HIIT Augments Muscle Carnosine in the Absence of Dietary Beta-Alanine Intake

Purpose Cross-sectional studies suggest that training can increase muscle carnosine (MCarn), although longitudinal studies have failed to confirm this. A lack of control for dietary β-alanine intake or muscle fibre type shifting may have hampered their conclusions. The purpose of the present study was to investigate the effects of high-intensity interval training (HIIT) on MCarn. Methods Twenty vegetarian men were randomly assigned to a control (CON; n=10) or HIIT (n=10) group. HIIT was carried out on a cycle ergometer for 12 weeks, with progressive volume (6-12 series) and intensity (140-170% lactate threshold [LT]). MCarn was quantified in whole-muscle and individual fibres; expression of selected genes (CARNS, CNDP2, ABAT, TauT and PAT1) and muscle buffering capacity in vitro (βmin vitro) were also determined. Exercise tests were performed to evaluate total work done (TWD), VO2max, ventilatory thresholds (VT) and LT. Results TWD, VT, LT, VO2max and βmin vitro were improved in the HIIT group (all P0.05). MCarn (in mmol·kg-1 dry muscle) increased in the HIIT (15.8±5.7 to 20.6±5.3; p=0.012) but not the CON group (14.3±5.3 to 15.0±4.9; p=0.99). In type I fibres, MCarn increased in the HIIT (from 14.4±5.9 to 16.8±7.6; p=0.047) but not the CON group (from 14.0±5.5 to 14.9±5.4; p=0.99). In type IIa fibres, MCarn increased in the HIIT group (from 18.8±6.1 to 20.5±6.4; p=0.067) but not the CON group (from 19.7±4.5 to 18.8±4.4; p=0.37). No changes in gene expression were shown. Conclusion In the absence of any dietary intake of β-alanine, HIIT increased MCarn content. The contribution of increased MCarn to the total increase in βmin vitro appears to be small. Corresponding Author: Guilherme Giannini Artioli, Av. Mello de Moraes 65 - Butanta, 05508-030, Sao Paulo, SP, Brazil. Phone: +55 11 3091-8783. Fax: +55 11 3813-5921, E-mail: artioli@usp.br Vitor de Salles Painelli, Guilherme Giannini Artioli, Bryan Saunders and Bruno Gualano have been financially supported by Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP grant numbers: 2013/04806-0, 2014/11948-8, 2016/50438-0, 2013/14746-4) and PROEX-CNPq. The authors declare that they have no competing interests. The results of the present study do not constitute endorsement by the American College of Sports Medicine. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 15 June 2018 © 2018 American College of Sports Medicine

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