Abstract
The purpose of this article is to provide a follow-up review of the impact of the SARS-CoV-2 Disease or Coronavirus Disease 2019 (COVID-19) pandemic on human health and the role of physical activity (PA) during the 5-year pandemic. We aim to cover the immune system, the cardiopulmonary system, the musculoskeletal system, and the central nervous system (brain function), particularly among older adults, college students, and individuals with post-acute sequelae of COVID-19 (Long-COVID). The COVID-19 pandemic has given us many lessons, learned from the death of six million lives and tremendous disturbance to human life. First, we need to continue to investigate cellular and molecular mechanisms that mediate various organistic failures resulting from the viral infection. Such investigations are the only way to completely understand the etiology of the diseases and to develop new drugs and vaccines. The molecular pathways that transmit the signals of viral infection to each organ system are different requiring both basic and clinical research. Available evidence suggests that mitochondrial dysfunction, reduced microcirculation and latent immune activation play a major role, eventually impairing cardiovascular tolerance and peripheral bioenergetics. Second, the COVID-19 pandemic has manifested major disturbances to human lifestyles with reduced PA and exercise standing out as a major factor. Conversely, physical inactivity due to social confinement and mental/psychological stresses has been clearly linked to intensified pathogenic symptoms and amplification of adverse effects on multiple physiological systems. If not intervened, this interaction can lead to Long-COVID, a dangerous futile circle to cause systemic failure. Finally, the COVID-19 pandemic has exerted differential impacts on different populations. Thus, the strategy to develop and conduct to cope with the negativity of pandemic needs to be specific, flexible and tailored to fit different patient populations.