The topicality of the research is conditioned by the social and pedagogic, scientific and theoretical, and scientific and methodical aspects. With regard to this, the paper is aimed at revealing the dependence of the teacher's overall work capacity on the development of his/her professional expertise. The leading methods in studying this problem are theoretical and experimental ones that allow viewing the problem comprehensively. The paper presents the ways of evaluation of indices characterizing the condition of physiological, psychological and emotional components of the functional system that determine the level of overall work capacity of teachers and development of their professional expertise. The materials of the paper are of practical value for the heads of professional education organizations designing the pedagogues' professional development.