Defining a molecular portrait of physical fitness

Abstract

To most individuals, the concept of fitness tends to conjure up mental images of physical attributes such as muscular definition or low bodyweight. However, while physical fitness (e.g., body weight, adiposity) is an important component of overall health, there are many “unseen” physiological and biological fitness alterations to the human body that have a far-reaching impact on health and wellness. Over the years, there have been many studies investigating the physiological implications, benefits, and consequences of physical fitness [1]. There are a number of important physiological adaptations, which occur with increasing aptitude in physical fitness. These adaptations include, but are not limited to, greater cardiorespiratory capacity/efficiency, denser bone structure, higher basal metabolic rates, and lower levels of adiposity [2–4]. Furthermore, each adaptation is linked to improved mortality and reduced risk of acute and chronic illnesses. However, though mostly beneficial, these unseen physiological fitness changes may be so varied depending on the individual that they can cause challenges for healthcare providers [5, 6]. Prevention and management of disease, as well as therapeutic dosing, are directly affected by the fitness level of an individual. Therefore, defining the fitness status of an individual at a molecular level, not just by determining physical parameters of fitness, should result in better healthcare and enhanced well-being of an individual. For example, although therapeutic dosing is, in general, determined based on the total body weight of an individual, studies have demonstrated that more physically fit individuals, with more lean mass and less adiposity, can clear pharmaceuticals faster than sedentary individuals with the same total body weight [7, 8]. Dosage decision making may be better tailored to an individual's need in the future by taking into account his/her fitness level. In that regard, the availability of molecular markers of fitness should allow for more precise therapeutic dosing as compared to the traditional method of basing it on total body weight. The ability to rapidly determine the aptitude and the level of physical fitness, through molecular screening methods, has implications in many different fields, those ranging from healthcare [2, 5, 6, 9] to athletics [3] and to the military [10, 11]. To this end, it is necessary to discover and investigate molecular markers which are robust, can be observed at either elevated or lowered levels after short or prolonged exercise(s) regimes or during sedentary periods, and are accurate indicators of the physical fitness and lifestyle of an individual. Furthermore, it will also be necessary to develop point-of-care devices and corresponding analytical methods to make analysis of these molecular markers as simple and cost effective as possible. The aim of this article is to provide information that guides in the selection, detection, and future usage of molecular markers of physical fitness.