Abstract
Diurnal and seasonal rhythmicity, entrained by environmental and nutritional cues, is a vital part of all life on Earth operating at every level of organization; from individual cells, to multicellular organisms, whole ecosystems and societies. Redox processes are intrinsic to physiological function and circadian regulation, but how they are integrated with other regulatory processes at the whole-body level is poorly understood. Circadian misalignment triggered by a major stressor (e.g. viral infection with SARS-CoV-2) or recurring stressors of lesser magnitude such as shift work elicit a complex stress response that leads to desynchronization of metabolic processes. This in turn challenges the system's ability to achieve redox balance due to alterations in metabolic fluxes (redox rewiring). We infer that the emerging 'alternative redox states' do not always revert readily to their evolved natural states; 'Long COVID' and other complex disorders of unknown aetiology are the clinical manifestations of such rearrangements. To better support and successfully manage bodily resilience to major stress and other redox challenges needs a clear perspective on the pattern of the hysteretic response for the interaction between the redox system and the circadian clock. Characterization of this system requires repeated (ideally continuous) recording of relevant clinical measures of the stress responses and whole-body redox state (temporal redox phenotyping). The human/animal body is a complex 'system of systems' with multi-level buffering capabilities, and it requires consideration of the wider dynamic context to identify a limited number of stress-markers suitable for routine clinical decision making. Systematically mapping the patterns and dynamics of redox biomarkers along the stressor/disease trajectory will provide an operational model of whole-body redox regulation/balance that can serve as basis for the identification of effective interventions which promote health by enhancing resilience.