Lifting will not budge a healthy person's HRV

Heart rate variability and related measures of cardiac autonomic control reflect how the nervous system regulates the heart, and they have become popular markers of fitness and recovery thanks to wearables. Endurance exercise is often credited with improving these markers, but whether lifting weights does the same has been far less clear. Resistance training is now recommended widely for health, so knowing whether it changes autonomic control of the heart, in whom, and by how much, is a question with practical stakes for anyone tracking these numbers.

The authors systematically searched PubMed, PEDro and Scopus from inception to June 2018 for trials examining resistance training and cardiac autonomic control. They included randomised controlled trials, quasi-experimental trials and cross-over controlled trials in which the resistance training lasted at least 4 weeks. Autonomic control had to be assessed by linear or non-linear measures of heart rate variability, baroreflex sensitivity, or post-exercise heart rate recovery. Twenty-eight studies made it into the systematic review, and 21 of those provided data suitable for meta-analysis, covering both healthy and diseased individuals.

In healthy humans, the majority of the literature suggested no change in cardiac autonomic control following resistance training; the authors describe the effect as no or minimal. In diseased individuals the picture was different: resistance training significantly improved several heart rate variability measures, including RMSSD, the ratio of low- to high-frequency power, SD1 and sample entropy, all in directions consistent with better autonomic control. The quality assessment rated the evidence as fair overall, which tempers how firmly either conclusion can be held.

This complicates the casual assumption that any beneficial training must show up in HRV. It suggests a ceiling effect of sorts: healthy people, whose autonomic control is presumably already functioning well, have little room to improve on these measures through lifting, while people whose autonomic function is compromised by disease can recover ground. It leaves open questions about whether longer or different resistance programmes could shift healthy people's numbers, and whether combining lifting with endurance work changes the picture.

If you lift and track HRV on a watch or ring, this is a reason not to judge your programme by that number. The pooled evidence says a healthy trainee's cardiac autonomic control tends to stay put under resistance training, so a flat HRV trend alongside growing strength is entirely consistent with the research. It is also worth knowing that the benefits of lifting for the heart's regulation appear real for people with existing conditions, which reinforces resistance training's place in rehabilitation settings rather than diminishing it.