Comparison of Chain and Plate Loaded Bench Press by MLB Pitching

COMPARISON OF CHAIN- AND PLATE-LOADED BENCH PRESS TRAINING ON STRENGTH, JOINT PAIN, AND MUSCLE SORENESS IN DIVISION II BASEBALL PLAYERS KEVIN MCCURDY,1 GEORGE LANGFORD,2 JAMES ERNEST,2 DAVID JENKERSON,2 2 AND MICHAEL DOSCHER 1

Department of Health Physical Education and Recreation, Texas State University, San Marcos, Texas; and 2Department of Kinesiology and Physical Education, Valdosta State University, Valdosta, Georgia

ABSTRACT McCurdy, K, Langford, G, Ernest, J, Jenkerson, D, and Doscher, M. Comparison of chain- and plate-loaded bench press training on strength, joint pain, and muscle soreness in Division II baseball players. J Strength Cond Res 23(1): 187–-195, 2009—The purpose of this study was to investigate the effects of chain- (CBP) and plate-loaded (PBP) bench press training on measures of strength, shoulder pain, and muscle soreness in Division II baseball players. Twenty-eight subjects with previous resistance training experience (4.8 6 2.7 years) completed the study while participating in off-season baseball practice. All subjects completed a one-repetition maximum preand posttest on the CBP and PBP and reported shoulder pain and muscle soreness on 15 occasions during training. Two treatment groups, CBP and PBP, trained 2 d wk21 for 9 weeks during the off-season with a linear periodization strength training program. The CBP group used chains attached to the bar as the entire load, and the PBP group used only traditional plate-loaded resistance. The chains provided a variable resistance, with a reduction in load during the descent as the weight collected on the floor and with the load increasing during ascent as the weight was lifted from the floor. Statistically significant increases were found in strength scores after training for the CBP test (p , 0.001) and the PBP test (p , 0.001). Both groups were able to improve strength on the CBP and PBP, but no significant differences were found in strength gains between the groups on the CBP and PBP tests. Although levels of pain and soreness were not significantly different, a threefold difference was found for perceived levels of shoulder pain (mean totals of 2.15 vs. 6.14), whereas

Address correspondence to Kevin McCurdy, km55@txstate.edu. 23(1)/187–195 Journal of Strength and Conditioning Research Ó 2009 National Strength and Conditioning Association

reported soreness was similar (9.38 vs. 10.57) for the CBP and PBP group, respectively. The data indicate that training with chain- and plate-loaded resistance produce similar short-term strength improvement on the chain- and plate-loaded bench press. Baseball players may benefit from CBP training with improved free-weight strength while minimizing shoulder stress.

KEY WORDS shoulder pain, 1RM bench press, variable resistance, dynamic constant external resistance

INTRODUCTION

ree-weight dynamic constant external resistance is the most common type of strength training used for athletic conditioning. An advantage of freeweight training is the requirement to stabilize the unsupported resistance. The unstable load provides a neuromuscular stimulus for strength improvement that is widely accepted to be most specific to forces required for improved athletic performance. However, because of evidence that constant external resistance may not provide optimal resistance through the complete range of motion during most exercises (26,31), the use of chain-loaded resistance has been used to provide a variable free-weight resistance that may enhance strength gains above those achieved by traditional free weights (35). Chains can be combined with plate-loaded resistance or added to the bar as the entire load. The chains hang from the bar with the bottom links resting on the floor (Figure 1). As the bar is lowered to the chest, more links collect to the floor, reducing the load (Figure 2). The load increases as the chains are lifted from the floor. Although these innovative methods are increasingly used, no known research studies have been conducted to determine strength gains after training with chain-loaded resistance. Several studies have shown that the bar decelerates during ascent using dynamic constant external resistance for a significant portion of the bench press (19,31). Reduced force and power have also been reported during this period of bar deceleration. Lander et al. (26) report that the force VOLUME 23 | NUMBER 1 | JANUARY 2009 |

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Figure1. Top position of the chain-loaded bench press.

produced during the bench press was less than the weight of the bar in the sticking region and near the end of the motion. Further, if plate-loaded resistance cannot be lifted past the position at which the body produces the least amount of force, overload cannot take place near the top of the bench, where the body is capable of producing higher forces. The bench press is an ascending strength curve exercise, with the mechanical advantage of the body increasing as the bar is lifted off the chest (3), and, as a result, plate-loaded resistance may not offer optimum loading during the complete range of the exercise. Chain-loaded resistance may better match the bodyâ&#x20AC;&#x2122;s strength curve by providing less resistance at the bottom of the lift when the body is in the greatest disadvantage to produce force during the bench press. Near

Figure 2. Bottom position of chain-loaded bench press.

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the top position, the resistance increases while the bodyâ&#x20AC;&#x2122;s mechanical advantage increases. Reduction of the load at the bottom of the chain-loaded bench press may not provide adequate overload to induce strength improvement within this range of motion during maximum strength assessment with dynamic constant external resistance (36). The principle of specificity suggests that the greatest strength gains occur when testing and training modes are similar. Strength gains from chain- and plate-loaded resistance training may not transfer to strength improvement on the free-weight test not used in training. For example, training with chain-loaded resistance may not evoke an adequate training adaptation to produce the necessary force during the eccentric and concentric contractions of a plate-loaded resistance test with the bar near the bottom position. Conversely, plate-loaded training may not produce improved strength required to overcome the increasing force presented by chains near the top of the lift. These possible results would demonstrate limitations of each type of bench press training to increase maximum strength during a specific range of motion of the bench press not used during training. Enhanced strength with chain-loaded resistance has been speculated to occur from an improved rate of force development because of lifting lighter loads near the bottom of the bench press, resulting in greater bar acceleration (35). The improved strength may also occur from enhanced coordination of agonist and synergist muscle groups to control the chain-loaded resistance. Chain-loaded resistance seems to provide a slightly more unstable resistance than plate-loaded resistance because of the movement of chains during the loading and unloading from the floor. Behm and Anderson (6) conclude that slightly reducing the stability of the resistance may provide optimum stress on the neuromuscular system for maximum strength improvement. Highly unstable loads significantly reduce force production and may not induce sufficient overload required for strength gains (7). Bench press training with chains may produce improved strength and shoulder stabilization by providing an appropriate level of instability. Prevention of athletic injury is another important role of the strength and conditioning program. Shoulder injuries are the most common type of injury for baseball players (30). Lachowetz et al. (25) found that baseball players who participated in a short-term strength training program had less shoulder pain than a control group at 24, 48, and 72 hours after a throwing session. Pain levels were not recorded throughout the training after each training session, which may produce higher stress on the shoulder than is perceived to occur after a throwing session. Several authors have reported that the traditional bench press exercise places stress on the anterior capsule, ligaments, and tendon structures of the glenohumeral joint with the resistance near the chest (17,34,37). Traditional high-intensity bench press training to improve strength may increase the risk of

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Journal of Strength and Conditioning Research shoulder injuries in baseball players who participate in baseball practice because of the repetitive stress involved during throwing and strength training. Currently, no known studies have been conducted to monitor the degree of shoulder pain during the course of a strength training period in highly skilled baseball players who concurrently participate in throwing practice. While providing a reduced load with the bar near the chest, the chain-loaded bench press seems to minimize shoulder stress. Thus, chain-loaded resistance may be best suited for baseball players who want to gain upper-body, multijoint strength while minimizing joint stress and the risk of injury. Research is needed to determine the training effects of chain-loaded resistance in highly skilled athletes. Although traditional free-weight bench press is an exercise known to increase strength, innovative variable free-weight resistance equipment is being used by athletes to compensate for the limitations that may exist with this type of training. Limited data are available to determine the most appropriate type of resistance training that should be used by highly skilled baseball players to improve strength and minimize the risk of injury. Therefore, the purpose of this study was to compare strength gains, shoulder pain, and muscle soreness after plate- and chain-loaded resistance training in Division II baseball players.

METHODS Experimental Approach to the Problem

Baseball players were selected as subjects to investigate the effects of bench press training with different modes on strength gains and shoulder stress. With a high incidence of shoulder injury, baseball players could benefit from a resistance training program that improves upper-body strength to improve performance while minimizing shoulder stress. The subjects were separated into two groups, chain-loaded resistance (CR) and plate-loaded resistance (PR). The CR group used only chains, whereas the PR group used only plates as the entire load added to the bar to better determine the effects and limitations of each type of training. Both groups also trained with free weights, bands, and cables to provide an appropriate upper-body resistance training program for baseball players. Although the combination of chains and plates has been used as a training method, training with chains as the entire load presents a greater reduction in the resistance between the top and bottom positions of the bench press and, consequently, the greater potential to reduce shoulder stress during training. To determine the difference in joint stress and muscle overload between the groups, the subjects reported perceived shoulder stress and muscle soreness experienced immediately after and between training sessions, respectively. To determine exercise intensity and monitor strength gains, all subjects completed a chain- and plate-loaded onerepetition maximum (1RM) test during a pre- and posttest. The relative training intensity was the same for each group.

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Training load was determined for the CR by using a percentage of the subject’s 1RM on the chain-loaded test, and the load for the PR group was based on the subject’s plate-loaded 1RM. A chain- and plate-loaded linear periodization program was implemented to determine whether these modes used to improve bench press strength produced differences in perceived shoulder pain. The specificity of training was investigated by testing all subjects on the chainand plate-loaded bench press to determine the ability to transfer strength gains to a test not used during training. Although both groups trained with free-weight resistance with equal relative intensity, the differences in the load (variable resistance vs. dynamic constant external resistance) experienced at different positions in the range of motion may affect the ability improve strength on the mode not used during training. Subjects

Twenty-seven Division II baseball players completed this study. Both starters and nonstarters who completed a winning season were included as subjects. The subjects’ mean age, height, and weight were 20.63 6 1.33 years, 178.89 6 5.46 cm, 84.79 6 5.84 kg, respectively. All of the subjects signed written informed consent forms that were reviewed by the institutional review board at the university to ensure that the subjects were knowledgeable of the normal risks and procedures involved in the study. All subjects had a minimum of 1 year of resistance training experience (mean of 4.82 6 2.74 years) that included plate-loaded resistance training, but they did not have training experience with chain-loaded resistance before this study. All but four of the subjects participated in 1–3 years of year-round resistance training experience in the same program. Before the study, the subjects typically trained in the off-season with a program similar to the training used in this study (Table 1). This study took place during the off-season while the subjects participated in baseball practice, 3–4 d wk21. One-Repetition Maximum Test Procedures

Two sessions were devoted to practicing the chain-loaded bench press (CBP) and plate-loaded bench press (PBP) techniques with light to moderate loads that approached the subjects’ estimated 1RM values and measuring the distance from the bar held in the top position of the bench press to the floor. Seven-foot chains varying in size from 1- to ¼-inch links were used to add resistance (Figure 1). Each chain was labeled with a different color for the purpose of identifying the correct size of chain and weight resistance. The length of the chains lifted off of the floor in the top position for each subject’s top position was weighed to determine the load added to the bar. By varying the combinations of the different chains, resistance could be added in approximately 5-lb increments. The chains hung from collared hooks that were secured to the bar. To improve stabilization, a portion of the chains remained in contact with the floor. High test-retest reliability has previously been found on the CBP (27). VOLUME 23 | NUMBER 1 | JANUARY 2009 |

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TABLE 1. Training program. Week

Exercise

Sets

Reps

% 1RM

Bench Dumbbell pronation/supination Tubing circuit Barbell bent rows Anterior/lateral/rear dumbbell raise Bench Repeat assistance exercises Added wrist curls/radial and ulnar deviation Bench Repeat assistance exercises Add grip exercise (holding 5-lb plates) Add one set to tubing and reduce rows to eight reps Bench Repeat assistance but replace bent rows and with cable rows and medicine ball circuit for tubing circuit Bench Repeat assistance exercises Bench Repeat assistance exercises Replace shoulder raises with alphabets (write alphabet with 5-lb plate held anterior and shoulder height) Bench Repeat assistance Replace cable rows with bent rows (add one set) Bench Repeat assistance Replace plate holds with rope pull-ups Bench Repeat assistance

5 2 1 3 4 5

5 2 1 3 4 8

2 5

10 7

1, 1, 6

6, 5, 4

70, 75, 80

1, 1, 6

5, 4, 3

75, 80, 85

1, 1, 6

5, 3, 2

80, 85, 90

1, 1, 7

3, 2, 1

75, 85, 95

1, 1, 3

8, 6, 5

60, 65, 70

2 3

4 5 6

7 8 9

65 70

Percentages for the chain-loaded resistance (CR) group were based on their chain-loaded bench press (CBP) one-repetition maximum, whereas the plate-loaded resistance (PR) groups trained at the same percentage based on their plate-loaded bench press (PBP) 1RM. Program shows the heavy day while training percentage was reduced 5%–10% with a slight increase or equal volume on the lighter day. Tubing and medicine ball circuit included shoulder internal/external rotation and abduction and adduction. All assistance exercises were performed with maximum weight possible to complete the required repetitions.

The subjects were instructed to take a grip width slightly wider than the shoulders and to lightly touch the chest before returning to the top position while keeping the feet on the floor and the hips and head on the bench. All subjects from both groups completed the PBP 1RM test, followed by the test on the CBP, with a minimum of 4 days of rest between each test. A 5-minute warm-up and upper-body stretches were monitored before each test. All test procedures were monitored by the investigators and were provided in clear view for the subjects to read. Before the CBP test, trial loads were calculated to determine the combination of chains that increased the loads in 5% increments from an initial trial of 105% to a possible final trial of 150% of each subject’s PBP 1RM. These percentages were used because the subjects were able to lift more weight in the CBP test. During the CBP tests, the color of the chain was called out to load the required weight. After two warm-up sets of five repetitions using light loads, a moderate weight was

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added to complete two to three repetitions. A 2- to 4-minute rest period was allowed before increasing the resistance by 10–20% for the initial 1RM trial. Two to three minutes of rest were allowed on each successive 1RM trial after adding 5– 10% of weight, depending on the ease of the successful lift. If the subject was unsuccessful, 2.5–5% was subtracted for a final set (4). After training, a posttest on the CBP and PBP took place 3 days after the final training session. Shoulder Pain and Muscle Soreness Measurements

Each subject was measured 15 times throughout the training regimen on two measures: pain and soreness. The 15 measures for pain and 15 for soreness were totaled and divided by each group’s sample size to calculate a mean of the total scores. Before each training session, the subjects were asked to report their level of upper-body muscle soreness experienced during the period after the last training session. The subjects reported the level of shoulder pain experienced

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Journal of Strength and Conditioning Research during the session immediately after each training session. For shoulder pain, the subjects were instructed to determine the level of pain within the joint. The difference between joint pain and muscle soreness was described to the subjects to ensure that the subjects were able to differentiate between these variables. The subjects were instructed to rate the perception of pain and soreness using the following category scale: 0 = no pain, 1 = mild pain, 2 = moderate pain, 3 = severe pain, and 4 = worst pain possible. Similar category scales with ratio data properties have been used to measure the perception of pain (23,29) and have been tested for reliability and validity by correlating concurrent pain scores with standard 10-cm visual analogue scales (11,12), which have the same verbal anchors used in this study. These data were statistically analyzed to provide a comparison between the groups using the overall reported indication of soreness and pain during the training period. To analyze the effects of the training on soreness and pain over time, the 15 data points were divided into five scores at the beginning, middle, and end of training. The five measures for pain and soreness were totaled and divided by the sample size of each group to calculate a mean for each group. Training

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week. In addition to the bench press, each training group completed the following exercises: plate-loaded bent rows, cable rows, dumbbell forearm pronation/supination, barbell wrist curls, rotator cuff tubing and medicine ball circuit with internal/external rotation and abduction/adduction, dumbbell anterior/lateral/rear rows, rope pull-ups, grip exercises, and shoulder alphabets (Table 1). Statistical Analyses

Differences in pretest strength scores were determined using an independent t-test. Multivariate repeated-measures analyses of variance of the data were used to analyze the main and interaction effects for training regimen and time. Followup univariate analyses of variance were used to analyze the difference in strength, pain, and soreness scores over time by group. An alpha level of 0.05 was set for all statistical tests.

RESULTS No significant differences were found between training groups for 1RM on the PBP (p = 0.98) and CBP (p = 0.80). Strength descriptive data for pre- and posttest measures are reported in Table 2. Multivariate repeated-measures analyses of variance of the data found no interaction effects between training regimen and time. Univariate analyses found statistically significant increases in strength scores over time for the CBP group (p , 0.001, partial h2 = 0.67) and the PBP group (p , 0.001, partial h2 = 0.63). A repeated-measures multivariate analysis of variance indicated a statistically significant effect over time for pain (Wilks l p = 0.005, h2 = 0.48) and no interaction for pain recorded across 15 scores (mean totals of 2.15 vs. 6.14) or soreness (9.38 vs. 10.57) between the CBP and PBP groups, respectively (Wilks l p = 0.17). The within-subjects contrast of time indicated a quadratic effect for soreness, with participants indicating a decrease in soreness from the beginning to the middle of their training, then increasing soreness from the middle to the end (p , 0.001, h2 = 0.42) (Figure 3). The results in Figure 3 reveal a greater degree of pain for the subjects who trained on the PBP compared with those who trained on the CBP (p = 0.068, h2 = 0.13). The low

After completion of the pretests, the subjects were divided into either a CR or PR group on the basis of pretest strength to ensure that the groups had similar strength levels before training. The subjects trained for 9 weeks, 2 days each week, and this training was monitored by the investigators. During the study, the subjects were instructed to refrain from training with any type of bench press movement other than the training protocol provided in this study. Before each training session, the subjects performed a general and sport-specific warm-up and upper-body stretches. A linear periodization resistance training program was implemented. A heavy and light day were implemented each week, with the heavy day reported in Table 1. On light days, the percentage was reduced 5â&#x20AC;&#x201C;10% on each set; the volume was either higher or remained the same as on the heavy day. To make the relative intensity equal for each group, the subjects in the CR group trained at a percentage of the CBP 1RM, whereas the PR group trained at the same percentage based on their PBP TABLE 2. One-repetition maximum pretest and posttest. 1RM. Initial percentages were Chain-loaded training determined to be appropriate Variable group (lb), mean 6 SD for building a foundation of strength while preventing overPlate-loaded bench press training. The volume decreased Pretest 225.55 6 36.38 with an increase in training Posttest 238.57 6 21.96 Chain-loaded bench press percentage during the 9 weeks, Pretest 334.06 6 59.67 with near-maximum percenPosttest 383.38 6 29.64 tages used in the final weeks. The ninth week was included as a maintenance and recovery

Plate-loaded training group (lb), mean 6 SD 225.83 6 31.73 240.00 6 28.55 338.89 6 53.62 364.07 6 50.24

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Figure 3. Shoulder pain and muscle soreness data.

power (p = 0.12) indicates that significance would be found with a larger sample.

DISCUSSION Training with CBP and PBP produces similar strength gains using the plate- or chain-loaded resistance mode of testing. Previous research has supported the principle of specificity, with findings demonstrating that the greatest gains are achieved when subjects are tested under similar conditions used during training (13,20). The data in this study do not refute the principle of specificity, because both groups trained with free weights. However, this research shows that similar strength improvement can occur on a free-weight mode not used in training in resistance trained athletes who train with variable or constant free-weight resistance using the same relative intensity. Both groups demonstrated similar gains on the plate-loaded test, but the CR group increased 24 lb above the improvement demonstrated by the PR group on the chain-loaded test. Although not statistically significant (p = 0.24), these data may indicate a limitation of plate-loaded training to improve strength near the end range of the bench press. The PR and CR groupsâ&#x20AC;&#x2122; training percentages were based on their PBP and CBP 1RM, respectively. Using chains as the entire load may significantly reduce the resistance near the bottom range of the bench press and,

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arguably, may not provide a sufficient load to increase strength on the PBP. The data in this study indicate that, when using the same relative intensity based on the CBP 1RM, a sufficient load is used at the bottom of the lift to produce increased PBP strength. The subjectsâ&#x20AC;&#x2122; CBP strength was approximately 34% higher than their PBP 1RM. Although there is an approximately 40% difference in bar height from the top to the bottom position depending on arm length and chest thickness, actual differences in load are slightly less than 40% when accounting for the constant load of the 45-lb bar. The relative loads near the bottom range for the CR group were slightly lower than the PR loads because of the difference in bar height from the top to the bottom position and the accumulation of the chains stacking on top of each other on the floor. A greater portion of the chain is unloaded with stacking for a given bar height from the floor. Stacking of the chains can be partially controlled by aligning the end of the chains parallel to the bench (Figure 1). With several chains required to provide the necessary load, preventing stacking of the chains cannot be completely accomplished. Higher bar velocities likely occur with the reduced relative loads near the bottom range of the exercise, which may assist the subject in lifting higher relative loads near the end range of the movement. Neuromuscular adaptations related to improved bar acceleration in the early

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Journal of Strength and Conditioning Research range of the bench press with the use of combined plate- and chain-loaded resistance is suggested to maximize strength improvement (35). When using the percentage of the CBP 1RM, higher loads are encountered at the top of the lift during the CBP compared with the load experienced by the PR at the same relative intensity. This increased load may provide optimum loading as the body’s force capability increases near the top position of the bench press. Furthermore, the CR groups’ strength gains found on the PBP test may have occurred because of the intention to move the bar at the greatest velocity, which compensated for the reduced load lifted through the initial ascent during the CBP. Behm and Sale (9) previously have concluded that a principal factor that affects velocity-specific strength adaptations and power improvement is the intention to maximize bar velocity regardless of the actual velocity. Using this lifting technique, strength gains may have been attributed to some extent from neural adaptations suggested to occur by Behm (5). Subjects in the CR group may have used this technique to lift the chain resistance through the complete range of motion to overcome the increasing load near the top of the lift without fear of injury caused by completing extension of the elbow. Newton et al. (33) have suggested that variable resistance, applying an increasing load through the range of motion, naturally breaks the movement and decelerates the load, allowing continuation of force production near the top of the lift. Elliot et al. (19) have shown that bar velocity decelerates 51% of the concentric movement time when using 81% of the 1RM with reduced force output near the lock-out position of the PBP; thus, Newton et al. (31) have proposed the use of ballistic exercises to atone for this limitation of traditional dynamic constant external resistance training. Similar results were reported by Lander et al. (26), who found that force output less than the load lifted (sticking region) occurs for 26% of the time early in the bar’s ascent and for 18% of the time near the end of the PBP. Although the bar decelerates near the end of the CBP as the load increases, higher force production may occur for a longer period through the bench press range of motion with this type of variable resistance. Conflicting evidence exists regarding comparisons between traditional plate-loaded resistance and combined chains or bands with plate-loaded resistance exercises on electromyography, peak force, and power output. Studies that have not found a difference in one or more of these variables (10,14,18) used a relatively small percentage (5–20%) of the load contributed by bands or chains, whereas differences have been shown to be evident using larger percentages (2,33,38). Acute and chronic training effects on force and power are yet to be determined using chains as the entire load. The strength findings of the present study may be further explained by an analysis of the difference in stability between the CBP and PBP. Neuromuscular activation levels leading to improved strength improvement are affected by the amount of stabilization needed to control the resistance (6). Although neuromuscular activation can increase as the load becomes

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more unstable (8), force production is significantly reduced during highly unstable resistance exercises (1,24). Overload tension on the muscle is suggested to be vital to maximize strength training adaptations (5,36); therefore, an optimum level of required stability may be essential to produce maximum strength improvement. Chains seem to be a slightly more unstable free-weight resistance than plate-loaded resistance. The unstable resistance is created from the stacking and unstacking of the chains on the floor. This instability may induce an optimum stimulus for strength improvement. Further research is needed to compare strength improvement using different types of free-weight equipment that require differences in stabilization to control the resistance. Few studies have analyzed shoulder pain in highly trained baseball players during the in- or off-season. Lachowetz et al. (25) report that shoulder pain was lower during a 3-day period after throwing practice in intercollegiate baseball players who participated in an 8-week strength and conditioning program compared with a control group that did not perform resistance training. The program consisted of the free-weight bench press along with several exercises that were performed using Nautilus, Cybex, and cable pulley system equipment. The authors found low levels of pain after the throwing session, and they conclude that the intensity of the throwing session may have been insufficient to determine group differences. In contrast, shoulder pain was previously reported as a reason to refrain from resistance training in a group of trained weight lifters (21). Therefore, shoulder pain in this study was recorded to determine the levels experienced after each training session, and muscle soreness was reported according to the levels perceived between training sessions. The results indicate that similar strength gains and muscle soreness can occur with CBP and PBP training while experiencing reduced levels of shoulder pain with CBP training. With year-round participation in baseball and strength/ conditioning training, it is imperative that the exercises used during training provide neuromuscular adaptations with minimum joint stress and risk of injury. The shoulder joint is the most common joint injured in baseball players (22,28). Although strength training has been shown to increase strength and throwing velocity in baseball players (32,39), some players do not train using the bench press because of pain experienced during the exercise or because of speculation that this exercise places high stress on the shoulder (17,34,37). The anterior glenohumeral tissue is the most common site for joint hyperlaxity and instability (16) and receives the greatest stress during the bottom position of the bench press (17). Throwing athletes are at a high risk for shoulder injury because of the repetitive stress placed on this site during shoulder external rotation, abduction, and horizontal abduction during the throwing motion and also during bench press training, which can exacerbate anterior shoulder instability and lead to shoulder impingement (15). The data in this study indicate that the decreasing load as the VOLUME 23 | NUMBER 1 | JANUARY 2009 |

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Chain-Loaded Bench Press CBP bar nears the chest produces lower levels of shoulder stress, which are reflected by the lower perceived level of pain in the CR group. With lower perceived levels of shoulder pain, subjects are more likely to perform the exercise with higher intensity and effort, producing improved strength regardless of the potential differences in loads occurring through the range of motion between the CBP and PBP. Although not statistically different, perceived shoulder pain was approximately three times lower in the CR group. Pain data were recorded 15 times across the 9 weeks of training and were divided into 3-week periods to analyze differences in the beginning, middle, and end of the training. From a clinical analysis of the data, a larger percentage of the PR subjects reported some level of pain during the beginning (43 vs. 14%), middle (36 vs. 14%), and end (43 vs. 36%) of the training period. Moderate levels of pain were reported once for two subjects in the CR group, whereas eight subjects in the PR group recorded moderate levels of pain for a total of 16 times, with two subjects in this group recording a severe level of pain once that prevented them from completing the training session. Although the average pain levels seem to be low for both groups, reports of low levels of pain (1 = mild or 2 = moderate) for elite players at any phase of training require attention to determine the cause and risk of injury.

PRACTICAL APPLICATIONS The results of this study indicate that chain-loaded resistance can be used as the entire load to the bar to produce similar strength gains from training with plate-loaded resistance while experiencing reduced levels of shoulder pain. Reduced shoulder stress is essential for baseball players who participate in baseball and strength/conditioning year-round. Bench press training with free-weight resistance is considered a primary exercise to develop multijoint, upper-body strength. Increased upper-body strength has also been determined to improve throwing and hitting performance. Despite these positive effects, strength training on the bench press is sometimes not included for baseball players, to minimize the risk of shoulder stress and injury. With chain resistance, baseball players and other athletes who are at high risk for shoulder injury may be able to increase their training emphasis on strength improvement, with less risk for shoulder stress induced by participation in sport or training. Although chains can be combined with plate-loaded resistance, using chains as the entire load provides a greater reduction in load from the top to the bottom position of the bench press and, subsequently, a greater stress reduction in the shoulder. Although bench press training is important to build foundational upper-body strength, the effect of maximizing strength potential on improved throw performance is yet to be determined. Resistance training emphasis should also be placed on improving concentric and eccentric shoulder rotational forces and muscle balance involved in stabilization of the shoulder complex.

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The strength gains found in this study occurred after training at similar relative intensities. The CR training percentages were based on that group’s CBP 1RM, whereas the same relative load for the PR group was based on their PBP 1RM. As a result of higher 1RM scores produced on the CBP test calculated from the load held in the top position, higher loads were encountered near the top position and lower loads near the bottom range during CBP training. With this method of chain-loaded resistance, bar velocities produced during training were likely slightly faster near the bottom range and slower near the top range than velocities produced during PBP training. The effects that these differences in load and bar velocity have on power and sport performance are yet to be investigated.

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