Parasympathetic Nervous Activity Responses to Different Resistance Training Systems

Combined Accentuated Eccentric Loading and Rest Redistribution in High-Volume Back Squat: Acute Stimulus and Fatigue

ABSTRACT

Chae, S, Long, SA, Lis, RP, McDowell, KW, Wagle, JP, Carroll, KM, Mizuguchi, S, and Stone, MH. Combined accentuated eccentric loading and rest redistribution in high-volume back squat: Acute stimulus and fatigue. J Strength Cond Res 38(4): 648-655, 2024-The purpose of this study was to examine acute stimulus and fatigue responses to combined accentuated eccentric loading and rest redistribution (AEL + RR). Resistance-trained men ( n = 12, 25.6 ± 4.4 years, 1.77 ± 0.06 m, and 81.7 ± 11.4 kg) completed a back squat (BS) 1 repetition maximum (1RM) and weight releaser familiarization session. Three BS exercise conditions (sets × repetitions × eccentric-concentric loading) consisted of (a) 3 × (5 × 2) × 110/60% (AEL + RR 5), (b) 3 × (2 × 5) × 110/60% (AEL + RR 2), and (c) 3 × 10 × 60/60% 1RM (traditional sets [TS]). Weight releasers (50% 1RM) were attached to every first repetition of each cluster set (every first, third, fifth, seventh, and ninth repetition in AEL + RR 5 and every first and sixth repetition in AEL + RR 2). The AEL + RR 5 resulted in greater total volume load (sets × repetitions × eccentric + concentric loading) (6,630 ± 1,210 kg) when compared with AEL + RR 2 (5,944 ± 1,085 kg) and TS (5,487 ± 1,002 kg). In addition, AEL + RR 5 led to significantly ( p < 0.05) greater rating of perceived exertion (RPE) after set 2 and set 3 and lower blood lactate (BL) after set 3 and 5, 15, and 25 minutes postexercise than AEL + RR 2 and TS. There was a main effect of condition for BL between AEL + RR 5 (5.11 ± 2.90 mmol·L -1 ), AEL + RR 2 (6.23 ± 3.22 mmol·L -1 ), and TS (6.15 ± 3.17 mmol·L -1 ). In summary, AEL + RR 5 results in unique stimulus and fatigue responses. Although it may increase perceived exertion, coaches could use AEL + RR 5 to achieve greater back squat total volume load while reducing BL accumulation.

Effects of smartphone use before resistance exercise on inhibitory control, heart rate variability, and countermovement jump

BACKGROUND

The effect of MF induced by exposure time to social media smartphone apps on inhibitory control, heart rate variability (HRV), and high-intensity physical effort following a resistance exercise session might indicate whether strength and conditioning professionals should suggest avoiding smartphone usage before a resistance exercise session.

AIM

The objective of this study was to analyze the effect of mental fatigue on inhibitory control, HRV, and countermovement jump (CMJ) in trained adults after resistance exercise.

METHODS

A total of 16 trained males (21.4 ± 3.3 years) volunteered in this study. The participants performed resistance exercises with and without mental fatigue. The Stroop Task, countermovement jump, and heart rate variability were evaluated before and after the resistance exercise. The participants used smartphones in the mental fatigue condition, whereas the participants watched TV in the control condition.

RESULTS

No condition × time interaction was found for the Stroop accuracy (p = 0.87), CMJ (p = 0.68), SDNN (p = 0.15), or pNN50 (p = 0.15) in the heart rate variability. An interaction was found for Stroop response time (p = 0.01) with a higher response time for the mental fatigue condition (p = 0.01).

CONCLUSIONS

Mental fatigue impaired the inhibitory control performance after a resistance exercise session in trained adults.

Effect of resistance training on heart rate variability of anxious female college students

Introduction

Female college students are a group with high incidence of anxiety, and anxiety will lead to the disorder of autonomic nervous system (ANS), which will adversely affect their study and life. Resistance training plays a positive role in improving anxiety, but there is little evidence on whether resistance training can improve ANS of anxious female college students. Heart rate variability (HRV) has gained widespread acceptance in assessing ANS modulation. Therefore, the objective of this study aimed to investigate the effects of resistance training on heart rate variability (HRV) in anxious female college student.

Methods

A randomized controlled study of resistance training intervention was conducted in 27 anxious female college students that assigned randomly into an intervention group (n = 14) and a control group (n = 13). The intervention group was intervened by cluster training for 8 weeks. Self-rating anxiety scale (SAS) was used. ANS is evaluated by short-term HRV. Muscle strength was assessed by 1 RM indirect method. Independent-sample t-test was used to test post-test-pre-test scores between the intervention and control groups.

Results

After the intervention, SAS score of the intervention group was significantly decreased (P < 0.05), SDNN of the intervention group was significantly increased (P < 0.05) and LF/HF was significantly decreased (P < 0.05).

Conclusion

The resistance training intervention adopted in this study significantly increased the HRV of anxious female college students and improved their autonomic nervous disorder.

Acute Physiological and Perceptual Responses to Rest Redistribution With Heavier Loads in Resistance-Trained Men

ABSTRACT

Chae, S, Hill, DW, Bailey, CA, Moses, SA, McMullen, SM, and Vingren, JL. Acute physiological and perceptual responses to rest redistribution with heavier loads in resistance-trained men. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this study was to explore the effect of rest redistribution with heavier loads (RR + L) on physiological and perceptual responses in resistance-trained men. Eight men who had back squat (BS) 1 repetition maximum (1RM) to body mass ratio; 1.8 ± 0.2 completed 2 BS exercise sessions in a counterbalanced and a randomized order; RR + L: 4 sets of (2 × 5) repetitions with 90-second interset rest and 30-second intraset rest using 75% BS 1RM and traditional sets (TS): 4 sets of 10 repetitions with 120-second interset rest using 70% BS 1RM. Blood samples were collected before exercise, immediately post exercise, and 5, 15, and 30 minutes post exercise for the analysis of growth hormone (GH), total testosterone (TT), cortisol (C), and blood lactate (BL), whereas rating of perceived exertion (RPE) and heart rate (HR) were measured immediately after each set of the BS exercise. While neither main effect of condition nor interaction existed, there was a significant (p < 0.05) main effect of time point (and set) for GH, TT, C, BL, RPE, and HR. Volume load was greater for RR + L compared with TS (4,074.9 ± 786.7 kg vs. 3,796.3 ± 714.8 kg). In conclusion, RR + L increases volume load by approximately 7% but does not seem to influence GH (g = -0.15), TT (g = -0.09), BL (g = -0.22), RPE (g = 0.14), and HR (g = -0.08) responses. Practitioners may consider using RR + L to increase volume load without increasing acute fatigue responses.

Hemodynamic response to different set configurations of a moderate-load resistance exercise

We aimed to determine the cardiovascular responses to two different set configuration resistance-exercise protocols during a knee extension composed of 40 repetitions with a 15RM load and a total resting time of 360 seconds. Twenty-four healthy sport science students randomly performed two sessions: (a) a long set configuration session (LSC: 4 sets of 10 repetitions with 2 min rest between sets) and (b) a short set configuration session (SSC: 8 sets of 5 repetitions with 51 s rest between sets). Before and during exercise, peak and mean values of heart rate, blood pressure, rate pressure product, and pulse pressure were obtained. Results showed that both protocols increased the overall peak and mean blood pressure values (p < 0.001). However, LSC entailed a higher peak blood pressure response at the last set (p = 0.041) and an increase throughout the first 30 repetitions (p ≤ 0.007), while SSC kept steady after the first 20 repetitions. Additionally, LSC caused higher overall peak and mean heart rate and rate pressure product values (p ≤ 0.003). Summarily, although both protocols raised blood pressure, SSC reduced the extent of the pressure and chronotropic response during resistance exercise.

Changes in Heart Rate Variability and Post‐Exercise Blood Pressure from Manipulating Rest Intervals Between Sets of Resistance Training

The purpose of this study was to compare blood pressure and heart rate variability responses in physically active men after performing resistance training sessions with rest intervals of 1 min, 2 min and 3 min. Eighteen men (age, 21.6±1.1 years; body mass, 74.1±8.1 kg; body height, 175.3±7.1 cm) who performed 180min of physical activity per week participated in this study. After determining the 15RM loads for the squat, bench press, bent-over row and deadlift, participants performed a resistance training session. Participants performed three resistance training protocols in randomized counterbalanced order. Each experimental protocol comprised different rest intervals between sets of resistance training exercises (1min, 2min or 3min). During each experimental session, participants performed three sets with a 15RM load. Blood pressure and heart rate variability were measured before and for 2h after each session. The results demonstrated a greater blood pressure (p<0.05) reduction with a longer rest interval. There was no statistically significant difference in heart rate variability changes between groups. These results indicate that 2min and 3min rest intervals while using a 15RM load provide the best stimulus for a blood pressure reduction response after a resistance training session. Our findings suggest that strength and conditioning professionals should prescribe 2min or 3min rest intervals when resistance training is performed with a 15RM load if the aim is to obtain an acute reduction in blood pressure after a resistance training session.

Acute Effects of Parallel Back Squat Performed in Different Set Configurations on Neuromuscular Performance

We compared the acute effects of parallel back squat performed from different resistance training configurations on neuromuscular performance. Twenty-eight young adults underwent 4 experimental conditions: inter-repetition rest, traditional, traditional to failure, and rest-pause in the parallel back squat in a randomized, counterbalanced, and cross-over design. The neuromuscular performance was assessed through peak torque of knee extensors and flexors at two angular velocities (90 and 120 º/s) in three moments (before, post, and post-30 min). The peak torque of the knee extensors and flexors at 90 and 120 º/s decreased immediately after training for traditional, traditional to failure, and rest-pause (-8.1% to -17.7%, P<0.001). A greater reduction in the extensor peak torque was found at 120 º/s (P<0.05) in the rest-pause (-17.7%) when compared to traditional (-10.8%). The peak torque returned to baseline values only at post-30 min for the traditional configuration for the knee flexion action at 120 º/s. The peak torque remained similar for the muscular actions and angular velocities for the inter-repetition rest (P>0.05). Our results suggest the inter-repetition rest configuration seems to be a more appropriate strategy for maintaining the lower limb neuromuscular performance after a resistance training session.

Mental Fatigue From Smartphone Use Reduces Volume-Load in Resistance Training: A Randomized, Single-Blinded Cross-Over Study

We investigated the acute effects of mental fatigue induced by 30-minute use of smartphone social network apps on volume load in resistance training among recreationally trained adults. Sixteen (n = 16) adults of both sexes performed three sets of a half back-squat exercise to failure with 80% of 15RM, interspersed with 3-minutes of passive recovery between sets, before and after two different cognitive tasks: (a) use of smartphone social network apps; and (b) watching a documentary. We assessed mechanical variables and ratings of perceived exertion during the strength exercise. Relative to the documentary-viewing control condition, a 30-minute exposure to smartphone social network apps led participants toward increased perception of mental fatigue (p = 0.004) and lower volume-load during the strength exercise (p = 0.006). There were no significant differences in perceived exertion between conditions (p = 0.54), participants' motivation (p = 0.277), intra-set mechanical variables (p > 0.05), or blood lactate concentrations (p = 0.36). Our findings of an isolated possible higher-than normal RPE without changes in physiological variables, accompanying the lower volume-load in the mentally-fatigued participants support psychological, rather than physiological, bases for mental fatigue effects.