Resistance Training to Muscle Failure with Variable Load Intensities: Implications for Post-Exercise Blood Pressure and Heart Rate Variability in Trained Men

Abstract

Background: The modulation of cardiac sympathovagal balance alters following acute resistance training (RT) sessions. Nevertheless, the precise influence of RT at varying load intensities on this physiological response remains to be fully elucidated. Therefore, the aim of this study was to compare the time course of recovery following low- (40%), moderate- (60%), and high- (80%) load-intensity RT protocols performed up to muscle repetition failure in resistance-trained men. Method: Sixteen young, resistance-trained men (mean age: 21.6 ± 2.5 years, mean height: 175.7 ± 8.9 cm, mean weight: 77.1 ± 11.3 kg) participated in a randomized crossover experimental design involving three sessions, each taken to the point of muscle failure. These sessions were characterized by different load intensities: low (40% of 1-repetition maximum, 1RM), moderate (60% of 1RM), and high (80% of 1RM). The exercise regimen comprised four exercises-back squat (BS), bench press (BnP), barbell row (BR), and shoulder press (SP)-with each exercise consisting of three sets. Throughout each session, heart rate variability (HRV) and blood pressure (BP) parameters were assessed both pre-exercise and during a 40 min post-exercise period, segmented into 10 min intervals for stabilization. Statistical analysis involved the use of a repeated measures ANOVA. Results: It was observed that the 40% and 60% RT sessions resulted in a significantly higher root mean square of successive R-R intervals (RMSSD) value compared to the 80% RT session in the post-exercise recovery process in 30 min (respectively, p = 0.025; p = 0.028) and 40 min (respectively, p = 0.031; p = 0.046), while the 40% and 60% RT sessions produced similar responses. The 40% RT session was significantly higher in the high frequency (HF) value post-exercise in 40 min compared to the 80% RT session (p = 0.045). Conclusions: Our findings suggest that engaging in resistance training (RT) sessions to muscle failure at an intensity of 80% induces acute increases in sympathetic activity, potentially leading to elevated cardiovascular stress. For individuals with normal blood pressure, it is advisable to opt for lighter loads and higher repetition volumes when prescribing RT, as heavier-load RT may carry an increased risk of cardiac-related factors.

Keywords: cardiac autonomic modulation; recovery; resistance exercise; sympathovagal balance; tension.

Figure 1

Resistance training. (A1,A2) Back squat, (B1,B2) bench press, (C1,C2) barbell row, and (D1,D2) shoulder press.

Figure 2

Shows the values of SBP and DBP. SBP, systolic blood pressure; DBP, diastolic blood pressure. * There is a significant difference in the 40% exercise method compared to pre-exercise p < 0.05. # There is a significant difference in the 60% exercise method compared to pre-exercise p < 0.05.

Figure 3

Shows the time and group interactions of the RMSSD. RMSSD, root mean of the square of the difference in the RR intervals. * There is a significant difference in the 40% exercise method compared to pre-exercise p < 0.05. # There is a significant difference in the 60% exercise method compared to pre-exercise p < 0.05. ¥ There is a significant difference in the 80% exercise method compared to pre-exercise p < 0.05. α There are significant differences between the 40% and 80% exercise method in 30 min and 40 min.

Figure 4

Shows the time and group interactions of HF and LF. HF, high frequency; LF, low frequency. * There is a significant difference in the 40% exercise method compared to pre-exercise p < 0.05. # There is a significant difference in the 60% exercise method compared to pre-exercise p < 0.05. ¥ There is a significant difference in the 80% exercise method compared to pre-exercise p < 0.05. α There are significant differences between the 40% and 80% exercise method in 40 min.