By Alex Maycock MSc, BPHE, NCCP T2T Coach
Have you ever noticed marathon runners switching wet hats during a race or putting wet towels or ice sleeves around their necks? Our bodies love to maintain thermal homeostasis of 37ºC, and the purpose of athletes partaking in these practices is to decrease the rate at which the individual becomes hyperthermic (the rise in core temperature above homeostasis)! With a brutal heat wave across Canada in May - and surely a hot summer ahead - it is only intuitive to consider best practices for mitigating heat exhaustion.
Pre-cooling techniques, like ingesting an ice slurry or sporting an ice vest, have their place in performance settings to attenuate hyperthermia. However, although these practices have mixed support in the literature to reduce or delay heat exhaustion, they could be perceived as uncomfortable, cumbersome, or time intensive. If you don’t have a team of support staff to prepare these tools for summer heat, other important considerations should be first taken or done in addition to pre-cooling! These summer training strategies include: 1) Maintaining euhydration, 2) exercising in shady locations, and 3) exercising at dawn and dusk.
Some signs to be cautious of when exercising in the heat include the absence of sweating, headaches during or after training, and an increase in heart rate at the same workload. All of these signs are related to hydration status.
Hypohydration (dehydration) symptoms
An increase in heart rate while exercising at a steady state, for example, six minutes per kilometre pace, is an indication of hypohydration. When exercising in the heat, our blood moves towards our skin to dissipate heat through sweating. This is fantastic as evaporative heat loss allows us to cool, but it does decrease the amount of water in our bodies. Further, water is stored within the blood as plasma. Without ingesting adequate liquids, our blood volume can decrease during exercise. And with less blood volume, stroke volume will decrease. To compensate for a reduced stroke volume, the heart rate must increase so that the desired workload is maintained. This is because cardiac output, the amount of litres one’s heart pumps per minute, is the function of heart rate (beats per minute) and stroke volume (the amount of blood per beat).
Figure created via Biorender.com.
Cardiovascular drift figure: Cardiac Output, the amount of litres one’s heart pumps per minute, is the function of heart rate (beats per minute) and stroke volume (the amount of blood per beat).
Ultimately, an increase in heart rate at a set workload is termed cardiovascular drift and is a classic example of an athlete needing to ingest more water. This is highly individual, and pre and post-exercise nude weighing could be a good option to ensure you are, in fact, ingesting adequate fluid by maintaining body weight.
So, this summer, before downing some ice chunks or wearing some cumbersome vest full of ice, bring along a portable water carrier for training sessions. Skiwax.ca has a selection of drink carriers here.
The First Lap Coaching Services:
Offers year-round coaching for cross-country skiers. We offer individual and group coaching programs through monthly programs, clinics and lessons. See our Programs and Fees page: https://www.thefirstlap.com/blank-4
About the author:
Alex Maycock, MSc, BPHE, NCCP coach, has a masters degree specializing in exercise and environment physiology and ergogenic aids. He coaches the varsity Nordic ski team at Nipissing University and has a passion for athlete development. Alex competed as an elite varsity Nordic ski career representing Canada at the 2019 and 2023 FISU World University Games. Coaching and exercise physiology are natural progressions following his athletic and academic background. You can train with Alex by reaching out on his website https://maycockperformancecoach.com/
Forest Fire Smoke Map North America: https://firesmoke.ca/forecasts/current/