limitation was the reason for tradeoffs, then we expected all immune measures to decrease, with sprint-trained suffering the worst. Finally, if the response is due to changes in molecular pathways specific to type of exercise, we expected humoral immunity to be favored over cell-mediated in both trained groups.
Figure 1 from Wang and Husak (2020)
Our results did not support only one of our hypotheses. Endurance-trained lizards had the lowest cell-mediated immunity, whereas sprint-trained had the lowest wound healing ability. Antibody production did not differ among treatments. Our hypothesis of sprint-trained lizards (or even endurance-trained) having the lowest overall immune function was not supported, suggesting that energy limitation alone does not explain immune system alteration. For sprint-trained lizards, energy was likely important, since wound healing, an expensive task, went down the most in that group. For endurance-trained lizards, though, the change in T helper cell production favored humoral over cell-mediated immunity. Since both types of exercise favor humoral immunity, it was not too surprising that antibody production did not differ among treatments. Lots of questions remain to be answered, though!
What does this all mean? In nature, individuals vary dramatically in how much, and for how long, they move around their environment. Those that are more active, thus likely have different immune capabilities compared to more sedentary individuals. It would be very interesting to see how natural variation in survival strategies, high-performance versus high-immunity, affected success in nature. This is a wide-open field for anoles and other reptiles!
Source: Wang, A. Z. and J. F. Husak. 2020. Endurance and sprint training affect immune function differently in green anole lizards (Anolis carolinensis). Journal of Experimental Biology
- Exercise and the Immune System in Green Anoles - January 6, 2021
- Exercise Can Kill You (If You’re an Anole)! - May 10, 2019
- Leptin Mediates Tradeoffs in Green Anoles - February 2, 2019
Rick Wallach
Are there really enough similarities between the human and reptilian immune systems to be drawing such anthropomorphic conclusions? I’m not comfortable with the way this was written, I’m afraid. I hope the experiments themselves drew a sharper distinction than this article does.
Jerry Husak
There is amazing similarity between the immune systems of vertebrates, as far as we know. Not everything is completely identical (also true for rodents, which are the typical models), but we know the most about humans for obvious reasons, so that is where hypotheses start. There are no anthropomorphic conclusions here – no extrapolation to humans. What specifically is it that makes you so uncomfortable?
Rick Wallach
Jerry (if I may): I think most of all it was the repeated use of the possessive pronoun “your” in second person in that first paragraph, setting up a more extenuated analogy between human metabolic process and those of our beloved anoles. As a (retired) English professor who taught science and business writing as well as literature, I’m wary of the inadvertent equivocation of analogy with identity. I understand that this was an article, not strictly speaking a “paper,” and I meant no challenge to the data, only the verbal construction.
Jerry Husak
Fair point, Rick. You’ll notice, however, as I’m sure you did when you graded papers, that “your” was only used in the beginning when explicitly talking about the human (your) immune system to set up the topic. It was not used in the context of the experiment or results. I understand that many like to be critical for criticism’s sake, but the pedantry was unwarranted here. There was no equivocation of analogy with identity. It was a set up to reptile immune systems. Perhaps we can agree to disagree.
Rick Wallach
You asked me what made me uncomfortable and I told you. Pardon my “pedantry” – an unwarranted and unnecessary term, frankly, especially considering you said my point was “fair” and also considering my initial post asked for clarification. That hardly constitutes pedantry.
And no, I’m not interested in being critical for the sake of being critical. As a matter of fact after several years on this blog I think this was the very first time I ever wrote something didn’t feel right to me.
But when you use an apostrophic address like that “only” at the beginning or introduction to an article, you are framing your rhetoric (in the technical, not pejorative) sense and establishing expectations it would be extended to and legitimate for the entire piece.
Douglas Menke
“Your” is clearly referring to humans. At the end of the first paragraph Jerry then asks whether immune responses in other animals are similar to those found in humans. I did not find the construction of this piece to be confusing or ambiguous.
Jerry Husak
Life’s too short for internet arguments. I’ll read some of your published works for tips, Rick. Thanks for your interest in anoles, and I hope you have a great weekend.