Smith Machine vs. Barbell: ten repetition maximum loads and muscle activation pattern during upper body exercises.
The process of individualizing workout is important. Before choosing parameters such as exercise intensity, numbers of repetitions, speed of execution, rest intervals, and weekly frequency, exercise physiologists and other healthcare professionals involved with strength training should choose the type of exercise to be performed. Exercise selection should be a priority because the focus of the strength training program depends on making the right decision. Is the purpose of the strength training program to develop hypertrophy and maximum strength or muscular endurance and, if so, for which muscles? For example, the standard upper body resistance exercises for the development of anterior shoulders muscles are the bench press, military press, and close-grip bench press.
In addition to specific exercises for specific muscle groups, there are different ways to execute free weight (i.e., barbell or dumbbells) exercises versus using machines (i.e., cables or the Smith Machine) and there are different effects as well. For example, when Krosshaug (6) analyzed the bench press exercise using dumbbells and barbell, it was found that during the execution of the bench press with the barbell, the external reactive forces had a medial-lateral factor due to friction. This outcome did not happen with the dumbbells execution, where the external reaction forces were transmitted through the grip straight downward due to gravitational pulling. Furthermore, it seemed to change the triceps brachii activation during the barbell bench press (4,10), perhaps, due to the fact that the barbell bench press exercise required less stabilization of the shoulder musculature since the vertical force was distributed at the midpoint of the bar (5).
Saeterbakken et al. (10) observed the greatest values for maximal strength during the barbell bench press exercise when compared with the same exercise executed with dumbells and the Smith Machine. These data corroborate with Krosshaugm (6), when the author showed lower activation levels for the triceps brachii during dumbbells execution. Several researches were made related to the bench press, but the same have not happened to the others exercises. Paoli et al. (8) observed the influence of different range of motion in shoulder muscle activity during military press exercise. They suggested changes in muscle activity of trapezius (upper and middle) during incomplete range of motion. Nevertheless, according our research, there is no study about muscle activity during the close-grip bench press when performed with dumbbells and the Smith Machine.
Literature is narrow concerning the influence of different types of execution (barbell or Smith Machine) for distinct exercises involving shoulder and elbow muscle activation patterns. Furthermore, there is a lack of information about how to combine exercises in different phases of a periodized exercise program. No studies to date have analyzed and compared muscle activation patterns over different sorts of execution (barbell or Smith Machine) for the bench press, military press, and close-grip bench press. We hypothesized that barbell will be more effective for shoulder and elbow muscles than the Smith Machine for all exercises, but for maximum strength performance.
Hence, the purpose of this study was to investigate muscle activation and ten repetition maximum load determination for exercises (bench press, military press, and close-grip bench press) performance between barbell and the Smith Machine with recreationally trained men.
Twelve recreational trained men (mean [+ or -] SD: 21.83 [+ or -] 4.5 yrs; 1.72 [+ or -] 0.1 cm; 80.3 [+ or -] 9.2 kg; 25.1 [+ or -] 2.96 kg x [m.sup.-2] ; 17.3 [+ or -] 6.85 %Fat), nonprofessional bodybuilders, training 3 times x [wk.sup.-1] during less than one year participated in this study. Subjects reported no shoulder injury or pathology at the moment of the experiments and during the previous six months. The study was approved by the Ethics committee of the Federal University of Amazonas--Brazil (CAAE: 15313413.4.00005020). All participants were asked to read and sign an informed consent about the tests.
A within-subject, randomized and counterbalanced repeated-measures design was used to analyze the 10-RM strength and muscle activation in the bench press, military press, and the close-grip bench press. Two types of exercise execution were adopted (barbell and Smith Machine) for three upper body exercises: bench press, military press, and the close-grip bench press. 10-RM load was determined for each subject for the exercises in three sessions, with 48 hrs between sessions, and in randomized order: two exercises for sessions, with 20 min between exercises. All machine-based exercises were performed on a RS-Rotech equipment (Rotech Company, Goias, Goiania, BRA). During 10-RM testing, subjects were given a maximum of three attempts for each exercise a day, with a 5-min rest between attempts (9). A metronome conducted the exercise execution speed at a constant rhythm of four seconds per repetition (2 sec for concentric phase and 2 sec for eccentric phase) (5).
Electromyographic (EMG) data for the pectoralis major, anterior deltoid, triceps brachii, and biceps brachii were collected during all exercises with the barbell and the Smith Machine. Electrodes were placed according to the recommendations of Cram and colleagues (2). For the pectoralis major muscle, the electrodes were placed midway between the axilla and the areola. For anterior deltoid, the electrodes were placed approximately 4 cm below the clavicle parallel to the muscle fibers. For the biceps brachii, the electrodes were positioned on the midpoint of the muscle belly, in the longitudinal direction of the fibers. For triceps brachii, the electrodes were placed parallel to the muscle fibers, about 2 cm laterally from the midline of the arm (i.e., half way between the acromion process and the olecranon process).
Before the experimental procedure, epilation and antisepsis procedures were performed on the areas the bipolar surface electrodes were to be placed (Kendal Medi Trace 200; Tyco Healthcare, Pointe-Claire, Canada). The electrodes were placed on the subjects' right side of the body. After electrode positioning, impedance measures were assessed and accepted with less than 5 k[ohm]. The 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. The EMG signal was filtered with a band pass between 20 and 450 Hz. The sampling rate of the signal was 1000 Hz. For proper comparisons, the RMS value (Root Mean Square) obtained for each muscle (pectoralis major, anterior deltoid, biceps brachii, and triceps brachii) was normalized to the peak values obtained relative to all exercise modes. The signal intensity was presented as a percentage of the peak (11).
The Shapiro-Wilk test and homogeneity (Levene's test) showed that all variables presented normal distribution and homogeneity. The intraclass correlation coefficient showed high relation between test and retest for all exercise and different execution modes (ICC>0.9). Paired f-student test compared the muscle action between BA and SM for all exercises. The level of statistical significance was set at P [less than or equal to] 0.05 for all tests. The statistical analysis was performed with SPSS version 20.0 (Chicago, IL, USA).
There were statistical differences between the barbell and the Smith Machine for the military press and the close-grip bench press during the 10-RM test (P=0.006; P=0.030), respectively. However, the same did not happen for bench press (P=0.32), Figure 1.
[FIGURE 1 OMITTED]
No significant differences on muscle activity were observed for the pectoralis major, anterior deltoid, triceps brachii, and the biceps brachii when comparing the exercises performed with the barbell and the Smith Machine (P>0.05). The pectoralis major showed activity with values above 50% (RMS normalized) for the bench press [barbell, (54.77 [+ or -] 11; Smith Machine (51.24 [+ or -] 11)] and the close-grip bench press [barbell, (53.14 [+ or -] 10)]. The anterior deltoid showed similar muscle activity values of the pectoralis major for the bench press [Smith Machine, 52.25 [+ or -] 19) and the military press [barbell (58.19 [+ or -] 13); Smith Machine (60.74 [+ or -] .2)]. The triceps brachii showed more activity (50%, RMS normalized) than the biceps brachii during the bench press and the military press, but similar values in the close-grip bench press (refer to Figure 2).
[FIGURE 2 OMITTED]
The purpose of this study was to investigate maximum 10-RM loads determination and muscle activation for bench press, military press, and close-grip bench press performance using the barbell and the Smith Machine with recreationally trained men. We hypothesized that barbell would be more effective for shoulder and elbow muscles than the Smith Machine for all exercises, but for maximum strength performance. Our hypothesis for maximum strength performance during 10-RM was confirmed, because the military press and the close-grip bench press showed higher values while using the Smith Machine than when using the barbell. For 10-RM strength, the military press and the close-grip bench press executed with the Smith Machine, which had the lowest joint stability requirements, showed higher results than the same exercises when using the barbell, 6% and 5%, respectively. However, the load lifted in the bench press was similar between the analyzed conditions.
In agreement with our findings are Behm and Kenneth (1). They reported that during the Smith Machine performance, the stability requirements were lower, which required a greater application of force. Also, the subjects' experience in strength training may have had an influence on our results. On the other hand, Saeterbakken et al. (10) disagree with the present study. Their findings showed lower performance when comparing the Smith Machine and the barbell. Here again, though, their subjects were more experienced (~4 yrs) than the subjects in the present study.
The second part of our hypothesis was rejected since the findings showed that the possible instability did not induce higher muscle activation during the barbell exercise. The pectoralis major and the anterior deltoid muscles did not show a difference for the bench press. Similar results were presented by McCaw and Friday (7), who found no significant differences in the integrated electromyographic activity (iEMG) of the pectoralis major and the anterior deltoid muscles when comparing 80% 1-rM for the bench press exercise using the barbell and the Smith machine.
During the military press, greater shoulder abduction promoted higher activity of the anterior deltoid (~60%). These results corroborate with Paoli et al. (8). The researchers examined the effect of ROM [the first one with a final elbow angle of 90o (R1); the second with 135o (R2), and the last one with a final elbow angle of 180o (R3)] at different loads (no load, 30% of one repetition maximum [1-RM], and 70% of 1-RM) on the electromyographic (EMG) activity of the pectoralis major, anterior deltoid, and triceps brachii. The results showed that the use of the widest ROM increased the EMG activity of all the muscles selected with respect to the closest one; whereas, this effect is not totally confirmed with the employment of R2. The lower activity of the pectoralis major (~40%) can be explained by the fact that the sternal portion evaluated is not involved with shoulder abduction.
However, during the close-grip bench press performance, greater shoulder flexion was evident with involvement from both the anterior deltoid and the pectoralis major. Both the biceps brachii (a shoulder flexor) and the triceps brachii (an elbow extensor) were at ~50%. Saeterbakken et al. (10) investigated the influence the dumbbell exercise in addition to the barbell and Smith Machine and Dumbbell. They found a difference in the biceps brachii and triceps brachii involvement only between the barbell and the Smith Machine when compared with dumbbells, in which the muscle activity of triceps brachii was lower and the biceps brachii was higher than the others.
No difference was observed in muscle activity for the pectoralis major, anterior deltoid, biceps brachii, and triceps brachii when comparing the barbell and the Smith Machine. However, significant differences in 10-RM loads were observed between the barbell and the Smith Machine for the close-grip bench press and the military press exercises. These finding should be important when considering the determination of training loads.
Foundation for Research Support of the State of Amazonas (FAPEAM/Brazil) providing financial support PhD scholarship (Ewertton Bezerra and Mateus Rossato) and for scientific initiation scholarship (Iago Pimentel).
Address for correspondence: Ewertton Bezerra, Federal University of Amazonas, General Rodrigo Otavio Jordao Ramos Av; 6200--Coroado I, Manaus--AM, 69067-005. Email: firstname.lastname@example.org
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(10.) Saeterbakken AH, Tillaa R, Fimland MS. A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements. J Sports Sci. 2011 ;29(5):533-538.
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Iago Pimentel , Ewertton Bezerra [12,3], De Angelys de Ceselles [2,3], Mateus Rossato [1,2], Joao Machado , Caetano Lazzari , Gabriel Paz , Humberto Miranda , Antonio Moro 
 Biomechanics Laboratory--Federal University of Santa Catarina, SC, Brazil,  Human Performance Laboratory--Federal University of Amazonas, AM, Brazil,  Strength Training Laboratory, Federal University of Rio de Janeiro, RJ, Brazil
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|Author:||Pimentel, Iago; Bezerra, Ewertton; de Ceselles, De Angelys; Rossato, Mateus; Machado, Joao; Lazzari,|
|Publication:||Journal of Exercise Physiology Online|
|Date:||Oct 1, 2016|
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