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New research explores the link between long COVID and women’s ability to exercise. Artur Widak/NurPhoto via Getty Images
  • Long COVID or post-acute COVID syndrome is characterized by a multitude of symptoms that persist beyond the acute phase of 3–4 weeks after getting the SARS-CoV-2 virus.
  • Women hospitalized with COVID-19 are more likely to experience persistent deficits in cardiovascular and lung function than men in the months following discharge.
  • A new study found that even women with mild-to-moderate COVID-19 may experience slower declines in their resting heart rate after physical activity in the post-acute phase of the SARS-CoV-2 infection.
  • Such deficits in cardiovascular function during exercise are associated with reduced capacity for physical exercise and, potentially, activities of daily life.
  • Women presenting with specific long COVID symptoms, namely shortness of breath or joint or muscle aches, were also more limited in their ability to do a walking test than people who had had a SARS-CoV-2 infection but experienced no lingering symptoms.

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Although the majority of individuals recover within the first 3–4 weeks after contracting COVID-19, a considerable number continue to experience lingering symptoms for weeks or months after this initial or acute phase of the disease.

These symptoms, which people refer to collectively as long COVID or post-acute COVID-19, include shortness of breath, loss of smell and taste, brain fog, headaches, and fatigue.

Studies have shown that more than half of the individuals hospitalized with COVID-19 during the initial phase of the SARS-CoV-2 infection show persistent impairments in cardiovascular and lung function several months after discharge. Furthermore, women hospitalized with severe COVID-19 are more likely than men to present with such persistent deficits in cardiovascular and lung function after discharge.

Individuals may present with persistent symptoms during the post-acute phase of COVID-19, regardless of the severity of symptoms during the acute phase of the illness. The effects of mild-to-moderate COVID-19 on lung and cardiovascular function and, subsequently, on daily physical functioning during the post-acute phase is not well-understood.

Researchers at Indiana University, Bloomington, recently examined how mild-to-moderate COVID-19 affected exercise capacity or tolerance during the post-acute phase in women. Exercise tolerance or capacity refers to the ability of an individual’s cardiovascular system to sustain physical activity.

The researchers used an exercise test called the 6-minute walk test to assess the persistent effects of SARS-CoV-2 infection on cardiovascular function in women during the post-acute phase of the infection.

They found that women with COVID-19 who had mild-to-moderate illness during the acute phase showed a slower decline in their heart rate after the 6-minute walk test than the participants in the control group. This difference was more pronounced in women actively experiencing long COVID symptoms.

However, encouragingly, they found no statistically significant differences in a range of other measures, including pre- and post-test oxygen saturations, pre- and post-test heart rate, ratings of perceived exertion, and ratings of perceived breathlessness.

The study’s lead author, Dr. Stephen Carter, a professor at Indiana University, told Medical News Today: “A puzzling feature of post-acute COVID-19 syndrome is the variable presentation of symptoms that appear to be independent of initial illness severity. The present work shows even those with mild-to-moderate initial symptoms can be affected with underlying cardiac-related irregularities with the potential to affect exercise tolerance and/or activities of daily living.”

“It’s also plausible that lingering symptoms, particularly muscle/joint pain and/or shortness of breath, may trigger a maladaptive pattern that accelerates systemic deconditioning. However, further research is needed.”

Dr. Ziyad Al-Aly, chief of research and education service at Veterans Affairs St. Louis Health Care System, also spoke with MNT. Dr. Al-Aly, who was not involved with the study, said, “Studies like this are important to help us understand why some people with long COVID experience profound exertional fatigue that may limit their ability to exercise and their ability to carry out activities of daily living.”

The study appears in the journal Experimental Physiology.

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The study included 29 women who had experienced mild or moderate illness due to COVID-19. These women had received a positive SARS-CoV-2 diagnosis at least 4 weeks prior to the study, with the average time of diagnosis being 94 days before the study. The control group consisted of 16 women who had never tested positive for a SARS-CoV-2 infection.

Out of the 29 participants in the test group, 17 women reported experiencing at least one long COVID symptom at the time of the study. These long COVID symptoms included shortness of breath, fatigue, cough, muscle or joint pain, loss of smell or taste, and skin irritation.

The researchers administered pulmonary function tests to assess various aspects of lung function. They found that the women who had tested positive for SARS-CoV-2 exhibited reduced total lung capacity compared with those in the control group.

The researchers then evaluated changes in cardiovascular function during and after the 6-minute walk test. The test measures the distance that participants walk in 6 minutes at their normal pace, and researchers use it to assess exercise tolerance. The team adjusted the results for age, sex, and body mass index (BMI) to prevent these variables from influencing the test results.

There was no significant difference between the distances that the two groups covered during the test.

However, women with SARS-CoV-2 who experienced shortness of breath or joint or muscle pain had a lower adjusted distance value than those with SARS-CoV-2 who did not experience these long COVID symptoms.

The researchers assessed the blood pressure, heart rate, and blood oxygen or oxygen saturation levels before and immediately after the 6-minute walk test. They calculated the heart rate response during exercise by subtracting the heart rate at rest from the heart rate after the completion of the test.

The heart rate response during exercise is a measure of cardiovascular function, with a lower heart rate response being a predictor of reduced exercise capacity and cardiovascular disease-associated mortality.

The women in the SARS-CoV-2 group showed a lower heart rate response than those in the control group.

Moreover, the participants in the SARS-CoV-2 group who reported shortness of breath as a long COVID symptom at the time of the study had a lower heart rate response during the test than those in the SARS-CoV-2 group who did not have this symptom.

The researchers also measured heart rate recovery, which is another indicator of cardiovascular health and all-cause mortality.

Heart rate tends to drop immediately after strenuous exercise. Heart rate recovery measures the decrease in heart rate after the cessation of exercise. Specifically, heart rate recovery quantifies the decrease in heart rate at a predefined time interval — generally 1 minute — from the end of the physical activity.

In the current study, the researchers measured the participants’ heart rate at the end of each minute during the 5-minute recovery period after the 6-minute walk test.

The SARS-CoV-2 group participants showed a less significant decrease in heart rate at 1 minute after the completion of the test than those in the control group. This suggests that the decline in heart rate occurred more gradually in the women in the SARS-CoV-2 group. Such a delay in heart rate recovery is associated with reduced exercise capacity.

Furthermore, women in the SARS-CoV-2 group who exhibited specific long COVID symptoms at the time of the study had decreased heart rate recovery compared with the SARS-CoV-2 group participants without these symptoms.

Specifically, women in the SARS-CoV-2 group with symptoms such as fatigue, loss of taste or smell, joint and muscle aches, or shortness of breath had decreased heart rate recovery compared with women who had not had SARS-CoV-2.

“A lot of long COVID-19 patients are placed into rehabilitation programs that are designed for non-COVID-19 patients. These programs may not be suitable for long COVID patients. It is important to understand that people with long COVID need programs designed for them (pacing, etc.). Findings from this study and others should be taken into account when designing rehabilitation programs for people with long COVID,” said Dr. Al-Aly.

Dr. Carter noted: “SARS-CoV-2 participants and [people without the infection] were matched for age, BMI, smoking status, and history of cardiopulmonary disease. As such, we have better assurance that reported differences were attributed to SARS-CoV-2, as opposed to another comorbidity.”

“A strength of the work is that comparisons were performed among women — who appear to be susceptible to persistent SARS-CoV-2-related symptoms — during and following a 6-minute walk test.”

Dr. Carter acknowledged that the study had a few limitations. He said: “Indeed, the 6-minute walk test is a widely used clinical tool that offers insight into exercise capacity and walking autonomy. However, it should be noted we cannot disregard the possibility of undiagnosed pulmonary abnormalities and/or autonomic dysfunction that existed prior to a SARS-CoV-2 infection. Additionally, it is conceivable some controls may have had an asymptomatic SARS-CoV-2 infection and/or a previous false-negative diagnostic test for SARS-CoV-2.”

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