The other day I was riding my bike through the park and I noticed there were a lot of runners running with poor form. The easiest thing to notice when passing by quickly on the bike is how people hold and swing their arms. It appeared to me that they were working unnecessarily hard. I began to wonder how something as simple as arm swing could affect someone’s pace, run cadence, and heart rate. I suspected that with running with your arms low, at waist level would decrease run cadence due to making larger arm swings. The larger arm swings would require more energy, thus raising their heart rate. Those two things would decrease the pace they could sustain at any given heart rate. I decided to test this out on our treadmill. I set the treadmill at 9 MPH and a 1% incline to simulate out door running. Below is the video of the test and screen shots of the data within the video. If you don’t have time to watch this short video, the findings are below the video:
- 9 MPH at 1% grade with arms at correct height (about chest level at a 90 degree bend at the elbow) = 150 BPM and a cadence of 180-185
- 9 MPH at 1% grade with arms at waist = 155-156 BPM and a cadence of 165-170
- I could sustain the same HR of 155-156 BPM with the correct arm bend and swing at 9.2 MPH. That is about 10 seconds per faster per mile.
Correct run form (and arm position) from my triathlon days back in 2015. 
This arm bend angle is too big. Running with an arm bend a this angle will decrease cadence, increase heart rate, and slow you down.
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