Efeito agudo de dois protocolos isométricos equalizados na relação esforço: pausa (work-to-rest ratio): respostas hemodinâmicas e autonômicas

Abstract

Introduction: Little is known about the effects of distinct, equalized in work-to-rest (W:R) ratio set configuration on hemodynamic and autonomic response during and after acute strength training session. Objective: To analyze the acute effects of two isometric, equalized in W:R ratio set configurations protocols on hemodynamic and autonomic responses in normotensive women. Materials and Methods: 11 normotensive females (25 ± 3 years, height: 1.63 ± 0.07 meters, body mass: 60.7 ± 6.0 kg, body mass index (BMI): 22.7 ± 1.3 kg/m2, systolic blood pressure (SBP): 112 ± 10 mmHg, diastolic blood pressure (DBP): 71 ± 5 mmHg, heart rate (HR): 73 ± 11 bpm, one repetition maximum (1RM): 249 ± 62kg) performed two isometric protocols equalized in W:R on different days and random order. Protocol A: 4 sets x 2 min isometric x 2 min intervals. Protocol B: 16 sets x 30 sec isometric x 24 sec interval between sets. The standardized load was 30% 1-RM (75 ± 19kg) for both protocols. The protocols had the same total time under tension (480s), total rest (360s), and total sustained weight (30% 1-RM). Hemodynamic and autonomic variables were continuously monitored by photoplestimography. During the protocols, the perceived exertion scale for resistance exercise and rate pressure product were collected. Results: During protocols there was a significant increase in SBP, DBP and mean blood pressure (MAP) along the sets/blocks in both protocols with a significant difference from rest (p <0.05). There was no difference between the protocols for SBP and MAP (p> 0.05). For DBP, only set/block 1 presented difference between protocols (p <0.05). There were significant increases in heart rate (HR), cardiac output (Qc) and rate pressure product (RPP) over all sets/blocks for both protocols (p <0.05). Protocol A (4:2m:2m) induced higher HR throughout the entire protocol compared to B (16:30s:24s) (p<0.05). There was also a significant difference between protocols in the last sets/blocks (2, 3 and 4), with higher values in Protocol A (p = 0.026930; p = 0.026904; p = 0.008819, respectively). For RPP, the only difference was observed inset/block 4 (p = 0.032397). There was no post-exercise hypotension (SBP, DBP and MAP) after both protocols (p> 0.05) within 60 minutes. The protocol A induced lower post-exercise BP values up to 20 minutes after session compared to protocol B (p <0.05). HR remained elevated up to 60 minutes after protocol A when compared to rest (p <0.05). The protocol B induced lower values in HR and Qc up to 20 minutes after session compared to protocol A (p <0.05). There was no statistical difference in stroke volume (SV) values during and after the protocols. Regarding the ANS, there was no cardiovagal recovery up to 60 minutes after session, for both time and frequency domains. For time domain, it was possible to observe a significant reduction in RMSSD for protocol A compared to rest, showing difference between protocols, with greater reductions in protocol A up to 20 minutes. Conclusions: Short time under tension protocol, configuration in cluster (16:30s:24s), induced lower autonomic stress and cardiovascular overload than longer time under tension protocol (4:2m:2m), especially for HR and cardiac output.