Participants
Twenty male and female CrossFit-trained practitioners were initially enrolled in this study and randomly allocated to the double-blinded treatment sequence (SB + CHO → PLA + CHO or PLA + CHO → SB + CHO) in a balanced design. There was one drop-out from the study, due to personal reasons (PLA + CHO → SB + CHO sequence). A total of 19 participants aged 37 ± 8 years and of mean body mass 75.1 ± 13.1 kg, completed the whole study protocol and were included in the analyses (Table Baseline characteristics of studied group.Data are mean ± SD. The inclusion criteria were: good general health, a valid and up-to-date medical certificate that confirmed the athlete’s ability to practice sports, at least 4 years of training experience and participation in a minimum of four CrossFit workout sessions a week. The exclusion criteria were: current injury, health-related contraindication, declared general feeling of being unwell and unwillingness to follow the study protocol. The entire protocol for each participant lasted 4 weeks. All the study procedures were performed in the sport club in which participants practice CrossFit on regular basis (Lubin, Lubuskie Province, Poland).The study protocol was reviewed and approved by the local institutional review board (Bioethics Committee at Poznan University of Medical Sciences, reference number: 1000/18 of 11 October 2018), and registered at ClinicalTrials.Gov (NCT03810404, 18/01/2019). Written informed consent was obtained from all participants before their participation in the study began. All procedures were conducted in accordance with the ethical standards of the 1975 Declaration of Helsinki. The study complies with the CONSORT statement for randomized trials, as shown in Fig. A flow chart of the study design.G*Power software (version 3.1.9.4, Universität Düsseldorf, Germany) was used to calculate the sample size required to obtain a power of approximately 80% (α = 0.05) and large effect size partial eta squared 0.14