Optimize Resting Heart Rate and HRV
Siim Land explains that a low resting heart rate paired with high HRV is the optimal combo, contrasting with the aging phenotype where both drop. He sets a target of under 50 bpm, ideally 35-45 bpm. To improve these metrics, he emphasizes that cardiorespiratory fitness is key: HIIT and zone 2 cardio are particularly effective for HRV, while resistance training alone doesn't consistently raise HRV. An underrated factor is walking; a Fitbit study showed a linear correlation between step count and HRV, up to 20,000 steps/day, via improved blood flow, lymphatic drainage, and nervous system regulation. He has practiced intermittent fasting for over 12 years and finds that 12-16 hour fasts lower his resting heart rate and raise HRV, but warns that longer 48-hour fasts can induce autonomic stress and lower HRV. Another lever is meal timing: food in the stomach at bedtime keeps heart rate elevated and HRV reduced, so he stops eating 4-5 hours before bed. Sauna and cold exposure provide hormetic stress that mimics exercise's supercompensation effect. He also notes that lower body fat percentage correlates with lower resting heart rate, likely due to reduced metabolic rate, and recommends a Mediterranean diet for its research-backed HRV benefits, but insists that the most important factor is simply not being overweight.
HIIT and zone 2 cardio improve stroke volume, vagal tone, and heart rate recovery, lowering resting heart rate, while HIIT specifically boosts HRV through autonomic flexibility. Walking enhances lymphatic drainage, lowers stress hormones, and directly increases HRV (Fitbit study showed linear increase up to 20k steps). Intermittent fasting (12-16h) triggers metabolic switching and parasympathetic activation, reducing resting heart rate in the fasted state. Early time-restricted eating prevents postprandial thermogenesis from raising heart rate during sleep. Sauna and cold exposure act as exercise mimetics: acute heart rate elevation followed by supercompensation leading to lower resting rate. Leanness reduces metabolic demand and sympathetic drive.
I personally have been doing intermittent fasting for you know 10 years longer than 12 years by now so uh it does lower resting heart rate especially in like the fastest state and uh increases HRV in this kind of a 12 to 16 hour window. I wait at least 5 hours, four or five hours before bed with the food.
the best resting heart rate so lower resting heart rate which I think optimally should be less than 50. So uh something between 35 and 45 is kind of the sweet spot.

