Abstract

Objective: The objective of the study was to verify the autonomic response by analyzing heart rate variability in the frequency domain, after strength training with supplementation of citrus aurantium.

Method: Participated in the present study, 10 men (28.2±3.8 years; 1.760.03m; 79.33.9kg; 25.52.1 BMI) trained with previous experience in strength training activity of at least six months. Heart rate variability (HRV) was measured in a 5-minute window over 10 minutes with the individual in a sitting position, before, in two pre-exercise moments (before and 30 minutes after supplementation), immediately after exercise for 60 minutes. Frequency domain indices were used for HRV analysis, being: The components of low frequency (LF - sympathetic activation indicator), high frequency (HF - parasympathetic activation indicator) and the ratio between low and high frequency (LF/HF - sympathetic vagal balance indicator). Participants supplemented 975mg of citrus aurantium dry extract (6% synephrine) (S) or maltodextrin (P) placebo. They performed five sets with loads of 70% 1-RM, in the horizontal bench press exercise (SH) with supplementation with citrus aurantium or with the intake of placebo. The Shapiro-Wilk normality test was used and a repeated-measures ANOVA was conducted to analyze all samples, cardiovascular, followed by a Fisher post hoc, when necessary. All analyzes were performed using SPSS version 21.0 (IBM, I.C.). The significance value adopted was p≤0.05 in all tests.

Results: For LF, there were no significant differences between the supplementation conditions (p=0.063), as well as the different supplementation conditions, where no significant changes were observed (p=0.177) and for the different moments of checks (p=0.085). In the HF, there were significant differences between the interactions (p=0.043), however, for the two conditions, supplementation (p=0.317) and different verification moments (p= 0.178), no significant differences were verified. In LF/HF there were significant differences in the interaction (p =0.011) and between the different supplementation conditions, there were no significant changes (p=0.626). Between the moments of verification, differences were also observed (p=0.032).

Conclusion: The present study did not find significant differences in heart rate variability with different types of supplementation. However, supplementation with citrus aurantium was able to stimulate the autonomic sympathetic response even at the pre-exercise moment, signaling that p-synephrine may present some changes in the cardiovascular system. Thus, it is worth paying attention to the prescriptions of this supplement.

Keywords

heart rate variability, strength training, citrus aurantium, ergogenic resources, cardiovascular effects, physical activities, musculoskeletal conditions, endocrine diseases, heart disease