EXTERNAL AND INTERNAL FOCUS OF ATTENTION INCREASES MUSCULAR ACTIVATION DURING BENCH PRESS IN RESISTANCE-TRAINED PARTICIPANTS MATHIAS KRISTIANSEN,1 AFSHIN SAMANI,1 NICOLAS VUILLERME,1,2,3 PASCAL MADELEINE,1 AND ERNST ALBIN HANSEN1 1 Department of Health Science and Technology, Physical Activity and Human Performance Group, SMI, Aalborg University, Aalborg, Denmark; 2University of Grenoble Alpes, AGEIS, Grenoble, France; and 3University Institute of France, Paris, France ABSTRACT INTRODUCTION Kristiansen, M, Samani, A, Vuillerme, N, Madeleine, P, and Hansen, EA. External and internal focus of attention increases muscular activation during bench press in resistance-trained participants. J Strength Cond Res XX(X): 000–000, 2018— Research on the effects of instructed attentional focus during execution of strength training exercises is limited and has thus far only been performed on single-joint exercises. The aim of this study was to compare the effects of instructed internal (INT) and external (EXT) focus of attention with a baseline measurement of no instructed focus of attention (BASE) on the surface electromyographic (EMG) amplitude during a free-weight bench press exercise in resistancetrained participants. Twenty-one resistance-trained male participants performed bench press at 60% of their 3-repetition maximum, with BASE, EXT, and INT. The order of EXT and INT was randomized and counterbalanced. Electromyographic data were recorded from 13 muscles of the upper and lower body. Subsequently, mean and peak EMG amplitudes were computed. EXT and INT resulted in significantly increased mean EMG amplitude of 6 upper-body muscles as compared with BASE (p # 0.05). In addition, EXT and INT also resulted in increased peak EMG amplitude of 3 upperbody muscles as compared with BASE (p # 0.05). These results show that muscular activation is increased during bench press, when applying an instructed focus of attention compared with a baseline measurement with no focus instructions (BASE). KEY WORDS movement effectiveness, motor performance, strength training Address correspondence to Dr. Mathias Kristiansen, mvk@hst.aau.dk. 00(00)/1–10 Journal of Strength and Conditioning Research 2018 National Strength and Conditioning Association T he use of verbal instructions is common within training and exercise for facilitation of a specific movement. Depending on the formulation of the verbal instructions, the attentional focus of the athlete may be directed either internally or externally (40). On the one hand, an internal focus of attention encompasses the athlete focusing on the movements of his or her own body (36). An example is to focus on the contraction of the biceps brachii (BB) muscle (i.e., focal muscle) during a biceps curl exercise. On the other hand, an external focus of attention requires the individual to focus on the effects of his or her movement in relation to the environment (36). An example is to focus on the movement of the object being lifted during a biceps curl exercise. An external focus of attention has been shown to be superior to an internal focus of attention in terms of performance outcome in a variety of different sports disciplines such as golf (23,32,33), basketball (2,41), vertical jump (38,39), agility (L-run exercise) (24), discus throwing (42), volleyball (37), dart throwing (15,19,27), swimming (6), and gymnastics (1). An external focus of attention has also been reported to result in better running economy (26). As an explanation for the superiority of an external focus of attention, the constrained-action hypothesis has been proposed (22,35,36). Briefly, the constrained-action hypothesis suggests that an internal focus of attention interferes with automatic control processes. This interference presumably results in a constraint of the degrees of freedom of the motor system, thus compromising an effective execution of the motor task at hand. An external focus of attention, however, is believed to promote a more automatic and reflexive control process, resulting in improved motor performance (40). The effect of attentional focus has not been thoroughly investigated within the field of strength training. Strength training is one of the most widely practiced forms of exercise, being used to, for example, improve sports performance, change body composition, as well as rehabilitate musculoskeletal disorders and injuries (5). Furthermore, the use of verbal instructions is also a common practice in VOLUME 00 | NUMBER 00 | MONTH 2018 | Copyright ª 2018 National Strength and Conditioning Association 1 Focus of Attention During Bench Press strength training settings (3). In addition, some studies suggest that when not provided with verbal instructions, athletes seem to direct attention internally (18). Therefore, there is a need for more research in this area to determine which type of focus of attention is favorable in tasks requiring high force production. This is interesting with respect to optimizing sports performance and with respect to improving the instructions given to participants during experimental studies, just to mention a few examples. Lower surface electromyographic (EMG) activation of the BB muscle has been reported during biceps curls at the same load when adopting an external compared with an internal focus of attention (17,28). Because of the equivalent amount of external work being produced across focus conditions, the lower EMG amplitude during an external focus of attention has been interpreted as greater movement efficiency (17). However, the biceps curl is a relatively simple single-joint task, especially when performed in a dynamometer. There is currently no knowledge available on the effect of attentional focus on EMG activity during multijoint free-weight strength training exercises. Such exercises are characterized by being more difficult to execute, as well as resulting in an increased number of degrees of freedom. As an example, for proper execution of the commonly used exercise of bench press, the coordinated activation of all the major muscle groups in the legs, back, and upper body is required (11). Simultaneously, a considerable amount of focus should be directed toward controlling the heavy barbell in the desired movement trajectory. The sum of all these results in a dilemma in terms of where the focus of attention should be directed. For instance, one can choose to primarily focus on the focal muscles that are being activated (internal focus of attention). Alternatively, one can choose to primarily focus on the barbell that is being lifted (external focus of attention). If the constrained-action hypothesis is indeed valid, adopting an internal focus of attention during such a demanding task should have deteriorating effects on motor control, and consequently on performance. The aim of this study was to compare instructed internal and external focus of attention with no instructed focus of attention during a free-weight bench press exercise in resistance-trained participants. In particular, we focused on the EMG amplitude. We hypothesized that the internal focus of attention would result in higher EMG amplitudes compared with external focus of attention and a control condition. As the physical work performed across focus conditions was equal, a higher EMG amplitude would be interpreted as an indication of reduced movement efficacy (18). METHODS Experimental Approach to the Problem The bench press, which is one of the most popular and widely used strength training exercises, was chosen for this study, as proper execution of this exercise requires a coordinated 2 the activation of all major muscles of the legs, back, and upper body while handling a high load (10–12). The large number of phasic and postural muscles involved throughout the body makes bench press a complex bilateral arm movement and thus an appropriate strength training exercise for assessment of the effect of different instructed foci of attention. The study consisted of a familiarization session and a test session. The goal of the familiarization session was to familiarize the participants with the test protocol, laboratory environment, and test equipment, as well as to minimize learning effects in the subsequent test session. One week after the familiarization session, all participants performed the test session in which they were tested extensively in bench press. Testing was performed to address the role of internal and external focus of attention on EMG amplitude of 13 muscles during bench press. Subjects Twenty-one male participants (age 24.5 6 2.2 years [mean 6 SD], range 21–28, height 1.81 6 0.07 m, body mass 89.0 6 12.8 kg, and 3-repetition maximum [3RM] in bench press 109.4 6 25.9 kg) were recruited for participation in the current study. All participants had performed full-body strength training for at least 2 years, with 2–3 training sessions per week. The study was approved by the local ethics committee of the North Denmark region (N-20120036), and all participants gave their written informed consent after having been explained the experimental methods and risks. The participants in the current study are the same as the ones involved in a previous study from our group, focusing on reliability of muscle synergies during bench press (12). Therefore, the number of participants was determined using an a level set to 0.05, b level to 0.20, p0 to 0.7, p1 to 0.9, and n to 2 (30). p0 and p1 denotes the minimally acceptable level of reliability and the expected level of reliability, respectively. a level and b level denotes the probability of making a type 1 and type 2 error, respectively. Procedures The test session consisted of the following: mounting of electrodes, warm-up, a 3RM test in bench press, one set of 3 repetitions at 75% of the 3RM load for normalization purposes, and 12 sets of 8 repetitions at 60% of the 3RM load. Before mounting the electrodes, the skin areas covering the muscles of interest were shaved, abraded, and cleaned with alcohol. Surface EMG electrodes (Ambu Neuroline 720 01-K/12, Ag/AgCl, interelectrode distance 20 mm, Ambu A/S, Ballerup, Denmark) were mounted on the skin over the following muscles on the right side of the body: pectoralis major (PM), anterior deltoideus, BB, triceps brachii lateral head (TBL), triceps brachii medial head (TBM), latissimus dorsi (LD), erector spinae (ES), rectus femoris (RF), biceps femoris (BF), gastrocnemius lateral head (GML), soleus (SOL), vastus lateralis (VL), and vastus medialis (VM). All electrodes were mounted along the muscle fiber direction in TM Journal of Strength and Conditioning Research Copyright ª 2018 National Strength and Conditioning Association the TM Journal of Strength and Conditioning Research | www.nsca.com a bipolar configuration. Most of the electrodes were mounted according to the SENIAM recommendations (7). For PM and LD (not listed in the SENIAM recommendations), the electrodes were mounted 4 fingerbreadths below the clavicle, medial to the anterior axillary border, and 3 fingerbreadths distal to and along the posterior axillary fold, parallel to the lateral border of scapula (14), respectively. A reference electrode was mounted on the ankle, at the ipsilateral lateral malleolus. The impedance level of the electrodes was checked before proceeding. Electrodes were replaced in case of an electrode-skin impedance .10 kV. Furthermore, an interelectro distance of 20 mm was chosen in line with SENIAM recommendations to ensure SEMG selectivity and thereby reduce cross talk (7). After the placement of the electrodes, participants performed a progressive warm-up regimen by lifting increasingly heavier loads in bench press. Bench press was performed using an ER-Equipment power rack (ER Equipment, Albertslund, Denmark). Subsequent for the 3RM test, the load was increased by 2.5–10 kg per set of 3 repetitions, until 3RM was found. On average, 4 sets were required for the determination of the 3RM. A 4-minute rest was applied between all sets to avoid development of muscle fatigue (10). After successful completion of the 3RM test, the load was decreased to 75% of the 3RM load and a single set of 3 repetitions were performed. For this (and the 3RM test), participants were instructed to perform the eccentric phase in approx. 1 second and the concentric phase as fast as possible. The EMG data obtained during this set at 75% of the 3RM were used for normalization purpose (11). The 12 sets of 8 repetitions at 60% of the 3RM load included 4 different ways (I–IV, see below) of performing bench press. All sets were separated by 4-minute rest periods. To avoid the confounding use of previously instructed focus strategies, the sets described under I and II were always performed first (13,15,20,24). Thereafter, the sets described under III and IV were performed in a counterbalanced order. (I) Three sets of 8 repetitions were completed, in which the participants were carefully instructed to time the top and bottom position of the barbell to the auditory input of a metronome set to 1 Hz. This resulted in a 1second eccentric and a 1-second concentric phase. The objective of these sets was to practice this specific tempo of execution rigorously, so that it could be replicated during the latter sets without the use of auditory input. (II) Three sets of 8 repetitions were completed as a baseline measurement with no focus instructions (BASE). The objective of these sets was to maintain the same tempo, which had just been practiced. (III) Three sets of 8 repetitions were completed with an external focus of attention (EXT). The instructions to the participants before performing bench press with an EXT were as follows: “Perform 8 repetitions while moving the barbell up and down as smooth as possible and replicating the same tempo as you applied earlier. While performing the bench press, the focus of attention should be on the movement of the barbell. The movement of the barbell should be as smooth as possible.” (IV) Three sets of 8 repetitions were completed with an internal focus of attention (INT). The instructions to the participants before performing bench press with INT were as follows: “Perform 8 repetitions while moving the barbell up and down as smooth as possible and replicating the same tempo (1 Hz) as you applied earlier. While performing the bench press, the focus of attention should be on the contraction of your pectoral muscle. The concentric contraction and eccentric contraction of the pectoral muscle should be as smooth as possible.” All instructions were provided in detail by the same researcher for all subjects. Instructions were provided before each condition (I, II, and III) and repeated before each set. After each instruction, the subjects were asked to explain in their own words what they were supposed to do. If they failed in giving a satisfactory answer, the instructions were repeated. During all sets of bench press, a potentiometer (model KS60; NTT Nordic Transducer, Hadsund, Denmark) was connected to the middle of the barbell for measurement of the vertical position. This enabled the identification of the top and bottom positions of the barbell. To avoid any initial transition, the first bench press repetition of each set was removed from the data. This resulted in 21 repetitions per participant, for each condition of BASE, EXT, and INT. To evaluate the participants effort to adopt the instructed focus of attention, a 10-point numerical rating scale (NRS), ranging from 0 (completely uninvolved, not trying hard at all) to 10 (extremely involved, trying as hard as possible), was applied (29). Participants were asked to rate their effort to adopt the instructed focus of attention immediately after each set of EXT (III) and INT (IV). Data Recording and Processing. The EMG signals were recorded using an EMG amplifier (EMG-USB; LISiN— OT Bioelectronica, Turin, Italy). Electromyographic signals were amplified using an individual-specific gain factor (100–500) and band-pass filtered (10–750 Hz) before being sampled at 2,048 Hz. Furthermore, a notch filter (fourth order Butterworth band stop with rejection width of 1 Hz centered at the first 3 harmonics of the power line frequency of 50 Hz) was used to remove line interference. Electromyographic data were then segmented into 21 bench press cycles, using the data obtained from the potentiometer. A bench press cycle was defined as the period between 2 successive top positions (equivalent to one bench repetition per 2 seconds). The linear envelopes of the EMG signals across each of the 21 bench press cycles were obtained by low-pass filtering (zero-lag Butterworth, second order, 4 Hz) of the VOLUME 00 | NUMBER 00 | MONTH 2018 | Copyright ª 2018 National Strength and Conditioning Association 3 Focus of Attention During Bench Press rectified EMG. Each of the EMG envelopes was then interpolated into 100 time points, and the average for each time point across the 21 repetitions was calculated for each participant. The EMG amplitude at each time point was then divided by the normalization factor (see description below) obtained during the set performed at 75% of 3RM. Next, the mean EMG envelope was calculated in 10 consecutive epochs for each cycle. As a measure of mean amplitude across the entire cycle, the mean of the 10 EMG amplitude values was calculated. As a measure of peak muscle activity during the cycle, peak EMG amplitude was computed as the highest EMG amplitude value. To normalize the recorded EMG data, a task-specific submaximal dynamic normalization procedure was applied. This procedure has previously been used in a similar experimental setup (11). Briefly, the task-specific submaximal dynamic normalization procedure consisted of recording the maximal surface EMG envelope from the aforementioned muscles during the execution of a submaximal bench press at 75% of 3RM. The obtained value in this procedure was then used as a normalization factor. Two analyses were performed to check for the effects of fatigue in the data set. First, the mean and peak EMG amplitudes of all muscles obtained in III and IV were reordered independent of focus instruction, in the chronological sequence in which they were recorded. If fatigue was present, the latter EMG amplitudes should be higher than the former. Second, using the same chronological reordering sequence as described above, the time of execution of the first and the seventh repetition for all sets in II, III, and IV was calculated. If fatigue was present, the duration should increase between the first and the seventh repetition in each set and between repetitions of different sets. The seventh repetition was used instead of the eighth because the barbell was replaced in the bench press rack immediately after the eighth repetition, making the precise duration of this repetition difficult to reliably establish. Statistical Analyses Normal distribution of all data was evaluated using a Shapiro-Wilks test, histograms, and QQ-plots. For normally distributed outcomes, a 1-way repeated-measures Figure 1. Surface electromyographic (EMG) normalized envelopes from muscles of the upper body obtained during bench press with no instruction (BASE), external focus (EXT), and internal focus (INT). The EMG amplitudes were normalized with respect to the normalization factor obtained during a submaximal dynamic normalization procedure. The black bold line represents the mean profile for each group, whereas the thin lines represent the individual profiles. The cycle of the bench press is characterized as follows: 0% = start position with barbell above chest on straight arms. Fifty percent = bottom position, with barbell touching chest. Zero percent = start position. Hundred percent = end position, identical to start position. PM = pectoralis major, DA = anterior deltoideus, BB = biceps brachii, TBL = triceps brachii lateral head, TBM = triceps brachii medial head, LD = latissimus dorsi, ES = erector spinae. 4 the TM Journal of Strength and Conditioning Research Copyright ª 2018 National Strength and Conditioning Association the TM Journal of Strength and Conditioning Research | www.nsca.com analysis of variance (RM-ANOVA) with a Bonferroni post hoc test was applied to test for an effect of type of instructed focus of attention (i.e., BASE, EXT, and INT) on EMG amplitude. If the assumption of sphericity was violated, a Greenhouse-Geisser correction was applied. For the outcomes that were not normally distributed, a nonparametric statistical approach was applied. A Friedman test was used to test for an effect of type of instructed focus of attention (i.e., BASE, EXT, and INT) on EMG amplitude. A Wilcoxon signed-rank test was used as post hoc test. For NRS data, the 3 NRS scores obtained in EXT and INT, respectively, were averaged for each participant. A Wilcoxon signed-rank test was then used to test for differences between focus conditions. The reordered mean and peak EMG values of all muscles for the fatigue analysis were compared using a Wilcoxon signed-rank test. To test for differences in the time of execution of the first and last repetitions in all sets, a RMANOVA with a Bonferroni post hoc test was applied. A step-down Holm-Bonferroni adjustment was applied to all post hoc p values obtained, to retain the familywise error rate for multiple comparisons (8). The SPSS Version 23.0 (IBM Corp., Armonk, NY, USA) was used for all statistical analyses. Statistical significance was accepted at p # 0.05. Results are presented as mean 6 SD. RESULTS The peak and mean EMG amplitude of all muscles obtained in session III (independent of focus instructions) was not significantly different from the values obtained in session IV (p , 0.05). Likewise, there was no significant difference in time of execution of the first and last repetition of all sets performed across all focus types (BASE, EXT, and INT; p . 0.05). The NRS score was 8.9 6 0.8 for EXT and 8.7 6 0.9 for INT. The Wilcoxon signed-rank test showed no significant difference in the NRS score between EXT and INT (p = 0.537). All scores were on average above 8, which suggested that participants in general made a considerable and consistent effort in adopting the instructed focus of attention during all sets in bench press. Figure 2. Normalized surface electromyographic (EMG) envelopes from muscles of the lower body obtained during bench press with no instruction (BASE), external focus (EXT), and internal focus (INT). The EMG amplitudes were normalized with respect to the normalization factor obtained during a submaximal dynamic normalization procedure. The black bold line represents the mean profile for each group, whereas the thin lines represent the individual profiles. The cycle of the bench press is characterized as follows: Zero percent = start position with barbell above chest on straight arms. Fifty percent = bottom position, with barbell touching chest. Zero percent = start position. Hundred percent = end position, identical to start position. RF = rectus femoris, BF = biceps femoris, GML = gastrocnemius lateral head, SOL = soleus, VL = vastus lateralis, and VM = vastus medialis. VOLUME 00 | NUMBER 00 | MONTH 2018 | Copyright ª 2018 National Strength and Conditioning Association 5 Focus of Attention During Bench Press Mean Electromyographic Amplitude Individual EMG envelopes and the mean envelope across all participants, for all upper-body muscles and lowerbody muscles, are illustrated in Figures 1 and 2, respectively. A bar plot of the mean normalized EMG amplitude is depicted in Figure 3. The 1-way RM-ANOVA revealed a significant effect of instructed focus on the mean normalized EMG amplitude values of PM (p = 0.007), whereas the Friedman test revealed a significant effect for DA (p # 0.001), BB (p = 0.002), TBL (p = 0.035), TBM (p # 0.001), LD (p # 0.001), and ES (p = 0.010). Post hoc analyses showed that, for PM, the mean normalized EMG amplitude values were significantly higher for EXT (44.0 6 16.4%) than for BASE (40.7 6 15.6%) (p = 0.003). Besides, INT (43.9 6 16.6%) was not significantly different from BASE (p = 0.068) for PM. With regard to DA, the mean normalized EMG amplitude values were significantly higher for EXT (43.0 6 18.4%) and INT (43.3 6 18.5%) as compared to BASE (37.6 6 16.6%) (p # 0.001 and p = 0.002, respectively). With regard to BB, the mean normalized EMG amplitude values were significantly higher for INT (30.4 6 17.8%) as compared to BASE (27.7 6 16.0%) (p = 0.006). With regard to TBL, the post hoc tests did not reach statistical significance. With regard to TBM, the mean normalized EMG amplitude values were significantly higher for EXT (39.6 6 18.8%) and INT (40.3 6 19.2%) as compared to BASE (35.1 6 17.0%) (p # 0.001 and p # 0.001, respectively). With regard to LD, the mean normalized EMG amplitude values were significantly higher for EXT (40.0 6 16.8%) and INT (42.9 6 18.4%) as compared to BASE (36.2 6 15.8%) (p # 0.001 and p # 0.001, respectively). Besides, INT was also significantly higher than EXT (p = 0.028) for LD. With regard to ES, the mean normalized EMG amplitude values were significantly higher for EXT (24.2 6 14.6%) and INT (26.8 6 16.8%) as compared to BASE (22.3 6 13.9%) (p = 0.024 and p = 0.024). Besides, INT was also significantly higher than EXT (p = 0.025) for ES. No significant effect of instructions was found for the muscles of the lower-body RF (p = 0.625), BF (p = 0.596), Figure 3. Bar plot of the normalized EMG amplitude (mean + SD) obtained during bench press with no instruction (BASE), external focus (EXT), and internal focus (INT). *Significant difference (p # 0.05). PM = pectoralis major, DA = anterior deltoideus, BB = biceps brachii, TBL = triceps brachii lateral head, TBM = triceps brachii medial head, LD = latissimus dorsi, ES = erector spinae, RF = rectus femoris, BF = biceps femoris, GML = gastrocnemius lateral head, SOL = soleus, VL = vastus lateralis, and VM = vastus medialis. 6 the TM Journal of Strength and Conditioning Research Copyright ª 2018 National Strength and Conditioning Association the TM Journal of Strength and Conditioning Research | www.nsca.com GML (p = 0.554), SOL (p = 0.795), VL (p = 0.640), and VM (p = 0.554). Peak Electromyographic Amplitude With regard to the peak normalized EMG amplitude, the 1way RM-ANOVA revealed a significant effect of instructed focus for PM (p = 0.019), DA (p = 0.018), TBM (p # 0.001), and LD (p # 0.001). The post hoc analysis showed that, for PM, the peak normalized EMG amplitude was significantly higher for EXT (64.8 6 15.6%) as compared to BASE (61.5 6 14.0%) (p = 0.030). With regard to DA, the post hoc tests did not reach statistical significance. With regard to TBM, the peak normalized EMG amplitude was significantly higher for EXT (60.1 6 18.3%) and INT (62.7 6 18.5%) as compared to BASE (54.9 6 17.5%) (p # 0.001 and p # 0.001, respectively). With regard to LD, the peak normalized EMG amplitude was significantly higher for EXT (55.2 6 17.5%) and INT (57.2 6 19.9%) as compared to BASE (49.5 6 17.5%) (p # 0.001 and p # 0.001, respectively). No significant effect of instructions was found for the following muscles: BB (p = 0.269), TBL (p = 0.098), ES (p = 0.132), RF (p = 0.855), BF (p = 0.315), GML (p = 0.390), SOL (p = 0.661), VL (p = 0.615), and VM (p = 0.587). DISCUSSION In this study, EMG data were recorded from 13 muscles during bench press performed at 60% of 3RM, with 3 different foci of attention (BASE, EXT, and INT). We showed that EXT and INT resulted in significantly increased mean and peak EMG amplitudes of 6 upper-body muscles as compared with BASE. These results were mostly in contrast to our initial hypothesis and may suggest that, for resistancetrained participants at least, adopting either an external or an internal focus of attention reduces the movement efficacy during submaximal bench press. Previous studies in various force production tasks have shown that external focus of attention led to decreased muscular activity and increased performance compared with an internal focus of attention or a control condition of no instruction (16,20,21,28). For example, an external focus of attention decreased EMG activity of the antagonist muscle and increased performance in an isometric plantar flexion of the ankle (16). Similarly, compared with an internal focus of attention, an external focus of attention has been shown to increase force production and reduce muscular activity during an isokinetic biceps curl task (17) and to reduce muscular activity during a dynamic biceps curl task with a barbell using both a controlled and an uncontrolled tempo of execution (28). In a test to determine the maximal amount of repetitions that could be performed in the Smith machine bench press, during free-weight bench press, and during free weight squat, an external focus of attention improved performance in all 3 tasks compared with an internal focus of attention (20). In a more recent study, an external focus of attention significantly reduced muscular activity during an isokinetic concentric leg extension exercise compared with an internal focus of attention (21), whereas force output remained the same between the 2 focus conditions. Most research in this area has demonstrated an external focus of attention to be superior to either an internal focus of attention or a control condition of no instructed focus in terms of performance and movement efficacy (18,40). In the aforementioned studies (16,17,20,21,28), conclusions have been drawn on the effects of different foci of attention on performance by measuring force production. This study, on the other hand, compared EMG amplitudes recorded during bench press using the same weight in all sets, but with different foci of attention. While acknowledging that the focal point of this study and those of (16,17,20,21,28) was not identical, the results of this study do not support any benefit on applying an external focus of attention during bench press performed at 60% of 3RM. This discrepancy may be explained by the fact that the multijoint free-weight exercise used in this study is more challenging than performing a unilateral isokinetic biceps curl in a dynamometer or an isometric plantar flexion of the ankle. Thus, multiple degrees of freedom must be efficiently controlled to successfully complete the bench press. Furthermore, the participants in this study had a minimum of 2 years of strength training experience and a relatively high performance level (3RM = 109.4 6 25.9 kg), whereas most of other studies have recruited participants with either very little or no previous experience in the task that they were being tested on (34). In resistance-trained individuals, such as those recruited for this study, considerable adaptations are bound to have occurred in the motor control of the neuromuscular system through years of training, for the participants to attain such an efficient solution for controlling the multiple degrees of freedom (11). For resistance-trained individuals with extensive muscle strength and experience, it is therefore plausible that any focus of attention, which is markedly different from what they are used to, will act as a perturbation. This may in turn decrease the movement efficacy as reflected in this study by the significantly higher EMG amplitude of the upper-body muscles, when either an external or internal focus of attention was applied (Figure 3). An alternative explanation for the results is that the complexity of the instructions given in EXT and INT was higher compared with BASE. More specifically, the subjects had to focus on both the tempo of execution combined with either an external or internal cue in EXT and INT, while only focusing on the tempo of execution in BASE. The decreased movement efficacy in EXT and INT compared with BASE could then be explained by the complexity of the instructions given resulting in an increased mental load affecting the EMG amplitude (9). However, the idea that highly skilled athletes may not benefit from an external focus of attention is supported by a previous study (34) in which balance measures were investigated in world-class acrobats. While standing on an inflated rubber disk, the acrobats showed no VOLUME 00 | NUMBER 00 | MONTH 2018 | Copyright ª 2018 National Strength and Conditioning Association 7 Focus of Attention During Bench Press differences in postural sway among the 3 focus of attention conditions (control condition, external focus of attention, and internal focus of attention), but automaticity (as measured by the mean power frequency of their center of pressure movements) was perturbed by the external and internal focus of attention instructions. Similar results were found in performance of expert dart players, where performance deteriorated when an external or internal focus of attention was applied compared with baseline measurements consisting of dart throws with no instructions on focus of attention (25). And finally, the level of experience has also been shown to play a role in sprinting performance, as collegiate soccer players benefit from an external focus of attention during a 10-m sprint, while highly experienced sprinters do not (31). The constrained-action hypothesis has been proposed as an explanation for the superiority of an external focus of attention (22,35,36). Thus, it has been inferred that an internal focus of attention interferes with automatic control processes, whereas an external focus is believed to promote a more automatic and reflexive type of control, resulting in improved motor performance (22,35,36). With regard to our results, it seems, at least for the participants in this study, that when participants already have developed a focus of attention through rigorous practice, this particular focus of attention promotes a more automatic and reflexive type of control, resulting in optimal movement efficacy, whereas any new type of focus of attention, whether it be external or internal, seems to interfere with automatic control processes. A decreased EMG amplitude has, thus, previously been used to advocate for a more efficient motor strategy, when the external force produced was kept constant between focus conditions (17,28). Continuing this line of argumentation, our results clearly indicate that, for resistance-trained participants, an acute change in the focus of attention induced by instructions does not promote more efficient motor strategies compared with a control focus of attention (BASE). To the best of our knowledge, only one other study has provided similar results in which the control condition yielded better outcomes than either an instructed external or internal focus of attention (34). There was no significant effect of different foci of attention on muscle activity of the lower body. When creating a stable setup in the bench press exercise, plantar flexors of the ankle joint and knee extensor muscles are activated to push the lower body in the vertical direction. This increases stability and stiffness of the whole body, thereby creating a rigid base from which maximal strength of the upper body can be expressed. The isometric contractions produced by these muscles during bench press did not seem to be affected by different attentional foci. This may be because this is an essential part of performing the bench press for the resistance-trained participants recruited for this study (11), or because the activity of the lower-body muscles remain unaffected, when the focus of attention is directed at or toward part of the upper body. These results are in contrast 8 the to previous studies, which suggest the effects of focus of attention to be general in nature, and to be able to “spread” to muscle groups that are not in the performers focus of attention (41). There are some limitations to this study. First, the lifting intensity was submaximal (60% of 3RM). Thus, it is unknown whether or not the results would have been the same, had an intensity closer to a 100% of 1RM been used. This was, however, a very deliberate choice to avoid muscle fatigue during data recording as fatigue causes the EMG amplitude to increase (4). Second, the tempo of execution was rehearsed before data collection using a metronome to control for the effects of different velocities on the recorded EMG data. As this tempo of execution may have been different from the preferred tempo of execution, this could potentially affect the results. Furthermore, as the objective in the baseline measurement (II) was to maintain the same tempo that had been rehearsed, focusing on the tempo of execution could be interpreted as a sort of an external focus. In that case, the results of this study demonstrate differences in EMG amplitude between an external focus on the movement of the barbell, an internal focus on the pectoral muscle and an external focus on the tempo of execution. Third, in this study, the external focus of attention instructions was focused on the movement of the barbell, and the internal focus of attention instructions were focused on the contraction of the pectoral muscle. As the formulation of the instructions can have profound effect on the outcome (40), it is possible that other external and internal focus instructions, for instance, focusing on pushing against the barbell or focusing on the movement of the arms, respectively, could have yielded different results. Finally, given this study design, the baseline trials always preceded the external and internal focus of attention trials. As mentioned in the methods, the applied study design did not randomize the BASE sets to avoid the confounding use of previously instructed focus strategies (20). It is unlikely that accumulated muscle fatigue occurred given the low intensity of lifting (60% of 3RM) coupled with the 4-minute interset rest intervals and the training status of the participants. Subsequent analyses suggested that muscle fatigue was not present in the data set, as the peak and mean EMG amplitude of all muscles obtained in session III (independent of focus instructions), was not significantly different from that obtained during session IV. Furthermore, comparing the time of execution of the first repetition and the last repetition of all sets performed across all focus types (BASE, EXT, and INT) showed no significant differences. These underlined a lack of carryover effect over the sessions of bench press and the absence of fatigue development. The authors acknowledge that the procedure of always recording the baseline trials before the external and internal focus of attention trials, in theory, could generate a statistical order effect. However, this procedure has previously been used in several studies, with the aim of avoiding the confounding use of previously instructed focus TM Journal of Strength and Conditioning Research Copyright ª 2018 National Strength and Conditioning Association the TM Journal of Strength and Conditioning Research | www.nsca.com strategies (13,15,20,24), which, in the opinion of the authors, would have been detrimental to the results of this study. In conclusion, this study demonstrated that adopting either an internal or an external focus of attention during bench press significantly increased the mean and peak EMG amplitude in PM, DA, BB, TBM, LD, and ES muscles of the upper body among resistance-trained participants, when compared with a control condition of no instruction. These results suggest that movement efficacy during bench press can be deteriorated, when adding a focus of attention that is different from the focus of attention used during a control condition of no instructed focus (BASE). PRACTICAL APPLICATIONS This study provides valuable information on the effects of instructed focus of attention during submaximal bench press in resistance-trained participants. Our results show that, for participants with considerable strength training experience, adopting either an external or an internal focus of attention reduces the movement efficacy during submaximal bench press, as measured by EMG amplitude. It is important to note that this study design does not allow conclusions to be drawn on the long-term training effects of incorporating either an external or internal focus of attention. ACKNOWLEDGMENTS 10. Kristiansen, M, Samani, A, Madeleine, P, and Hansen, EA. 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How changing the focus of attention affects performance, kinematics, and electromyography in dart throwing. Hum Mov Sci 29: 542–555, 2010. 16. Lohse, KR, Sherwood, DE, and Healy, AF. Neuromuscular effects of shifting the focus of attention in a simple force production task. J Mot Behav 43: 173–184, 2011. 17. Marchant, DC, Greig, M, and Scott, C. Attentional focusing instructions influence force production and muscular activity during isokinetic elbow flexions. J Strength Cond Res 23: 2358–2366, 2009. 18. Marchant, DC. Attentional focusing instructions and force production. Front Psychol 1: 210, 2011. 19. Marchant, DC, Clough, PJ, Crawshaw, M, and Levy, A. Novice motor skill performance and task experience is influenced by attentional focusing instructions and instruction preferences. Int J Sport Exerc Psychol 7: 488–502, 2009. ER Equipment is thanked for loan of the lifting equipment. This study was supported by the Danish Rheumatism Association. 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