Although the SARS-CoV outbreak of 2003 resulted in far fewer infection rates than COVID-19, the similarities between the two infectious diseases signify that we may learn much about the latter by studying the former . Both diseases exhibit a hospitalization rate of approximately 30%, with about 20% of the hospitalized population entering an intensive care unit (ICU) . Especially in patients severely afflicted by SARS-CoV infection, impairment of physical function could be observed up to two years after the initial infection . This damage is caused by various factors related to the disease and its treatment. As a result, it is useful to understand how SARS-CoV affects physical function and fitness to determine the best path for the rehabilitation of COVID-19 patients.
SARS-CoV patients reported decreased exercise capacity in comparison to the general population [2, 3]. While one study found the exercise capacity of SARS-CoV survivors to be lower than that of the general population, the degree to which survivors were less fit was not large . Additionally, those researchers acknowledged an uncertainty concerning how much the patients’ previous level of fitness contributed to these measurements . However, another study observed that the distance that survivors could walk had significantly decreased a year after infection . One study tracking SARS-CoV patients every three months for two years following infection onset reported a similar decrease in walking capability . Although patients’ results on the six-minute walk test improved significantly in the first few months after recovery, most patients were still not fully recovered at the two-year mark . Evidently, these results suggest that SARS-CoV patients’ decrease in physical function is not negligible.
One common difficulty exhibited by SARS-CoV patients was aerobic capacity. One study observed mild pulmonary abnormalities in 50% of the study’s patient population three months after hospital discharge . 41% of patients in that same study also reported maximum aerobic capacities below the normal range . In another study, 24 months after initial infection, one half of participants reported possible impairment in the intra-alveolar diffusion pathway . However, this study was limited by a small sample size . Despite this trend of mildly diminished cardiopulmonary performance, another study found the health-related quality of life (HRQQL) performance of SARS-CoV patients to be significantly impaired, suggesting the presence of additional sources of reduced physical function .
Other factors that may have been responsible for SARS-CoV’s patients’ reduced exercise capacity include muscle weakness and physical deconditioning . Both of these symptoms could be attributed to prolonged hospitalization, considering their particular prevalence in survivors of severe cases of the disease . They may also be due to critical illness-associated polyneuropathy, myopathy, or steroid myopathy . Considering how severe cases of coronavirus diseases are more common in patients with comorbidities (examples being cardiovascular disease and diabetes), the combined effect of SARS-CoV and these comorbidities could have exacerbated patients’ mobile disability . Lastly, chronic fatigue, reported in 40.3% of survivors in one study, could also contribute to decreased physical ability .
Because researchers were not able to isolate a singular causal pathway between SARS-CoV and diminished physical function, there was no clear-cut path to rehabilitation in physically limited SARS-CoV patients. . Accordingly, medical practitioners must study this wealth of information when considering how best to aid COVID-19 patients restore their physical function, both during the course of infection and beyond.
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 H. M-C. Lau et al., “The Impact of Severe Acute Respiratory Syndrome on the Physical Profile and Quality of Life,” Archives of Physical Medicine and Rehabilitation, vol. 86, no. 6, p. 1134-1140, June 2005. [Online]. Available: https://doi.org/10.1016/j.apmr.2004.09.025.
 M. H. B. Lam et al., “Mental Morbidities and Chronic Fatigue in Severe Acute Respiratory Syndrome Survivors,” Archives of Internal Medicine, vol. 169, no. 22, p. 2142-2147, December 2009. [Online]. Available: https://doi.org/10.1001/archinternmed.2009.384.