Self-selected or fixed: is there an optimal rest interval for controlling intensity in high-intensity interval resistance training?

PURPOSE: This study investigated the effects of different rest interval strategies during high-intensity interval resistance training (HIRT) on cardiorespiratory, perceptual, and enjoyment responses among trained young men. METHODS: Sixteen men experienced with HIRT underwent cardiopulmonary exercise testing and were familiarized with the exercises and HIRT protocol. On the subsequent three visits, interspaced 48-72 h, participants performed HIRT sessions with different rest intervals in a randomized order: 10 s and 30 s fixed rest intervals (FRI-10 and FRI-30), and self-selected rest interval (SSRI). Oxygen uptake (VO2), heart rate (HR), and recovery perception (Total Quality Recovery Scale) were measured during HIRT, while enjoyment responses (Physical Activity Enjoyment Scale) were assessed immediately after the sessions. RESULTS: The VO2 during exercise was greater in FRI-10 than FRI-30 (55% VO2max and 47% VO2max, respectively, p = 0.01), while no difference occurred between SSRI and bouts performed with fixed intervals (52% VO2max vs. FRI, p > 0.05). HR, excess post-exercise oxygen consumption (EPOC), recovery perception, and enjoyment responses were similar across conditions (p > 0.05). CONCLUSION: Exercise intensity was not affected by the rest interval strategy. High exercise intensity was maintained in sessions performed with FRI or SSRI, without negative repercussions on the duration of training sessions and enjoyment responses after exercise sessions.

Transcranial Direct Current Stimulation Combined With or Without Caffeine: Effects on Training Volume and Pain Perception.

Purpose: This study aimed to investigate the acute effects of tDCS combined with caffeine intake on training volume and pain perception in the bench press in resistance-trained males. The correlation between training volume and pain perception was also assessed in all interventions. Methods: Sixteen healthy males (age = 25.2 ± 4.7 years, body mass = 82.8 ± 9.1 kg, and height = 178.3 ± 5.7 cm), advanced in RT, were randomized and counterbalanced for the following experimental conditions: Sham tDCS with placebo intake (Sham+Pla), Sham tDCS with caffeine intake (Sham+Caff), anodal tDCS with placebo intake (a-tDCS+Pla), and anodal tDCS with caffeine intake (a-tDCS+Caff). The caffeine or placebo ingestion (both with 5 mg.kg-1) occurred 40 minutes before the tDCS sessions. The tDCS was applied over the left DLPFC for 20 minutes, with a 2 mA current intensity. After the tDCS sessions, participants performed the bench press with an 80% of 1RM load, where training volume and pain perception were measured. Results: Training volume was higher in the 1st and 2nd sets in both a-tDCS+Caff and Sham+Caff conditions, compared to the Sham+Pla condition (P < .05). Both a-tDCS+Caff and a-tDCS+Pla showed an increased pain perception during the third set compared to the first set. Also, no correlation was found between the number of repetitions and pain perception in any condition (P > .05). Conclusion: This research revealed that caffeine intake alone could be used as an ergogenic aid during resistance training programs in resistance-trained males.

Anodal Transcranial Direct Current Stimulation Does Not Affect Velocity Loss During a Typical Resistance Exercise Session.

Purpose: This study investigated the effects of transcranial direct current stimulation (tDCS) on velocity loss in a typical resistance exercise session. Methods: Twelve recreationally resistance-trained males (age = 24.8 ± 3.0 years, body mass = 78.9 ± 13.6 kg, and height = 174.3 ± 7.3 cm) completed two experimental trials in a counterbalanced crossover design: anodal tDCS and sham conditions. The stimuli were applied over the left dorsolateral prefrontal cortex for 20 minutes, using a 2 mA current intensity in anodal tDCS and a 1-minute active stimulus in the sham condition. After stimulation, subjects performed three sets of the bench press at a 70% of 1 maximum repetition intensity and 1 min of inter-set rest. The velocity loss was calculated as the relative difference between the fastest repetition velocity (usually first) and the velocity of the last repetition of each set and averaged over all three sets. Results: The results found no interaction between conditions and sets (P = .122), and no effect for conditions (P = .323) or sets (P = .364) for the velocity loss in each set. Also, no differences were found between the average velocity loss of the three sets in the anodal tDCS (-25.0 ± 4.7%) and sham condition (-23.3 ± 6.4%; P = .323). Conclusion: Anodal tDCS does not affect movement velocity in a typical strength training protocol in recreationally trained subjects.

Effects of cathodal transcranial direct current stimulation on hip range of motion of healthy sedentary women: A crossover study.

The improvements in range of motion (ROM) by cathodal transcranial direct current stimulation (c-tDCS) were only found in sedentary men and not in females. Thus, the study investigated the effect of c-tDCS on hip flexion range of motion (HFROM) in sedentary women. Ten healthy (27.2 ± 6.4 years for age, 67.9 ± 17.8 kg for body mass, 159.1 ± 7.1 cm for height, and 87.1 ± 3.3° for HFROM) and right-leg-dominant women performed a counterbalanced crossover design in two experimental sessions, separated a week apart: c-tDCS and placebo stimulus (sham). Before and after experimental conditions (Pre-stimulation, Post-stimulation), participants had their HFROM measured. A significant interaction was demonstrated for conditions × time (F(1, 9) = 10.666; ƞ2 = 0.542; p = 0.01), indicating an increase in HFROM in the post-condition (89.0 ± 2.6°) compared to pre-condition (86.5° ± 2.9°) only in the c-tDCS. However, the HFROM improvements varied from 0.3 % to 6.5 % following c-tDCS. This study suggests that c-tDCS applied over the sensorimotor cortex of healthy sedentary women can acutely improve HFROM, but with a low percentage increase.

Effects of Anodal Transcranial Direct Current Stimulation on Training Volume and Pleasure Responses in the Back Squat Exercise Following a Bench Press.

ABSTRACT: Rodrigues, GM, Machado, S, Faria Vieira, LA, Ramalho de Oliveira, BR, Jesus Abreu, MA, Marquez, G, Maranhão Neto, GA, and Lattari, E. Effects of anodal transcranial direct current stimulation on training volume and pleasure responses in the back squat exercise following a bench press. J Strength Cond Res 36(11): 3048-3055, 2022-This study aimed to investigate the effects of anodal transcranial direct current stimulation (a-tDCS) on volume-load and pleasure responses in a back squat following a bench press. Twelve male subjects advanced in resistance training (RT) (age, 25.5 ± 4.4 years) completed 2 experimental trials in a counterbalanced crossover design: a-tDCS and sham conditions. The stimulus was applied over the left dorsolateral prefrontal cortex for 20 minutes using a 2-mA current intensity in a-tDCS condition and 1 minute of active stimulus in the sham condition. Immediately after stimulation, subjects performed the bench press followed by the back squat. The exercise protocol consisted of 3 sets of maximum repetitions at an intensity of 80% of 1 repetition maximum. The volume-load, perceived pleasure, and arousal responses were measured during the RT protocol. The results indicated that volume-load was higher in the a-tDCS condition than in the sham condition for both exercises ( p = 0.02), with large effect for the back squat ( p = 0.045; d = 0.96). The higher volume-load was obtained by increasing the number of repetitions across all sets for the bench press ( p ≤ 0.0001) and only in the first set for the back squat ( p = 0.01). The circumplex model analysis showed a higher pleasure in the bench press and a tendency toward a higher pleasure in the a-tDCS condition. Anodal tDCS may be used as an ergogenic resource for increasing the back squat volume after performing the bench press in resistance-trained male subjects.

Transcranial Direct Current Stimulation (tDCS) Improves Back-Squat Performance in Intermediate Resistance-Training Men.

Purpose: The purpose of this study was to evaluate the effects of anodal tDCS applied over the dorsolateral prefrontal cortex (DLPFC) on muscle endurance in the back-squat exercise. Methods: Eleven healthy males, intermediate in resistance training (RT), aged between 18 and 31 years (25.5 ± 4.4 years) were recruited. In the initial visits (1st and 2nd visits), participants performed a 1RM test to determine the load in the back-squat exercise. Following the two initials visits, participants attended the lab for the two experimental conditions (anodal tDCS and sham), which were completed a week apart, with sessions randomly counterbalanced. The stimulation was applied over the DLPFC for 20 minutes using a 2 mA current intensity. Immediately after the experimental conditions, participants completed three sets of maximum repetitions (80% of 1RM), with a 1-minute recovery interval between each set in the back-squat exercise. Muscle endurance was determined by the total number of repetitions and the number of repetitions in each set. Results: The total number of repetitions was higher in the anodal tDCS condition compared to sham condition (p ≤ .0001). Moreover, the number of repetitions performed in the first set was higher for anodal tDCS condition than in the sham condition (p ≤ .01). Conclusion: This study found improvement in back-squat exercise performance after the application of anodal tDCS. The effects of anodal tDCS applied over DLPFC may be a promising ergogenic resource on muscle endurance in the back-squat exercise.

Correlation between economy/efficiency and mountain biking cross-country race performance.

This study investigated the correlation between cycling economy (CE) and gross efficiency (GE) in Olympic cross-country mountain biking (XCO-MTB) race performance. Also was examined the correlation between CE, GE, and peak oxygen uptake (VO2peak). Sixteen male XCO-MTB athletes (30.9 ± 5.2 years, 68.7 ± 5.6 kg, 175.0 ± 5.7 cm, and VO2peak: 65.4 ± 4.9 mL·kg-1 min-1) completed two experimental sessions. On the first, anthropometric assessments and a maximal incremental test were performed. The maximal incremental test was performed in the cycle ergometer to determine VO2peak, CE, and GE. A week later, an XCO-MTB race was performed in the second visit, where the official race time was used as a performance indicator. An inverse, significant moderate correlation was found between race time (8318.3 ± 459.0 s) and both CE (r = -0.53; CI95% = -0.84 to -0.10; p = 0.0008), and GE (r = -0.67; CI95% = -0.89 to -0.22; p = 0.0001). However, the moderate correlation between CE and race time showed low power. No significant correlation was found between VO2peak and either CE (r = -0.45; CI95% = -0.77-0.06; p = 0.08) or GE (r = -0.47; CI95% = -0.78-0.04; p = 0.07). In conclusion, gross efficiency is an important component of XCO-MTB race performance. The VO2peak was not related to CE and GE. The evaluation of GE may be a useful addition to the battery of physiological tests in mountain bikers.Highlights The gross efficiency can be a performance indicator related to the Olympic cross-country mountain biking race;The cycling economy has a moderate association with race time, but its use as a measure related to Olympic cross-country mountain biking race performance should be carried out with caution;Despite VO2peak's influence on both cycling economy and gross efficiency measures, our results do not show a relationship with Olympic cross-country mountain biking athletes.

Anodal Transcranial Direct Current Stimulation Increases Muscular Strength and Reduces Pain Perception in Women With Patellofemoral Pain.

ABSTRACT: Rodrigues, GM, Paixão, A, Arruda, T, de Oliveira, BRR, Maranhão Neto, GA, Marques Neto, SR, Lattari, E, and Machado, S. Anodal transcranial direct current stimulation increases muscular strength and reduces pain perception in women with patellofemoral pain. J Strength Cond Res 36(2): 371-378, 2022-The purpose of this study is to investigate the effects of anodic transcranial direct current stimulation applied to motor cortex combined with open kinetic chain exercises on muscular strength and pain perception in women with patellofemoral pain (PFP). Twenty-eight women aged between 18 and 30 years with PFP were selected. Subjects were randomized in 2 groups, anodic stimulus plus resistance training (n = 14; anodic transcranial direct current stimulation [a-tDCS] + RT) or placebo stimulus plus resistance training (n = 14; Sham + RT) and attended the laboratory for 12 experimental sessions, 48-72 hours apart from each other. The RT protocol consisted of 3 sets of 12 repetitions of the knee extension exercise at 60% of 10 maximal repetition (10RM) with a 1-minute interval between sets. In the a-tDCS + RT group, a 2-mA current was applied for 20 minutes over the motor cortex before the RT protocol in each session. In the Sham + RT group, the stimulus was interrupted after 30 seconds. Preintervention, fourth session, eighth session, and postintervention, load was assessed through a 10RM test. The pain perception was assessed through Clarke sign maneuver (CSM) and measured through a visual analogue scale for pain. The a-tDCS + RT group showed greater 10RM load than Sham + RT group at eighth session (p < 0.05) and postintervention (p < 0.05). In a-tDCS + RT group, pain perception reduced in the postintervention compared with preintervention (p < 0.05). The intervention a-tDCS + RT was able to improve muscular strength in women with PFP. In addition, pain perception only decreased postintervention in the a-tDCS + RT group. This combined intervention can be used by coaches in rehabilitation programs aiming to treat PFP through medium-term strength gains.

Can transcranial direct current stimulation improve range of motion and modulate pain perception in healthy individuals?

The objective of the present study was to investigate the effects of different electrode assemblies and electric current polarity on the ROM of the hip and pain perception. Ten healthy male, sedentary, right-leg-dominant, and aged between 19 and 30 years (24.0 ± 4.0 years) subjects were recruited. For the experimental conditions, the application of transcranial direct current stimulation (tDCS) was performed with the following montages. In the montage 1, the cathodal electrode was placed over the motor cortex (MC) horizontally, and the anodal electrode was positioned over the left dorsolateral prefrontal cortex (DLPFC). In the montage 2, the anodal electrode was placed over the MC bilaterally, and the cathode electrode was positioned over the left DLPFC. The sham montage was the same as the montage 1. In the montage 1 and 2 stimulation was applied with 2 mA current intensity for 20 min. In the Sham condition, the stimulator was turned off after 30 s of active stimulation and the electrodes remained on the participants for 20 min. Before and after experimental conditions (Pre-stimulation, Post-stimulation), the maximum Hip ROM and pain perception was measured. For the Montage 1, the maximum Hip ROM increased in post-stimulation compared to pre-stimulation, and in the Montage 2, the maximum Hip ROM decreased in post-stimulation compared to pre-stimulation. The pain perception in the Montage 1 decreased in the post-stimulation compared to pre-stimulation. In the post-stimulation, pain perception for the Montage 1 was lower compared to Montage 2 (p = 0.005), and sham (p = 0.004). When the anodic stimulus was applied on the left DLPFC and the cathodic stimulus on the motor cortex, an increase in ROM and a reduction in the pain perception was observed. This montage may to modulate pain perception and joint flexibility.