。
On the characteristics of swimmers' respiratory function.
Literal
Swimmer [genitive-の] respiratory-function [genitive-の] characteristics [about-について].
A paper or presentation title. Title-register Japanese routinely drops verbs and copulas, relying on particles and noun-heavy phrasing. ~について ('about X,' 'concerning X') is the standard phrase for 'on (the topic of) X' in paper titles — Japanese titles of academic papers or chapters often end in について or に関して without a following noun, leaving the 'report,' 'study,' or 'paper' implicit. The period at the end is a title-style termination rather than a sentence period. 泳者 is an unusual word for 'swimmer' — the more common 水泳選手 or 泳ぐ人 would be used in non-technical writing.