Exercise and functional integrity in non-disease and disease states during human ageing: the relevance of VO_2max

Maximal oxygen update (VO_2max) is the acknowledged biomarker for cardiorespiratory fitness and global physiological function. It is affected by levels of exercise/physical activity and declines with increasing age even in older exercisers. Here in this conceptual paper we suggest that exercise can facilitate age-appropriate VO_2max levels across a spectrum of physiological phenotypes ranging from disease-free, through minor to more major diseases. The absence of disease during ageing is rare and requires a lifestyle of physical activity, mental wellbeing, a well-balanced nutritious diet, whilst maintaining a body weight appropriate to sex and age. The maintenance of optimal, age-adjusted function over a lifetime should be viewed as an ordered, integrated decline in physiological processes. However, in the absence of this lifestyle, patho-physiological processes take over and the end result is inevitably a lifestyle disease. Disease processes during ageing can be generally divided into those that arise largely because of lifestyle (e.g. cardiovascular disease, obesity and type 2 diabetes) and those that relate to other causes (genetics, environment etc.). If, in either situation cardio-respiratory fitness can be preserved either by exercise alone or in combination with medical interventions, then function, optimal for age, should be maintained. This article discusses concepts pertaining to exercise, optimal physiological function as reflected in the biomarker VO_2max, as well as the interplay with ROS in the presence of non-disease and disease states during ageing.