Adaptations, safety factors, limitations and trade-offs in human exercise performance

Objectives
This review will describe how human exercise performance at the high- est level is exquisitely orchestrated by a set of responses by all body systems related to the evolutionary adaptations that have taken place over a long history. The review will also describe how many adaptations or features are co-opted (exaptations) for use in different ways and have utility other than for selective advantage.
Methods
A review of the literature by relevant search engines and reference lists in key published articles using the terms, performance, limitations, regulation, trade-offs as related to exercise, indicates that there are at least three areas which could be con- sidered key in understanding the evolutionary basis of human exercise performance.
Results
First, there is a basic assumption that exaptations have limitations or capaci- ties which cannot be exceeded which in turn will limit our physical performance. Second, it is thought that some biological systems and tissues have additional capac- ity which is rarely fully accessed by the organism; referred to as a safety factor. Third, there are biological trade-offs which occur when there is an increase in one trait or characteristic traded for a decrease in another.
Conclusions
Adaptations have resulted in safety factors for body systems and tis- sues with trade-offs that are most advantageous for human performance for a specific environment.