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JEPonline

Acute Effectsof Fixed Rest Timeduring Multiple Setson Upper Limbs Performance

Bruno Rodrigues1,Alex Souto Maior2 , Raphael Sakugawa3, Mateus Rossato1,3, Ewertton Bezerra1,3

1Human Performance Laboratory – Federal University of Amazonas, AM, Brazil; 2Augusto Motta University (UNISUAM), Postgraduate Program in Rehabilitation Sciences; 3Biomechanics Laboratory – Federal University of Santa Catarina, SC, Brazil

ABSTRACT

Rodrigues B, Maior AS, Sakugawa R, Bezerra E. Acute Effects of Fixed Rest Time during Multiple Sets on Upper Limbs Performance.JEPonline2018;21(3):86-93. This study analyzedthe acute effects ofa 2-min rest interval on range of motion (ROM), blood lactate, and myoelectric activation (sEMG). Ten healthy resistance-trained menparticipated in the experimental protocol. Previously, they performed test and retest of 10RM (repetition maximum) on bench press (BP). After 48hrs, the myoelectric activation on upper trunk and arm muscles; ROM elbow flexion; and blood lactate level were monitored before, during, and after 3 sets of BP with a 2-minrest interval between sets. Triceps brachiisEMG showed a decrease in set 2 and set 3 when compared toset 1 (P<0.05). Rectus abdominissEMGincreased in set 3 when compared to sets 1 and 2(P<0.05). There were no significant differences on myoelectric activity for thepectoralis major andanterior deltoidbetween sets (P>0.05) and phases (P>0.05), respectively.Elbow flexionshoweda higher ROM during set 1when compared to sets 2and 3 (P<0.05). Elbow extension showed no significant difference between sets(P>0.05). Blood lactate showed increase over the periods (set 3>set2>set 1rest, P<0.05). Absolute load volume was lower in set 3 in relation to set 2 and set 1 (P<0.05). We conclude thatthe fixed interval of 2 min is not sufficient to control for reduction in performance during bench press with load of 10RM. Thus, we suggest a rest time 2 min for better performance in this specific exercise for multiple sets.

Key Words:Electromyography, Kinematic, Resistance Training

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INTRODUCTION

Although resistance training (RT) is associated with an improvement in muscular strength, power, hypertrophy, and localized muscular endurance(15), there are several variables that must be taken into consideration. Among them are weekly frequency, external load, training volume, number of exercises, movement pace, exercise order, and rest interval between sets (9). With regard to the rest interval (RI), it is easy to manipulateto influence the intensity during a RT session.Thus,the RI is a resistance-related variable that can have a direct affect on the performance of subsequent sets. For example, an incorrect RI can result in a decrease in efficiency and ultimately the effectiveness of a RT program (18). Conversely, when the RI is appropriate for the individual, it can produce positive acute responses and chronic adaptations in the neuromuscular and endocrine systems (4).

Recently, Grgic et al. (9) reported that longer intervals (i.e., ≥60 sec) may be more beneficial for developing muscle hypertrophy. On the other hand, the ACSM (2) position stand recommends that RI should be based on muscle recruitment (e.g., multi-joint use 2 to 3 min between sets whilesingle-joint exercise should use 1 to 2 min between sets). But, it is important to point out that the recommendations were based on a study byAbdessemedand colleagues (1). They reported on the effects of three different rest intervals of 1, 3, and 5 min between sets on power output during the bench press exercise.

Monteiro et al. (13) investigated the influence of different exercise-recovery-ratio (ERR) and fixed RI on the training volume in sessions designed to produce hypertrophy with upper-body exercises recruiting different muscle mass.They concluded that between-set RI based on ERR instead of using fixed intervals did not enable more work to be done in multiple-set/high intensity resistance training sessions. In short, the fixed rest intervals (2 min) and self-suggested time intervals during bench press exercise are equivalent in terms of recovery for the forthcoming set (8).Despite the focus of these studies on the RI between sets as mentioned above, there remains a lack of evidence regarding the influence of the RI between sets on volume load, and upper body myoelectric activity, range of motion, and blood lactate after multiple sets.

Therefore, the purpose of this study was to investigate the influence of a fixed rest interval of 2 min on volume load, upper body myoelectric activity, range of motion, and blood lactate after multiple sets during thebench press exercise.

METHODS

Subjects

Ten healthy resistance-trained men participated in this study (age, 27 ± 5 yrs;weight, 77 ± 9kg;height, 1.71 ± 0.06m). They had at least 1 yr of recreational RT experience with performing routine exercises at least 4 to 5 hrs·wk-1).All subjects completed the Physical ActivityReadiness Questionnaire (PAR-Q).They reportedno shoulder injury or pathology at the moment of the experiment or during the previous 6 months. The University Ethics Committee approved the project. The subjects read and signed an informed consent form, as required by Resolution 466/2012 of the Brazil National Health Council for research on human subjects.Body mass was measured to the nearest 0.1 kg using a calibrated physician’s beam scale (Model 31, Filizola, Sao Paulo, Brazil), while the subjects were dressed in shorts. Height was determined without shoes to the nearest 0.1 cm using a stadiometer scale (Model 31, FilizolaR). Body fat percentage (%) was estimated using the 7-site skinfold method.

Procedures

An exploratory design was used to analyze the effect of fixed rest intervals on volume load, and upper body myoelectric activity, range of motion, and blood lactateduring 3 sets while doing the BP exercise.Previously, test and retest 10RM load for BP was determined foreachsubject,which was separated by least 48 hrs between the sessions.The BP exercise was performed onLife Fitness equipment (Life Fitness, Rosemont, IL, USA). During the 10RM testing, the subjects were given a maximum of 3attempts with a 5-min rest between attempts(6). A metronome controlled for an exercise executioncadenceof 2 sec for the ascent phase and 2 sec for the descent phase)(3).A biacromial distance was adopted to standardize the grip width. The 10RM test result was 81.6 kg, with Interclass correlation coefficient of 0.96. Absolute load volume was calculated for each set (repetition for set x 10RM load). During the experimental protocol, the subjects performed 3 sets with 2 min between the sets.

Plasma blood lactate monitoring was carried out a by portable analyzer (ACCUSPORT; Boeringer Mannheim, Castle Hill, Australia) that was previously calibrated. After the finger asepsis, by using 70% ethyl alcohol, a lancet device with an automatic trigger was used for puncturing the index finger. The subjects’ blood was drained into strips for specific analysis (heparinized capillary strips). Each blood sample was immediately pipetted into a test strip that was inserted into the instrument. All measurements were performed 48 hrs post-matches between 8:00 and 9:00 a.m. with a room temperature of 21ºC and a relative humidity of 65%.

Analysis of the upper limb movement was carried out by adigital camera with a frequency of 60 Hz(model DMC-FZ200, Panasonic, Osaka, Japan). Kinematic data was obtained by way of reflective spherical markers that were placed bilaterally on specific anatomical landmarks. The markers were secured with medical double-sided adhesive tape on: (a)the lateral wrist epicondyle (average point between the ulnar and the radial styloid process); (b)the elbow (lateral epicondyle of the humerus);and (c) the shoulder (clavicularacromion process). The elbow was the reference point. The decrease in the angle represented flexion and the opposite was considered extension.

Electromyographic (EMG) data for the pectoralis major (PM,)the anterior deltoid (AD), the lateral head of the triceps brachii(TB), and therectus abdominis (RA)were collected during the experimental procedure. Electrodes were placed according to the recommendations of Cram et al.(2). For the PM, the electrodes were placed midway between the axilla and the areola. For the AD, electrodes were placed approximately 4 cm below the clavicle parallel to the musclefibers of the AD. For the TB, the electrodes were placed parallel to the muscle fibers about 2 cm laterally from the midline of the arm, and about 50% from the distance between the acromion and the olecranon process. For the RA, the electrodes were placed 3 cm apart and parallel to the muscle fibers of the RA so that they were located ~2 cm lateral and across from the umbilicus over the muscle belly.

Before experimental procedure got underway,the epilation and antisepsis procedures were performed on the areas where the bipolar surface electrodes were about to be placed.Skin preparation for all electrodes included removal of dead epithelial cells with an abrasive paper around the designated areas that was followed by cleansing with an isopropyl alcohol swab.The electrodes were placed on the right side of the subjects’ body. After electrode positioning, impedance measures wereassessed and accepted with less than 5kΩ. Impedance was observed using a signal frequency of 25 Hz. For acquisition of muscle activity, EMG signals were collected using a MyoSystemTM 1400A with 8 input channels. EMG signal was filtered with a band pass between 20 and 450Hz. Sampling rate of the signal was 1000 Hz. For proper comparisons, the RMS value (Root Mean Square) obtained for each muscle (PM, AD, BB, and RA) was normalized to the maximum voluntary isometric contraction (MVIC) values ​​obtained before the workout.Signal intensity was presented as a percentage of the MVIC (12).Each set was fragmented in three phases and analyzed, start (second contraction), middle (fifth contraction), and end (penultimate contraction).Anthropometric measurements consisted of height, body mass, and body fat.

Statistical Analyses

The Shapiro-Wilk test and sphericity (Mauchly test) showed that all variables presented normal distribution and homoscedasticity.Intraclass correlation coefficient showed high relation between test and retest (ICC=0.98). Mixed model repeated analysis [sets], when a significant F level was identified, a least significant difference (LSD)post hoc test was performed to locate pair-wise mean differences. Level of statistical significance was set at P≤0.05 for all tests. Statistical analysis was performed with SPSS version 20.0 (Chicago, IL, USA).

RESULTS

There were statistical differences between sets for elbow flexion (P=0.001), set 1 was higher than set 2(P<0.020) and set 3 (P<0.01). There was nostatistical difference on elbow extension (P>0.05) (refer toFigure 1a). Blood lactate concentrated showed an increase acrosssets. Set 3 was higher than rest, set 1 and set 2, (P=0.01);Moreover, set 2 was higher than set 1 and rest (P<0.05), and rest was lower than set 1 (p<0.01).Absolute load volume was lower in set 3 compared with set 2 (P=0.01) and set 1 (P<0.01), andset 2 was higher than set 1 (P=0.02) (Figure 2c).

Figure1.Elbow Movement (a), Blood Lactate Concentration (b), and Load Volume during Three Sets onExperimental Protocol.*P0.05 for rest, #set 1, $set 2

The TB muscle showed decrease in the set 2 (P=0.026) and set 3 (P=0.04) compared to set 1 (refer to Figure 2c). Furthermore, the RA increased muscle activity in the end phase compared to the middle (P=0.002) and the start (P=0.001) phases (Figure 2d). There were nodifferences in muscle activityfor the PM andthe ADmuscles between sets (0.17 and 0.32) and phases (0.35 and 0.33) (Figure 2a and 2b).

Figure 2. %RMS Normalized of the PectoralisMajor (a), Anterior Deltoid (b), Triceps BrachiiLateral Head (c), and Rectus Abdominis (d) during Three Sets of Experimental Protocol. *P<0.01 for set 1,#P<0.01 for middle phase, and $start phase

DISCUSSION

The purpose of this study was to investigate the influence of a fixed rest interval of 2 min on volume load, and upper body myoelectric activity, range of motion and blood lactate after multiple sets during the bench press (BP) exercise.Confirming our hypotheses the fixed RI changed the ROM pattern in the upper limb during the sets. In addition, myoelectric activityon muscles of the shoulder and the elbow andblood lactate concentrated increased while the absolute volume load decreased.

According to the ACSM position stand(2), the RIof the multi-joint exercises should be 2 to 3 min in duration and the mono-joint exercises should be 1 to 2 min. However, it seems that the optimal rest interval for muscle recovery isexercise dependent (17). TheRI influences some performance indicators, such as the concentration of blood lactate that showed an increase acrossthe sets during the experimental procedure. A previous study (21) has indicated a local accumulation of metabolic (e.g.,lactate and hydrogen ion)that stimulatesan increase in thegrowth hormone (GH) (21), and yet themechanismto explain the relation between acid–base changes and GH secretion is unclear. Furthermore, the acute effects do not explain the chronic adaptations (20).

Metabolic responses and fatigue rate arecorrelated with the acute response to exercise. This relationship indicates an inverse relationship between the length of the time interval and the metabolic response of different time intervals (30 sec, 1, 2, 3, and 5 min) (17). Thus, a suitable interval time >3 min is important because of the related metabolic functions, particularly with regards to thesignificant 85% recovery of ATP-CP and theremoval of H+ and lactate (glycolytic metabolism), although total lactate removal takes 4and 10 min.

A shorterRI of <2 min may limit the magnitude of the individual's metabolic recovery, thus resulting in altered recruitment patterns of the muscles with an overall decrease in muscle strength (22). Our results showed a decrease in RMS for TB after set 1 and set 2, and no change in RMS of the PM and DA. Moreover, RMS of the RA increasedduring the end phase of sets (penultimate repetition). Changes in EMG amplitude have long been associated with fatigue, because blood flow within the muscle is maintained during the dynamic contraction by enhanced venous return from the contracting muscle, which suggest that muscle fiber conduction velocity (MFVC) and median frequency (MDF) were affected by the metabolic state within the muscle (12). Despite no totally elucidated mechanismsto explain the alterations in myoelectric activity during multiple sets, a possible explanation is the decrease in the potential conduction velocity of the muscle fiber beyond increase extracellular K+ and changes in pH (11).

The changesin blood lactate and EMG explain the decrease in volume load, given that the results showed 2 min was insufficient to maintain the volume loan. This finding agrees with the work of Richmond and Godard (16) who reported a reduction VL after multiples sets for trained men during BP with 75% of 1RM and a 1 min RIand Kraemer (10) who observed trained football players during3 sets of 10RM on BP compared 3 with 1 min RI (VL 1 <3 min). These results may be explain the decrease in elbow flexion between sets(set 1 flexed more than set 2 and set 3).

CONCLUSIONS

The findings indicate that the fixed rest interval had an influence on the subjects’ acute metabolic responses (blood lactate) and myoelectric activity of the TB and RA muscles.Thus, it is important for practitioners to consider the duration of the exercise rest interval when developing a RT program. We suggest a rest time >2 min for better performance in this specific exercise for multiple sets.

ACKNOWLEDGMENTS

The authors thank the Foundation for Research Support of the State of Amazonas (FAPEAM) for PhD scholarship conceded to EwerttonBezerra and MateusRossato. Futhermore, Coordination for the Improvement of Higher Education Personnel (CAPES) for the PhD scholarship conceded to Raphael Sakugawa.

Address for correspondence: Bruno Rafael Maciel Rodrigues, Esp. Federal University of Amazonas, General Rodrigo Otávio Jordão Ramos Av; 6200 - Coroado I, Manaus - AM, 69067-005. Email:

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