Working out in the COVID aftermath: How intense can one go?

Outpatients with post-COVID condition (PCC) generally tolerated exercise without significant worsening of symptoms or decline in aerobic performance after 48 hours. However, they had lower muscle strength and aerobic capacity than controls, and even showed signs of POTS* and myopathy in a randomized crossover trial.

Between individuals with PCC and controls, there were no differences in fatigue worsening after exercise, be it HIIT, MICT, or ST** (mean VAS*** ranks, 29.3 vs 28.7; p=0.08, 31.2 vs 24.6; p=0.09, and 31 vs 28.1; p=0.49, respectively). “While this indicates no general symptom exacerbation after exercise, it should be noted that changes in fatigue, pain, and concentration from baseline to 48 hours after exercise varied among individuals,” the researchers said.

Compared with controls, patients with PCC reported worse muscle and joint pain after HIIT (mean VAS ranks, 33.4 vs 25; p=0.04 [muscle] and 33.6 vs 24.9; p=0.009 [joint]), more concentration difficulties after MICT (mean VAS ranks, 33 vs 23.3; p=0.03), and greater increase in muscle soreness after ST (mean VAS ranks, 32.1 vs 20.9; p=0.007 [vs HIIT] and 33.1 vs 17.9; p<0.001 [vs MICT]). [JAMA Netw Open 2024;doi:10.1001/jamanetworkopen.2024.4386]

“Nonetheless, the observation that nonhospitalized patients with PCC could tolerate various physical activities without escalation of symptoms is important,” they stressed. “It implies that physical activity tailored for patients on an individual basis could be an essential component in rehabilitation to enhance physical function and counteract muscle deconditioning.”

Physiologic function

Patients with PCC had a 14-percent reduced stroke volume (mean difference, -2.6 mL; p=0.02) and a 5-percent smaller left ventricular diameter vs controls (mean difference, -9.7 mm; p=0.03).

Blood and plasma volumes were also numerically lower in patients with PCC than controls (-5.2 mL/kg; p=0.12 [blood] and -3.4 mL/kg; p=0.09 [plasma]). “[This may be] due to the reduced levels of high- and moderate-intensity physical activity, which are associated with decreased blood volume and venous return affecting left ventricular diameter and stroke volume, and to increased resting heart rate,” they explained.

Moreover, head-up tilt testing showed POTS in two patients with PCC and borderline POTS in two more; the control arm had none. “While deconditioning can partially explain the observed orthostatic intolerance … we cannot exclude the possibility that impaired autonomic function after viral infection … led to the exaggerated heart rate response,” they said. [Nat Rev Cardiol 2023;20:281-282; Innov Aging 2022;6:302-303; Heart Rhythm 2022;19:1880-1889]

Patients with PCC spent 43-percent less time in MVPA^# (mean difference, -26.5 min/d; p=0.001) and showed 19-percent less variability during deep breathing than controls (mean difference, -5.7 percent; p=0.05), suggesting parasympathetic nervous system involvement. [Sci Rep 2023;13:8251s]

Arterial stiffness was greater in patients with PCC vs controls, as indicated by the 8.3-percent higher aortic pulse wave velocity (mean difference, 0.7 m/s; p=0.04). According to the researchers, the vascular involvement may have been driven by mechanisms such as inactivity, direct viral damage, or cytokine-mediated effects on the vascular endothelium. [J Am Heart Assoc 2017;6:e005974; Acta Pharmacol Sin 2023;44:695-709]

About two-thirds (62 percent) of patients with PCC showed myopathic signs as opposed to only one in the control arm. “Our electromyography results suggested myogenic-derived rather than neurogenic causes of the myopathies in patients with PCC, evident in characteristics such as early recruitment of small, short-duration, frequent, polyphasic MUPs^##,” the researchers explained. [Clin Neurophysiol 2019;130:1688-1729]

Cautious exercise rehab recommended

“[The WHO defines PCC as the] constellation of symptoms that patients continue to experience after ≥3 months, [affecting about] 10–20 percent of those infected with SARS-CoV-2, including nonhospitalized individuals,” the researchers said. It is mostly characterized by symptoms such as persistent fatigue, myalgia, dyspnoea, and neurologic or cognitive dysfunction, which could worsen following physical exertion. [EClinicalMedicine 2022;55:101762; https://www.who.int/news-room/questions-and-answers/item/coronavirus-disease-(covid-19)-post-covid-19-condition; https://iris.who.int/bitstream/handle/10665/365580/WHO-2019-nCoV-clinical-2023.1-eng.pdf]

“Recommendations currently advise against exercise in this population to prevent symptom worsening; however, prolonged inactivity is associated with risk of long-term health deterioration,” they stressed.

Sixty-two nonhospitalized patients (mean age 47 years, 76 percent women) without concomitant diseases and with persistent (≥3 months) symptoms after SARS-CoV-2 infection were recruited in Sweden from September 2022 to July 2023. Half had PCC while the other half comprised the healthy control group. All participants completed three exercise sessions (HIIT, MICT, ST) in a randomized, balanced order with a washout period of about 2 weeks between sessions.

“It is plausible that our results represent a phenotype indicative of inactivity coupled with primary peripheral tissue damage and neurophysiologic changes leading to further difficulty in performing strenuous activity,” said the researchers.

“However, given that exercise was generally well tolerated, guidelines cautioning against exercise in similar populations may need to be revised. It seems advisable to cautiously incorporate exercise into rehabilitation protocols and adjust the intensity progressively, considering patients’ symptoms and abilities,” they added.

They cautioned however that the findings should not be generalized to all patients with PCC.