Persistent Effects Of Covid-19 On Oxygen Responses To Low Intensity Exercise

Acute infection with the SARS-CoV-2 virus results in long-term, persistent symptoms in ~50% of patients. Persistent symptoms include changes in pain, fatigue, cognition, physical activity, and neurologic function, that impact activities of daily living. Oxygen response (V̇O2) at low intensities, rather than V̇O2 during maximal exercise, may provide insight into the differences in physical function in those with COVID. PURPOSE: To determine whether people who were previously infected with COVID have altered oxygen response during low to moderate intensity exercise. METHODS: 88 COVID-19 survivors (COV, 60 females), 2-23 months post infection (8.0 ± 2.4 months), were categorized into 2 different severity groups (CV1 and CV2) based on the number of symptoms reported at the time of acute COVID illness. CV1 had 0 to mild symptoms at time of testing, and CV2 had moderate to severe symptoms according to a symptom checklist. 42 Controls (CON, 29 females) were also recruited. Baseline spirometry and V̇O2 during cardiopulmonary exercise test (CPET) were measured. CPET was performed using a submaximal YMCA cycle protocol with analysis specific to the 3-minute warm-up at the 1st 25 W workload. RESULTS: At rest, heart rate, oxygen saturation, blood pressure, and pulmonary indices did not differ between any of the groups. During 25 W cycling, however, V̇O2 was increased more at minute 1 (p = 0.048) and minute 2 (p = 0.040) for CV2 compared to CON and CV1. CV2 group had higher body fat percentage (p = 0.002), and lower average moderate to vigorous physical activity (AMVPA, p = 0.001). CONCLUSIONS: The greater increases in oxygen uptake in more severely affected COVID-19 survivors at least 2 months post infection suggest an increased oxygen response to low-level exercise which may affect activities of daily living. More investigation is required to understand the cause for the altered oxygen uptake during low-level exercise and strategies to inform best practices in rehabilitation.