Concurrent Training and Intermittent Fasting Reduce Transverse Cross-sectional Area of Cardiomyocytes and Body Mass in Wistar Rats

Henrique Izaias Marcelo^1,2*Marina Politi Okoshi³Letícia Estevam Engel⁴Wanderson da Silva Rosa⁵Paulo Henrique Aleixo^6,7Guilherme Akio Tamura Ozaki⁷Everton Alex Carvalho Zanuto⁶Luiz Carlos Marques Vanderlei⁸Francis Pacagnelli^4,9Robson Chacon Castoldi¹⁰

• ¹University of São Paulo (USP), Institute of Biomedical Sciences, Department of Physiology and Biophysics, Sao Paulo, Brazil
• ²University of Western São Paulo (UNOESTE), Department of Physical Education, Presidente Prudente, Brazil
• ³Paulista State University (UNESP), Postgraduate Program in Pathophysiology in Internal Medicine., Botucatu, Brazil
• ⁴University of Western São Paulo (UNOESTE), Postgraduate Program in Animal Science, Presidente Prudente, Brazil
• ⁵University North of Paraná (UNOPAR), Postgraduate Program in Physical Exercise in Health Promotion, Londrina, Brazil
• ⁶University of Western São Paulo (UNOESTE), Department of Physical Education., Presidente Prudente, São Paulo, Brazil
• ⁷Campinas State University (UNICAMP), Postgraduate Program in Animal Science,, Campinas, Brazil
• ⁸Paulista State University (UNESP), Postgraduate Program in Movement Sciences, Presidente Prudente, Brazil
• ⁹University of Western São Paulo (UNOESTE), Postgraduate Program in Health Sciences, Presidente Prudente, Brazil
• ¹⁰5- University North of Paraná (UNOPAR), Postgraduate Program in Physical Exercise in Health Promotion., Londrina, Brazil

Methods: This study identified the alterations caused by concurrent training and intermittent fasting on the myocardium of rats. In total, 39 adult male Wistar rats were used, divided into four groups: control (C [n = 12]), fasting control (FC [n = 11]), training (T [n = 8]), and fasting training (FT [n = 8]). The critical load test was performed to evaluate and determine the intensity of effort in aerobic training (AT) (swimming). The resistance training protocol (RT) (anaerobic) consisted of four series of 10 jumps, with overload corresponding to 50% of the body mass of each animal, and 1 minute of rest between each series. The concurrent training (CT) was composed of a protocol of AT and RT in the same session. The intermittent fasting period was 12/12 hours. At the end of the experiment, the animals were weighed to obtain the Lee index; heart weight was verified, and tissue samples were collected for further histological analysis. After obtaining the data, the Shapiro-Wilk test was performed, followed by a two-way analysis of variance (ANOVA) with Tukey's post-test for the variables measured at the end of the experiment. Results: For the variables body mass, feed consumption, and the anaerobic threshold, the FC group showed a greater decrease in the Lee index ([0.28±0.00] p <0.05) in relation to the other groups. There were no significant alterations (p>0.05) in relation to heart weight, fractal dimension, and anaerobic threshold (AnT); finally, both the T and the FT groups presented a significant decrease ([T: (277.3 ± 119.3 / FT: 310.5 ± 148.8] p<0.05) in the transverse cross-sectional area of the cardiomyocytes, when compared to the control groups.The practice of concurrent training for a period of 4 weeks precipitated a decrease in the transverse cross-sectional area of the cardiomyocytes of Wistar rats. Furthermore, when combined with intermittent fasting, concurrent training not only led to a reduction in the transverse cross-sectional area of the cardiomyocytes but also resulted in a decrease in body mass compared to the isolated concurrent training model.