ABC | Volume 110, Nº4, April 2018

Original Article Winter et al High-intensity training after AMI Arq Bras Cardiol. 2018; 110(4):373-380 At the end of the training program, the LT test was repeated aiming to evaluate the effect of the training. When pre- and post-training results were compared in the ITG and CTG (intragroup comparison), the LT graph moved to the right (Graphs 1 and 2), indicating a positive effect of the training, i.e., the animals can tolerate a higher training load with similar energy consumption. Anaerobic threshold has been used as a measurement of physical fitness to assess the effects of training in patients with CVD and in healthy subjects, acting as a sensitive indicator of aerobic conditioning. 15 In addition, measurement of LT establishes an effective training intensity in terms of aerobic metabolic dynamics of active muscles. This training effect behavior has a high practical applicability, as improvements in physical fitness may be detected during the training sessions. 16 However, between-group comparisons did not show any significant differences between ITG and CTG (Table 4), which indicates that both models had a similar effect in this sample. Besides, as expected, no differences were found between the results before and after the training period in the CG, as favorable effects of training cannot be produced during resting condition. Also, Table 1 shows significant differences between the training groups (CTG and ITG) and the CG in two-by-two comparisons. The fact that the ITG and the CTG showed similar results after the training period may be justified by studies 17,18 that support that there is no evidence of the superiority of one exercise prescription model over another one in improving aerobic conditioning. However, the study by Vona et al. 11 concluded that both methods or their combination are efficient and safe to correct endothelial dysfunction in recent AMI. Schjerve et al. 12 demonstrated that high‑intensity interval exercise was more effective in improving endothelial function and in reducing cardiovascular risk than moderate‑intensity continuous exercise. It is worth pointing out that high-intensity training tends to have a better effect on maxVO 2 and lactate tolerance than on anaerobic threshold (or LT); in contrast, continuous training improves LT, but not necessarily peak VO 2 . Since the aim of the incremental test in this study was to determine the LT and thereby establish the optimal training load, changes in maximum physical capacity were not evaluated, which could be favored by the interval training. Since interval training has been recently investigated in cardiac rehabilitation programs and periodization of this type of exercise has not been well defined, it is possible that changes in the number of training repetitions and resting periods may produce more positive and favorable results than continuous training. 19 We believe that the same training prescription used for the animals in the present study may be performed for post-AMI patients in rehabilitation programs. Conclusion This study demonstrated that high-intensity training, above the LT, did not worsen endothelial function, and was safe for post-AMI rats. Both training methods proposed improved cardiorespiratory fitness in the animals. Study limiation One possible limitation of this study was the use of a portable lactate analyzer instead of a micropipette. Author contributions Conception and design of the research: Winter SCN, Macedo RM, Meira LF, Guarita-Souza LC; Acquisition of data: Winter SCN, Francisco JC, Santos PC, Lopes APS, Meira LF; Analysis and interpretation of the data: Winter SCN, Macedo RM, Santos PC, Lopes APS, Guarita‑Souza LC; Statistical analysis: Winter SCN, Macedo RM, Guarita‑Souza LC; Writing of the manuscript: Winter SCN, Macedo RM, Carvalho KAT, Faria Neto JR, Guarita-Souza LC; Critical revision of the manuscript for intellectual content: Winter SCN, Macedo RM, Francisco JC, Carvalho KAT, Faria Neto JR, Macedo ACB, Guarita-Souza LC. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This article is part of the thesis of master submitted by Simone de Campos Neitzke Winter, from Pontifícia Universidade Católica do Paraná. Ethics approval and consent to participate This study was approved by the Ethics Committee on Animal Experiments of the Colégio Brasileiro de Experimentação Animal (COBEA) under the protocol number 723/2012. 378