Variabilidade da frequência cardíaca em ratos submetidos a suplementação de creatina e ao treinamento de força

Abstract

Introduction: Heart rate variability is frequently associated with physical exercise, which seems to produce any changes in both absolute heart rate and variability. Objective: To evaluate the autonomic cardiac control follow-on from creatine supplementation in sedentary animals and strength training group. Material and methods: Wistar rats were divided into three groups: Control Group (Control), creatine group (CRE) and training + creatine (TRN+CRE). The CRE+TRN group underwent vertical climbing, with overload apparatus attached to the proximal portion of the tail with adhesive tape. The protocol consisted in carrying out 50%, 75%, 90% and 100% increases of the maximum load established in the previous session, with subsequent loads being given every 30g. The rest time consisted of 2 minutes. Results: In relation to body weight, the groups presented values of (Control: 318 ± 9,5 grams vs CRE: 368 ± 14 grams vs TRN+CRE 419±12 grams). Regarding the performance at 8 weeks, all values from week 2 presented statistical difference in relation to week 1, but the last three weeks did not show any differences between them. When the visceral fat was analyzed, the CRE group presented higher levels compared to the Control group and the TRN+CRE group (Control: 3,2 ± 0,4 grams vs CRE: 5,04 ± 0,59 grams vs TRN+CRE 3,29 ± 0,19 grams). The baseline of HR showed no differences between the three groups (Control: 359 ± 12 bpm; CRE: 349 ± 16 bpm; TRN+CRE: 353 ± 17 bpm), similar results were presented for Intervals RR (Control: 168 ± 17 ms; CRE: 172 ± 3,24 bpm; TRN+CRE: 171 ± 3,41 ms). In relation to the SDNN, and rMSSD indices, there was a reduction of the same in the CRE group compared to the other two groups, with values of (Control: 6,39±1,10 ms; CRE: 3,47±0,98 ms; TRN±CRE: 6,32±1,06) e (Control: 3,37±0,17 ms; CRE: 2,19±0,25 ms; TRN+CRE: 3,38±0,48 ms). When analyzed the HRV in domain time, a greater sympathetic modulation was observed, represented by the Low frequency component (LF-nu,%) for the CRE and TRN+CRE groups (CRE: 39,13 ± 2,47, ms²; TRN+CRE: 34,50 ± 3,82, ms²) in relation to the Control group (Control: 22,84 ± 2,56, ms²). In relation to the high frequency component (HFnu,%), the CRE and TRN+CRE groups had their values reduced in relation to the Control group (CRE: 52,08 ± 3,13 %; TRN+CRE 54,60 ± 3,08 % vs Control: 67,50 ± 5,71, %). Finally, when analyzing the autonomic balance, represented by the LF/HF ratio, it was observed the CRE and TRN+CRE groups has a higher index when compared to the Control groups (CRE: 0,75 ± 0,08; TRN+CRE: 0,71 ± 10 vs Control: 0,37 ± 0,06; p<0.05). Conclusion: It is concluded that the supplementation with creatine may have beneficial effects when associated with physical training, but its supplementation alone can increase visceral fat levels, reduce heart rate variability, and this is a important predictive factor to increased risk of cardiovascular diseases.

Key Words: Creatine, Heart Rate, Heart Rate Variability, Resistance Training.