One of the easiest to monitor health trends is resting heart rate. Most popular fitness trackers will just pull this in every day. Some, like Whoop, use it to help determine if you are having an off day. Many people have said that resting heart rate along has been a leading indicator of sickness, especially since it is otherwise a stable metric. Apple Watch resting heart rate shows up in the health app of Apple products.
There’s not much you can do to alter resting heart rate day to day. Getting sleep and staying physical fit will generally keep it lower. losing weight helps for the most part as well. But if you want to see a day to day shift in resting heart rate, a sure fire way is to go to a significantly higher altitude. For example, fly or drive (or hike) from sea level up to 7000ft and it’s almost guaranteed to show up in a resting heart rate menasurment.
The two outlier days over a month were at 7000 ft above sea level, all other days were at 500 ft above sea level. This is not conclusive as it is only a sample from one person, but it would seem that average resting heart rate is affected by sea level. Of course this makes sense since it’s no secret that high altitudes make it harder to breath due to the lower air pressure.
It’s not hard to find out what altitude you are at, so long as you have a smartphone around. There are a number of apps or searches that make that information easy to get. How much a specific altitude will effect heart rate depends on a number of other factors.
The spikes in heart rate on altitude days was about 20%-30%, although that’s on a baseline of around 50BPM. All of these readings were automated from an Apple Watch reading. There isn’t much to do short term to change resting heart rate, but sleeping on a mountain will change it.
Maybe not surprisingly, VO2 max also went up on a run at altitude. It was not an outlier though, and even continued to trend up in the days following back at sea level. VO2 max is easy to anectodally tie to major training blocks or down periods, if tracked over a longer time frame.
In this chart the decline at the beginning of the year was come down from a 6 week training block that resulted in a 5k personal record.
Seeing this impact is a good reminder to take it easy the first few days at altitude. Doing other things right, like getting good rest and staying hydrated, may help ease the effects of altitude. Generally speaking it is hard to tell if your resting heart rate is higher, but it’ll be evident during short activities like climbing stairs or lugging suitcases around a hotel. You also can’t do much to bring the resting heart rate down when it is caused by altitude exposure. It is primarily an indicator of environment, even if it can be slightly swayed by meditation or good rest.
Apple Watch Resting Heart Rate for the Year
The trend in a year for a resting heart rate is not very insightful. Unless there was a major sickness or significant change in fitness, this reading will be fairly flat. Even the impact of altitude for a few days will be flattened out in a trend line as things return to normal.
Resting heart rate is useful to keep an eye on, in order to avoid over exertion. Otherwise the metric is insufficient by itself to provide a training or goal metric to focus on.