In strength training for different sports, the bench press is one of the most popular exercises for the upper body. This exercise is typically performed with a barbell while lying supine on a bench. The barbell is first lowered to the chest and afterward is pushed up again until the arms are fully extended. The maximal performance is measured as the maximal barbell mass that is lifted to full elbow extension. Several studies have been published in which bench pressing is used to enhance strength (i.e., the maximal force that one can apply to an object) of the upper extremities in ball sports (e.g., [1,2,4]). It has also been reported that maximal one repetition maximum (1RM) in bench press, as an indication of upper body strength, correlates positively with throwing performance in experienced team handball players (7).
A few studies reported changes in velocity, force, and power during the lift (e.g., [7-9]). Madsen and McLaughlin (6) and Newton et al. (9) found that at maximal and submaximal loads, a decrease of velocity occurs after the initial velocity in the upward movement, followed by an increase again after this point. This particular point, the first local minimum of the upward velocity (T Vmin), is also-called the sticking point (6,8). Newton et al. (9) reported that this point occurred in loads of 90% of 1RM but not for 75% of 1RM load. Madsen and McLaughlin (6) reported the presence of the sticking point at 1RM. They (6) suggested that the sticking point might be the weakest point in the bench press exercise. Lander et al. (5) reported a sticking period that was defined as the period from the peak velocity to the minimal velocity (i.e., sticking point) in the ascending part of bench press. They postulated that failure is most likely to occur during this period because the lifter's applied force is below the magnitude of the bar's weight. The existence of such a period was also identified by Elliott et al. (3) and van den Tillaar and Ettema (10).
van den Tillaar and Ettema (10) found that activity increased significantly only in the major pectoralis muscles and the anterior part of the deltoid muscles during the upward movement. Furthermore, they reported that the occurrence of the peak muscle activity follows a sequence of first the biceps (just before the start of the upward movement) followed by the peak activity of the triceps. The pectoralis and deltoid muscles had their peak activity around the T Vmin (10). They proposed that the sticking period occurs, not because of a lack of mechanical muscle strength per se, but because muscle force capacity is diminishing, requiring an increase of muscle activation, which occurs with some delay (10). The diminishing force capacity is a direct consequence of the waning effect of the eccentric part in a stretch-shortening contraction (e.g., 11). Thus, in accordance with Lander et al. (5), it was hypothesized that the sticking period, rather than the sticking point, is the weakest link in the upward movement. In other words, the sticking period is likely the period at which an attempt potentially will fail. In such a case, the sticking point would not be reached during a failed attempt. Instead, the upward movement would come to a complete stop without any (temporary) increase in upward velocity. Therefore, the purpose of this study was to examine the kinematics and muscle activity in the successful maximal 1RM and unsuccessful at 1RM + 2.5 kg bench presses. It was hypothesized that potential failure would occur in the sticking period and that T Vmin (the sticking point) would not be reached in failed attempts. Furthermore, we predicted that the amount of muscle activity in the major pectoralis, biceps, triceps, and the anterior part of the deltoid muscles is the same during the different periods in unsuccessful attempts when compared with successful attempts. The rationale was that, in failed attempts, muscle activity has already reached (near) its maximum value before the sticking period because of the excessive mass that must be carried. Muscle activity thus cannot increase (enough) during the sticking period to overcome the fading of the force capacity. Thus, failure must occur.
Eleven male subjects were recruited from students in sport science (age = 21.9 ± 1.8 yr, mass = 80.0 ± 11.2 kg, height = 1.79 ± 0.08 m). All subjects had at least 1 yr of bench press training experience. Before participating in this study, they were fully informed about the protocol, and informed consent was obtained before all testing in accordance with the approval of local ethical committee and current Norwegian law and regulation.
After a general warm-up, which included jogging and drills for the upper body, the subjects underwent a standardized protocol with bench pressing. They began by pressing a barbell (20 kg) 40 times. Next, they performed two series of six repetitions at 40% of the assumed 1RM, one series of three repetitions at 60%, one series of two repetitions at 75%, and one series of two repetitions at 85% of the assumed 1RM. The assumed 1RM was set according to the information given by the subjects on maximal lifts performed in the previous 6 months. There was a pause between the series of approximately 3 to 5 min to avoid possible fatigue. Finally, in this series, the assumed 1RM was carried out. When successful, an attempt with an additional 2.5 kg was tried until the first attempt that was unsuccessful. When the attempt at the assumed 1RM was unsuccessful, the mass was decreased by 2.5 kg per attempt until the real 1RM was found. A total of two attempts, one successful at real 1RM and one unsuccessful at real 1RM + 2.5 kg, were used for further analysis. Six subjects assumed their 1RM correctly; for three others, the real 1RM was 2.5 kg greater than the assumed, whereas for the remaining two subjects, the real 1RM were 2.5 kg and 5 kg less, respectively. Fatigue was avoided by a pause of around 5 min between all attempts after the first assumed 1RM attempt. It was not allowed to "bounce" the barbell off the chest, to pause at the transition between the descending (countermovement) and the ascending (goal-directed movement) part of the bench press, or to raise the lower back from the bench.
Three-dimensional positions of the joints and limb segments were measured using a motion capture system (Qualysis, Gothenburg, Sweden) with eight cameras (500 Hz) that tracked the position of the reflective markers (2.6 cm in diameter) placed on the following anatomical landmarks on both sides of the body: upper part of the sternum, lateral tip of the acromion, lateral epicondyle of the elbow, and the styloid process of the ulna. The displacement of the barbell was measured by two markers on the middle of the barbell 20 cm from each other.
The horizontal shoulder adduction, shoulder abduction, and elbow flexion angles were calculated for the whole trial (Fig. 1).
Velocity and acceleration of the barbell were calculated using a five-point differential filter in MATLAB 7.0 (Mathworks, Natick, MA). The force that was developed on the barbell was calculated as the product of barbell acceleration and mass. The time point that the lowest barbell position occurred was defined as zero time (T 0). Thus, a negative time was a point in the downward movement and a positive time was a point in the upward movement. The resultant moment arms at the elbow and shoulder were calculated for the entire bench press action according to Elliott (3): the projected distances in the horizontal plane from the wrist (i.e., line of barbell weight) to the elbow joint and from the wrist to the shoulder joint (Fig. 1) were calculated for both the successful 1RM and the failed attempts.
Before the 1RM attempts were performed, EMG surface electrodes (DE 2.1; Delsys, Boston, MA) were attached on both right and left parts of the belly of the long head of the triceps brachii, the anterior deltoid, the sternal portion of the pectoralis major, and the biceps brachii. Thus, the activities of a total of eight muscles were measured. The electrodes were connected to a wireless EMG system (Myomonitor IV; Delsys). Before electrode placement, the skin was shaved and cleaned with alcohol, and a small amount of conducting gel was applied to each electrode to reduce impedance. The EMG signals were sampled at a rate of 1000 Hz. Using MATLAB 7.0, signals were band-pass-filtered (10-500 Hz, eighth-order Butterworth, recursive), rectified, and smoothed (moving average filter = 100-ms window width).
Three different maximal isometric contraction exercises were done to measure the maximal voluntary contractions (MVC) of the different muscles. We used isometric biceps and triceps curl movements to establish MVC activity for biceps and triceps, respectively. To establish maximal activity in the deltoid and pectoralis muscles, the subjects performed an isometric bench press at the lowest point (barbell was locked). Every isometric contraction was performed twice, and the highest activity averaged for 1 s was used for normalizing the muscle activity during the maximal bench press attempts. To locate possible differences in normalized muscle activity during the bench press movement, the average of the smoothed EMG signal was calculated for each of the four periods. The first period was from the maximal downward velocity (T Vdown) to the lowest barbell point (T 0): the eccentric period. The next period was from the lowest barbell point until the maximal barbell velocity (T Vmax): the presticking period. The third period was from the maximal barbell velocity until the first located lowest barbell velocity (T Vmin): the sticking period. The last period, the poststicking period, started at T Vmin and had the same time length as the presticking period. Although only intrasubject and intramuscle comparisons were made (paired comparisons), we used normalized values to ensure that the variance was limited as possible in the group data. It should be noted that the EMG-time profiles may have been strongly affected by changing muscle mass that was located directly under the electrodes. However, the main comparisons are not affected because this systematic artifact disappears in the comparisons.
Concerning changes in variables (EMG, joint movements, moment arms) during the bench press, the attempts were compared using a two-way (2 × 4) ANOVA (attempt: success-failure × period: eccentric, presticking, sticking, poststicking), with repeated measures on both factors. Interaction effects were of particular interest because these outcomes indicate differences between the two attempts in how the signals change over time. In addition, to identify differences between successful and unsuccessful performances at particular moments during the bench press, and disregarding the changes in a signal, a paired t-test was conducted between the outcomes of the two performances. In cases where sphericity could not be assumed, the Greenhouse-Geisser correction was applied. The level for significance was set at P ≤ 0.05.
The average mass that was lifted successfully at 1RM was 97.73 ± 15.8 kg. The unsuccessful attempts were performed at 103% of 1RM. In both attempts, a sticking period occurred. In unsuccessful attempts, five subjects stopped their attempt during the sticking periods, while the other six subjects continued lifting, but had to give up later during the attempt. Figures 2 and 3 show an example of changes in the vertical height, velocity, resultant moment arms, and joint angles.
The peak force at both attempts (successful = 1250 N, unsuccessful = 1241 N) and the force at the transition from descent to ascent, T 0 (Table 1), were similar. Because of the mass difference, this resulted in a significant difference in peak acceleration (2.84 vs 2.41 m·s−2) and maximal velocity (0.24 vs 0.19 m·s−1) of the barbell (Table 1 and Fig. 2). Again, this resulted in a significantly lower height at T Vmin in the unsuccessful compared with the successful attempt (Table 1 and Fig. 4). As a consequence, significantly smaller joint angles for the elbow flexion (P = 0.002) and the horizontal shoulder adduction (P = 0.004; Fig. 5) were observed. The vertical height at which the unsuccessful attempts stopped was significantly lower than that of the vertical height at T Vmin in successful attempts (Fig. 4). No other significant differences in velocities and height and joint angles at different positions between successful and unsuccessful attempts were found (Figs. 4 and 5).
In both the successful and the unsuccessful attempts, the moment arm about the elbow increased significantly from T Vdown event to T 0. From T 0 to T Vmax, the moment arm only decreased in successful attempts. In unsuccessful attempts, the moment arm only decreased significantly between T 0 and the point of failure. Thus, a significant difference in moment arm about the elbow was found between successful and unsuccessful attempts at T Vmin (Fig. 6). The moment arm about the shoulder did not change significantly during bench press (Figs. 2 and 6).
A significant difference was found in the timing of the maximal downward velocity of the barbell (Table 1 and Fig. 2). No other significant differences in the timing of the different events between successful and unsuccessful attempts were found. The sticking period started and ended at the same time for both attempts (Fig. 2).
For the biceps and the deltoid muscles in both successful and unsuccessful attempts, a significant change in activity during the four periods was observed. The biceps showed decreasing muscle activity during the bench press effort for both attempts. The deltoid showed an opposite, increasing activity pattern (Fig. 7). Moreover, an interaction effect was observed for the deltoid activity (P = 0.004), indicating that activity increased more in the successful attempts compared with that in the failure attempts. Overall, the triceps activity was not affected by period or attempt; nevertheless, an interaction effect was found (P = 0.05). This effect was in the change from the eccentric to the concentric (presticking) period in successful attempts: in a successful attempt, triceps activity during the eccentric phase was significantly lower in the successful attempt than that in the failed attempt (P = 0.004), developing to equal levels during the concentric period (Fig. 7).
The following additional differences were found in comparing successful and failed attempts at specific moments concerning muscle activity. Biceps activity in the eccentric period of the bench press movement was higher in the successful attempts (P = 0.006). The deltoid muscle activity during the presticking period in unsuccessful attempts was also higher in successful attempts (P = 0.003).
In this study, the differences in kinematics and muscle activity between successful and unsuccessful attempts in bench pressing were examined. Failure occurs not only in the sticking period but also after it. Significant differences in kinematics and muscle activity were found between the successful and the unsuccessful attempts.
Only five subjects stopped with lifting during the sticking period. The other six subjects continued lifting after reaching T Vmin and had to give up later. Thus, the sticking period is not necessarily the failure period during the lift. In both the successful and the unsuccessful attempts, the maximal velocity (0.2 and 0.15 s, respectively) and the T Vmin (1.07 and 1.00 s, respectively) take place at approximately the same time (Table 1). Lander et al. (5) found that the sticking period also started after 0.2 s in the ascending phase of bench pressing. Elliott et al. (3) and Wilson et al. (12) found that the sticking period ends at around 1 s after the initial upward movement in maximal bench pressing for both successful attempts at 100% of 1RM and unsuccessful attempts at 104% of 1RM. They also found that several subjects continued lifting after the sticking period, which also occurred in the current study. Thus, the sticking period was of the same length of time in both studies. Both successful and unsuccessful attempts showed increased muscle activity of the deltoid during the upward movement (Fig. 7), which is suggested to be a compensation for the diminishing muscle potentiation after the eccentric phase (10). It should be noted that the absolute EMG-time profiles might be affected by a considerable change of muscle bulk that is located directly under the surface EMG electrodes during the upward movement. The comparison of the eccentric (downward) period and overall concentric (upward) period is unlikely to have been affected; nevertheless, it still shows large differences for both biceps and deltoid muscles. This strengthens the notion that our findings give a reasonable qualitative description of the development of muscle activity during the bench press.
Elliott et al. (3) found that the location of failure in 104% of 1RM attempts corresponded to the sticking periods of 100% load. In the current study, the vertical location of the barbell at which failure occurred was lower than the vertical height of T Vmin of the successful attempts (Fig. 4). This outcome was also evident in the larger moment arm about the elbow joint at T Vmin of unsuccessful attempts. These findings could indicate that the sticking period is a region in which a poor mechanical force position occurs (3). Elliott et al. (3) found that the resultant moment arm about the shoulder joint decreased during the sticking period in both successful and unsuccessful attempts. In our study, the moment arm about the shoulder joint did not change during the different periods. However, the moment arm about the elbow joint in successful attempts decreased significantly by 8% during the sticking period, whereas in unsuccessful attempts, the moments did not change (Fig. 6). This difference can be ascribed to the different vertical heights of the barbell between the attempts at T Vmin (Fig. 4) and thereby the occurrence of a different horizontal shoulder adduction and elbow flexion angle (Fig. 5). The consequence is a higher external moment on the elbow joint in unsuccessful attempts at T Vmin when compared with the moment arm at that point in successful attempts, and thus a poor mechanical force position in which the attempt will fail. One possible explanation for this outcome is that when the subject notices that it is difficult to lift the barbell, he tries to reduce the moment arm on the elbow by moving the barbell in the horizontal plane, closer to the shoulder axis (Fig. 4). However, the vertical height from the chest may not be high enough to get out of the poor mechanical force position and the attempt fails.
It was also hypothesized that muscle activity would be the same or higher because of the increased load between the two attempts. An increase in muscle activity was shown during the downward movement. During the downward movement, the timing, not size, of maximal downward velocity was different between the two attempts. In unsuccessful attempts, this event occurred closer to T 0, the time of lowest barbell point (Table 1), so that the vertical displacement at that point was larger in unsuccessful attempts (Figs. 2 and 4). Thus, the braking period of the downward movement is shorter in the unsuccessful attempts. This means that the muscle activity had to be higher to stop in time the greater mass before it hits the chest during this eccentric phase. This was found for the triceps and biceps muscles that showed a higher activity during the unsuccessful attempts when compared with the successful attempts (Fig. 7).
In the upward movement, muscle activity was not higher for unsuccessful attempts. The deltoid muscle activity was even less in the presticking period when compared with the successful attempts (Fig. 7). Following the rationale of van den Tillaar and Ettema (10), muscle activity needs to increase because of diminishing muscle force capacity (as a result of the fading effects of the eccentric part of the action), which leads to a sticking period. Related to this, the force profile during the bench press dictates the length change of the series elastic element in muscle and accompanying release of stored elastic energy. The contractile and series elastic elements of muscle interact in a rather complex manner. Given a certain joint movement velocity, the shortening of elastic components allows the contractile machinery to shorten at a relative low velocity and thereby generate higher forces. To allow this to happen, the muscle force must decrease during the movement. During the sticking period, the force on the barbell decreased in accordance with the deceleration profile (Fig. 2). Almost by definition, the large acceleration and deceleration occur in the presticking period. During the sticking period, a relatively low and relatively constant deceleration takes place, which means that a relatively constant force, below barbell weight, is produced. If one assumes that muscle forces roughly follow the same pattern, the main release of elastic energy occurs during the presticking period, whereas this release is relatively small during the sticking period. Thus, the (lack of) release of elastic energy seems in accordance with the appearance of the sticking period in which the contractile machinery is at a disadvantage because it has to do all the work and cannot rely on the series elastic component doing part of the work. The major difference between the successful and unsuccessful attempts concerning this issue seems to happen only in the second half of the sticking period. Yet, in the failed attempts, this does not necessarily lead to failure during this sticking period. Because, in the failed attempts, the mass was increased and the muscle activity was the same, the acceleration and peak velocity must have decreased (Table 1). This decreased peak acceleration and peak velocity resulted in the subjects not being able to lift the barbell through the poor mechanical force region as indicated by the different external moment arm on the elbow (Fig. 6). The subjects literally were "stuck" in this region (Figs. 4 and 6). However, total failure apparently often happens after new acceleration, i.e., after the sticking period. The reason that failure still occurs, for example, may be that fatigue sets in strongly or that the hypothesized diminishing effect of stretch contraction plays an important role (10).
The present study was conducted with subjects who were involved in weight lifting and bench pressing at a recreational level. The major findings agree well with those of Elliott et al. (3), who used elite weight lifting athletes. Therefore, we are inclined to conclude that the current findings and conclusions may also apply to higher levels of performance.
The sticking period occurs in both successful and unsuccessful attempts in maximal bench press in recreational weight-trained subjects. However, failure does not always occur during the sticking period; only half of the failures occurred during that period.
This study was conducted without any funding from companies or manufacturers or outside organizations. The results of the present study do not constitute endorsement by ACSM.
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Keywords:©2009The American College of Sports Medicine
EMG; ANGLES; FAILURE; UPPER BODY STRENGTH