Exposure to hot temperatures optimizes blood flow to heart and skeletal muscles because it increases plasma volume. This can lead to enhancements during your next workout or competition when your core body temperature becomes elevated AGAIN.
Another (beneficial) side effect seen from this is a reduced heart rate during the same workload. In other words, after heat acclimation you can complete the exact same endurance work but with a lower heart rate! That’s a better athlete.
One study found an impressive increase in performance after just two 30 minute sauna sessions for three weeks POST workout. The participants experienced a 32% increase in running time until exhaustion compared to baseline (non heat acclimation).
They also found a 7.1% increase in plasma volume and 3.5% increase in red blood cell (RBC) count – more red blood cells increase oxygen delivery to muscles. It is thought that heat acclimation boosts the RBC count through erythropoietin (EPO) because the body is trying to compensate for the corresponding rise in plasma volume. Btw, EPO is one performance enhancing drug that has been abused by endurance athletes, like some in the tour de France. But this is the natural stuff!
Another study found a 4.9% improvement in a 5km run in hot conditions (33 C). [Zurawlew et al., 2016]
How Do I Apply This?
Whether or not heat acclimation benefits transfer to boost in endurance activities NOT in hot environments remains to be determined, although, it is currently being investigated. [Minson and Cotter, 2016]
However, the potential benefits if exercising in a HOT environment seem promising. Based on these studies, try the following:
Three weeks before a major competition outdoors:
- use the sauna for 30 minutes two times per week
- do this immediately following (conditioning) training sessions.
- be sure to drink adequate amounts of filtered water to replenish lost liquids and prevent dehydration
Unfortunately, most of these studies use small sample sizes and MEN only. However, there is another interesting benefit of heat conditioning that may hold particular importance for female athletes…to be addressed in future posts.
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