High Intensity Health · Dr. James DiNicolantonio · 29 min
Key Takeaways: Salt, Sauna & Exercise
Dr. James DiNicolantonio — cardiovascular research scientist and bestselling author of The Salt Fix and WIN — makes the case for three underutilised performance levers: salt preloading, sauna heat adaptation, and resistance training. The science is established. The application is rarely discussed in mainstream fitness contexts.
20+
additional minutes of vigorous exercise from salt preloading (vs 1–2 min from beta-alanine)
8–10%
blood volume drop in the first 5 minutes of vigorous exercise — preloading prevents this
2 weeks
daily sauna sessions needed to produce measurable heat adaptation
Core Insights
Blood volume is the linchpin of exercise performance. The single biggest adaptation produced by consistent endurance training is expanded blood volume. Elite athletes carry 40% more blood than sedentary adults. Salt preloading mimics this effect acutely — boosting cardiac output, improving heat dissipation, and enhancing oxygen and nutrient delivery to working muscle.
Salt is 10–20x more effective as an ergogenic than most supplements. Beta-alanine — one of the more evidence-backed performance supplements — extends vigorous exercise capacity by approximately 1–2 minutes. Optimal salt preloading extends it by 20+ minutes. The mechanism is blood volume expansion, which prevents the performance-limiting drop that occurs within minutes of intense exercise.
The optimal preload protocol is precise. For competition or high-intensity sessions: 3,000–4,300mg of sodium with 26–34oz (roughly 800ml–1 litre) of fluid. For typical training: 1,000mg sodium + 10–16oz water. Slightly hypertonic solutions (a little more salt than blood concentration) outperform isotonic matches.
Not every session should use maximal preloading. Allowing mild dehydration to develop during regular training drives its own blood volume adaptation over time. Reserve heavy preloading for competitions and genuinely hard sessions — this preserves the adaptive stimulus of hydration stress while providing maximal support when performance matters most.
Sauna produces heat adaptations that transfer to exercise performance. Two weeks of daily sauna use lowers baseline core body temperature — expanding the thermal buffer before heat-sensitive enzymes begin impairing ATP production. Sweat also becomes more dilute, meaning less electrolyte loss per session. Both adaptations directly improve training capacity and endurance.
Heat adaptation mirrors endurance adaptation. The physiological changes from regular sauna use — increased plasma volume, improved cardiovascular efficiency, better thermoregulation — are broadly similar to those from aerobic training. For people who cannot add training volume, regular sauna sessions provide some of the same substrate.
Resistance training 3–4x/week is the minimum for sarcopenia prevention. Muscle mass is the primary defence against age-related frailty. The body preserves what is consistently used and economises ruthlessly on what is not. Thirty to sixty minutes of resistance work, three to four times per week, provides the signal needed to maintain muscle mass across decades.
Functional movement can substitute for conventional gym work. Shadow boxing, martial arts, resistance bands, bodyweight movements — anything that loads muscle through a meaningful range of motion counts. The form matters less than the consistency and load.
Practical Protocol
For daily training: 1,000mg sodium + 10–16oz water 30–60 minutes before exercise. This provides blood volume support without fully blunting the adaptation signal from mild hydration stress.
For competition or hard sessions: 3,000–4,300mg sodium + 26–34oz fluid. Allow 60–90 minutes for absorption and volume expansion before the session begins.
For sauna: Daily sessions for at least two weeks to produce meaningful heat adaptation. 15–20 minutes at moderate temperature is sufficient. Ensure adequate hydration and salt replacement after each session — the electrolytes lost in sauna sweat are the same ones that support performance.
Resistance training: 30–60 minutes, three to four sessions per week, consistent across years. Begin with compound movements, build progressive load over time, and treat it as non-negotiable infrastructure rather than optional exercise.
Worth Remembering
"The biggest adaptation the body makes to endurance training is increasing baseline blood volume. Salt preloading gives you that acutely — before the session even starts."
— Dr. James DiNicolantonio