Two different activity trackers for tracking physical activity in patients with pulmonary arterial hypertension (PAH) yielded discordant results, according to a new study published in European Heart Journal.

“Activity trackers for clinical trials and remote monitoring are appealing as they provide objective data outside of the clinic setting,” Lachant et al wrote. In addition, scientists believe they have the potential to improve the management of chronic diseases and provide exploratory, or even primary, endpoints in clinical research. 

The research team decided to compare 2 different research-grade accelerometers by placing them strategically at 2 different parts of the body: 1 on participants’ nondominant hand, and the other on the chest/leg. They would then evaluate the physical activity measurements provided by these devices and compare them to established metrics in PAH, such as risk assessment and hemodynamics.

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Their hypothesis was that chest-based devices would correlate with PAH clinical metrics more closely due to fewer irrelevant movements (such as those of the wrist, for example).

Lachant and colleagues conducted their study on 22 participants with PAH using the Actigraph GT9X Link (on the nondominant wrist) and MC10 Biostamp nPoint (on the chest and leg). Participants were required to wear the devices for a total of 5 to 10 days, allowing researchers ample time to track daily physical activity and daily total steps.

Read more about PAH patient education 

Participants wore the accelerometers for more than 12 hours per day. If participants had right heart catheterization within 7 days of activity monitoring, the participants’ hemodynamic data was compared to activity data. (Right heart catheterization was only performed if indicated).

“We report significant differences between the metrics (especially activity time) measured with wrist as compared to chest based activity trackers in a diverse group of PAH patients,” the researchers wrote.

The data between the Actigraph and the MC10 devices did not match: the average activity time measured by the Actigraph was significantly higher (251 +/- 25 minutes), compared to the MC10 (113 +/- 18 minutes). In addition, hemodynamics data obtained from participants who had right heart catheterization performed within 7 days of the study did not correlate with daily steps or activity time. 

This study exposed the flaws of monitoring physical activity purely through the use of wearable devices.

“Further studies are needed in determining what each device is actually measuring through controlled manipulation, the best type of device for a given measure, optimal wear time for assessment (as this could significantly influence measurements), and adjusted thresholds for chronic diseases,” the researchers concluded.


Lachant D, Light A, Hannon K, Abbas F, Lachant M, White RJ. Comparison of chest and wrist based actigraphy in pulmonary arterial hypertension. Eur Heart J. Published online November 2, 2021. doi:10.1093/ehjdh/ztab095