When the Sweet of Warmth Becomes the Sour of Heat

May 20

With a growing pile of home projects and a few outdoor "kid-chasing" events planned for the weekend I made and almost involuntary "ooof" sound as I pulled up the weather app on my phone. Temperatures jumping from mid 70's to mid 90's in 24 hours. Ah yes, "Spring-time" in NJ. Of course this is not a complaint about the weather - I wouldn't dare. I'd much rather have heat than cold. At least, that's the story I tell myself this early on in the season, before things get really oppressive because, compared to other species, we humans are surprisingly good at functioning in the heat. In fact, some say it may be one of the greatest advantages we have allowing us to even win races on foot against horses. Whether we call it by its proper name (nonlinearity), what it looks like on paper ("U" shaped) or use terms more common to a children's book (Goldilocks phenomenon), some may be good but more is not necessarily better; we are rapidly approaching a time of year when our ability to manage body temperature can be a major difference in whether we perform at our best or struggle more than we need to. This is because cooling hard working tissues shows great promise.

For example, in a 2020 review, a research team from France outlined some of the negative impacts on performance in hot environments as well as restoration of function when certain cooling strategies were implemented.

More specifically these 3 key points are particularly important:

(1) Heat significantly impairs the ability to complete tasks lasting greater than a few minutes or in repeated efforts (e.g. multiple sets), even in elite athletes. Whether researchers measured it in power output, time to exhaustion or fitness testing (VO2Max), as the temperature went up, performance was impaired, somewhere in the range of 10-15% in most studies.

This speaks to why we advocate strongly for raising the fitness baseline before the heat really sets in. A 15% loss of a bigger-than-needed number may provide enough buffer to get by while we acclimatize, whereas 15% loss starting at a lower number may put us on the wrong side of risk.

(2) These losses are not only physical - our ability to concentrate, solve problems and perform cognitively demanding tasks also degrades as body temperature goes up. Specifically, research has demonstrated declines in working memory and errors in judgment and decision-making which of course can have major implications in higher risk or more complex environments.

(3) Cooling the system can make a significant impact. Although bigger differences were seen in "time to exhaustion" tests (up to 50% improvement in some cases), small improvements were also seen in absolute performance such as timed-events (3-9%), heavy muscular efforts (depending on the parameters and starting temperatures) and on cognitive performance.

However, it is important to note that not all cooling strategies yield the same results. Whole body cooling, such as jumping into a pool, may be the fastest but since the body is equipped with features that seem particularly well suited for heat management, it may not be necessary. For example, in the naturally hairless areas of the body such as the palms, soles of the feet and face "above the beard line", we have blood vessels that, when cooled, can lower body temperatures and increase physical performance. Other areas like the head/neck, which send information to the hypothalamus (the brain's "thermostat") can impact how cool we feel, and possibly help us to be more comfortable even in hot environments. Other areas like the chest have also been studied for the ability to quickly cool the system.

The take-away, and although especially true for individuals who do not work in temperature controlled environments, heat is an important risk and performance-limiter we face every year. Managing it better is a key strategy for staying healthy and safe as the temperatures climb. It takes some know-how, but it can be done.

For those who get our monthly webinar and educational resources, we will continue to dive into heat management as a critical preventative strategy.

Have a great weekend and stay cool, literally.

Mike E.