# ASSOCIATIONS BETWEEN HEART RATE AND PHYSICAL ACTIVITY IN PEOPLE WITH POST-COVID-19 CONDITION ACCOUNTING FOR MYALGIC ENCEPHALOMYELITIS/CHRONIC FATIGUE SYNDROME SYMPTOMS

## TL;DR

People with post-COVID-19 condition experience more tachycardia during low activity than during moderate activity, even when accounting for chronic fatigue symptoms.

## Contribution

This study is the first to explore heart rate and physical activity dynamics in post-COVID-19 condition while adjusting for ME/CFS symptoms.

## Key findings

- Heart rate increased with higher physical activity levels from sedentary to moderate-to-vigorous.
- Tachycardia occurred less during moderate activity compared to sedentary periods, even after adjusting for ME/CFS symptoms.
- Participants with post-COVID-19 condition showed more tachycardia during minimal activity.

## Abstract

Tachycardia after mild activity or during rest is a common complaint among people with post-COVID-19 condition (PCC). Understanding the relationships between heart rate (HR) and physical activity (PA) in this population is crucial for developing appropriate rehabilitation protocols.

To investigate the associations between HR and PA in individuals with PCC, accounting for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) symptoms.

Observational study.

Sixteen adults with PCC (81% females, mean age 51 ± 12 years).

Participants were instructed to use 2 wearable devices (Garmin smartwatch and ActiGraph accelerometer) during waking hours over 4 days while performing daily activities. Average HR, percentage of time in tachycardia (time with HR > 100 bpm), and daily step count were assessed. The accelerometer counts per minute was used to categorize daily PA as sedentary, light intensity, and moderate-to-vigorous (MVPA).

Participants wore the watches and accelerometers for a mean of 11.36 ± 2.60 and 12.51 ± 1.94 h per day, respectively. Average daily HR increased with increasing PA levels from sedentary to MVPA. However, the percentage of time in tachycardia was significantly lower during periods of MVPA compared with sedentary periods, even after adjusting for ME/CFS symptoms.

Individuals with PCC in our study experienced more tachycardia during periods of minimal physical activity compared with periods categorized as MVPA.

This study explored the associations between heart rate and physical activity in individuals with post-COVID-19 condition accounting for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome symptoms. Tachycardia (elevated heart rate) during mild activity or at rest is common among those with post-COVID-19 condition, and understanding this relationship is important for developing effective rehabilitation strategies. The study involved 16 adults with post-COVID-19 condition (81% females, average age 51 years) who wore a Garmin smartwatch and an ActiGraph accelerometer for 4 days to track their heart rate and daily physical activity. The study found that heart rate increased with higher levels of physical activity, from sedentary to moderate-to-vigorous physical activity. However, the percentage of time spent in tachycardia was significantly lower during moderate-to-vigorous physical activity compared with sedentary periods, even after adjusting for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome symptoms. The results suggest that individuals with post-COVID-19 condition experience more tachycardia when engaging in minimal physical activity, highlighting the importance of understanding heart rate-physical activity dynamics for better managing post-COVID-19 condition rehabilitation.