Most people think of strength training as a muscle thing. Bigger biceps, stronger legs, better posture. But a growing body of research shows that resistance training also reshapes your autonomic nervous system — the part that controls your heart rate variability.
And the effect sizes are not small.
The Numbers
A 2025 study of physically active young adults compared people who primarily did resistance training to those who did cardio. The resistance training group had RMSSD values of 75.3 ms versus 37.5 ms in the cardio group. That is twice the parasympathetic activity, with large effect sizes (Cohen's d = 1.15 to 1.55).
Interestingly, frequency-domain measures (HF power, LF/HF ratio) did not differ significantly between groups. This suggests that resistance training improves HRV through different pathways than aerobic exercise.
A 2024 meta-analysis of 16 randomized controlled trials with 623 participants confirmed the pattern. Both aerobic and resistance training improve time-domain HRV (RMSSD and SDNN). Exercise type did not significantly modify the outcomes. Both work.
Different Roads, Same Destination
Aerobic training improves HRV primarily through enhanced cardiac vagal modulation — your heart gets better at responding to the vagus nerve. The mechanism is central.
Resistance training appears to work differently:
Improved arterial compliance and blood pressure
Enhanced baroreflex sensitivity
Better body composition and metabolic health
Reduced chronic inflammation
The pathways are peripheral and metabolic rather than central. Your nervous system benefits, but through the body rather than through the heart directly.
This matters practically. If you hate running but enjoy lifting weights, the evidence says you are still building autonomic resilience. You do not need to force yourself onto a treadmill to improve your HRV.
What the Research Recommends
Based on the available evidence, the minimum effective dose looks like this:
2 to 3 sessions per week
At least 8 weeks for meaningful adaptation
Higher intensities are more effective than low
Compound movements (squat, deadlift, press, row) over isolation exercises
This aligns with a 2021 systematic review that concluded all types of exercise intervention showed HRV improvement, but higher training intensities and frequencies were more likely to produce results.
The Timing Catch
One important caveat: immediately after a resistance training session, your HRV will be suppressed. This is normal. Your body is in recovery mode. Sympathetic activation is high, parasympathetic is low.
The improvement happens over weeks and months of consistent training. If you measure your HRV the morning after a heavy squat session and see a low number, that is acute suppression, not a sign that lifting is bad for your nervous system.
This is also why overtraining wrecks HRV. The chronic adaptations are positive, but they require adequate recovery between sessions. More is not always more.
Resistance vs Aerobic: Head to Head
Here is how they compare based on the current evidence:
RMSSD: Both improve it.
SDNN: Both improve it.
HF power: Aerobic training increases it; resistance training may not change it.
LF/HF ratio: Aerobic decreases it; resistance training shows variable results.
Effect size: Resistance training shows large effects (d = 1.15 to 1.55); aerobic shows moderate to large.
The 2024 meta-analysis is the key finding here: exercise type did not significantly modify RMSSD or SDNN outcomes. For the metrics that matter most in day-to-day HRV tracking, resistance training performs as well as cardio.
The Bottom Line
Lift heavy things regularly. Your muscles will get stronger, obviously. But your autonomic nervous system is adapting too — building the kind of parasympathetic resilience that shows up as higher HRV scores over time.
The best exercise for HRV is the one you will actually do. If that means barbells instead of running shoes, the evidence says you are on solid ground.
Sources
2025 Young Adults Study — Resistance training and HRV in physically active adults (PMC12061358)
2024 Meta-Analysis — 16 RCTs, 623 participants on exercise and HRV (PMC11250637)
2025 Long-Term Exercise Meta-Analysis — HIIT, aerobic, resistance, mind-body (Frontiers in Physiology)
2021 Systematic Review — All exercise types and HRV improvement (Frontiers)