Physiological adaptations to training in competitive swimming: a systematic review.

The purpose of this systematic review was to summarize longitudinal evidences on swimming physiology and draws implications for daily practice. A computerized search of databases according to the PRISMA statement was employed. Studies were screened for eligibility on inclusion criteria: (i) present two testing points; (ii) on swimming physiology; (iii) using adult elite swimmers; (iv) not case-studies or with small sample sizes. Two independent reviewers used a checklist to assess the methodological quality of the studies. 34 studies were selected for analysis. Studies were gathered into five main categories: blood composition (n=7), endocrine secretion (n=11) muscle biochemistry (n=7), cardiovascular response (n=8) and energetic profile (n=14). The mean quality index was 10.58 ± 2.19 points demonstrating an almost perfect agreement between reviewers (K = 0.93). It can be concluded that the mixed findings in the literature are due to the diversity of the experimental designs. Micro variables obtained at cellular or molecular level are sensitive measures that suggest overtraining signs and health symptoms. The improvement of macro variables (i.e. main physiological systems) is limited and may depend on the athletes’ training background and experience