Deconditioning is a term used to describe the physical decline a person might experience following a period of inactivity. It has long been recognised, but has previously been associated with prolonged periods of immobility or hospitalisation resulting from injury or illness. As we come out of the Covid-19 pandemic and the associated periods of lockdown and shielding the more vulnerable, there is evidence that some of the population are suffering the effects of deconditioning. It is apparent that this may be with or without coexisting medical conditions and needs to be considered as an additional or stand-alone diagnosis where symptoms exist, or where worsening of an underlying medical condition could be as a result of deconditioning. This article considers the causes and effects of deconditioning, its impact on physical and mental health, and how we can approach reconditioning programmes through health and society.