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Original Research

10-Year Changes in Upper Body Strength and Power in Elite Professional Rugby League Players—The Effect of Training Age, Stage, and Content

Baker, Daniel G.

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Journal of Strength and Conditioning Research: February 2013 - Volume 27 - Issue 2 - p 285–292
doi: 10.1519/JSC.0b013e318270fc6b
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Abstract

Introduction

It has been theorized that considerable gaps exist in our understanding of the long-term adaptations to resistance training because of the short-term nature of most university-based training studies (46,47). Much of the literature concerning resistance training adaptations is based on short training studies of 6–12 weeks consisting mainly of college students with limited resistance training experience serving as subjects (21). It has been demonstrated that the effectiveness of one program over another program may take at least 8 weeks to manifest itself (26,27,30,31,36). How the adaptations stemming from these shorter training studies reflect the adaptations that athletes training for many years experience has been questioned by both experienced strength coaches and researchers alike (46,47).

Most of these short-term studies illustrate the relative ease with which strength may be increased in novices and those with a more limited training history (26,27,30). Conversely, empirical experience and the few long-term studies that have been done to date also illustrate the great difficulty that exists in trying to increase strength in experienced elite strength-power athletes (2,6,9,13,16,32,33). Currently, most of the knowledge of long-term resistance training adaptations in elite athletes tends to rely on cross-sectional data analysis (28,29) and empirical training observations. Very little longitudinal tracking data exist concerning the extent and nature of muscular and strength-power adaptations resulting from prolonged resistance training over a multi-year period in elite athletes. Only a few studies exist that track changes in maximal strength, force, power, or various other muscular functioning tests across multi-year periods in advanced athletes. These studies have included the tracking of weightlifters across 2 years (32,33), women collegiate gymnasts across 3 years (24), and collegiate basketball players across 4 years (35). More recently changes in both upper and lower body strength and power across 2 years (2), upper body strength and power across 4-year (13) and 6-year periods (9), and lower body strength and power across 4-year periods (16) have been reported in professional rugby league and union players. All of these long-term studies have not only reflected that changes in muscular functioning reflect the nature of training but also suggested decreasing levels of improvement with increased training experience. Thus to date, the longest study period concerning resistance training adaptations in athletes has been 6 years. Given the diminishing scope for improvement in strength and even more so in power output that was evident in the 2 studies that looked at elite athletes (9,33), the nature of even longer-term adaptations (>4 to 6 years) requires further examination.

In consideration to long-term training phases and adaptations, Balyi et al. (18–20) have identified different stages that athletes progress through in their Long-term Athlete Development (LTAD) model. The last 2 stages, the Training to Compete and Training to Win stages of this model, can differ in the overall objective (as the names suggest), and therefore, the total training content and competition schedule (18–20). Conceivably, the magnitude and nature of strength and power adaptations could differ in these stages of the athletes career because of the differences in training content and competition demands or perhaps even because of the existence of a strength ceiling as proposed by Sale (45).

The purpose of this study is to report the changes in upper body strength and power levels and shifts in the load-power curve for a group of 6 highly resistance-trained professional rugby league players across a 10-year period that encompassed the Training to Compete and Training to Win stages of the LTAD model identified by Balyi et al. (18–20).

Methods

Experimental Approach to the Problem

A number of upper body strength (1996–98, 2000 and 2004–06) and power (1997–98, 2000, 2004–06) testing sessions were conducted across a 10-year period with test data reported according to 2 important training stages in the careers of elite professional rugby league players. The first stage, known as the Training to Compete stage (1996–1998), is associated with an emphasis on enhanced physical development as the athletes in this study attempted to establish themselves as elite professionals in the National Rugby League (NRL) within Australia. The latter Training to Win stage (2000–2006) monitored the changes in strength and power of the players who were now clearly established as elite NRL professionals. This latter stage is characterized by a longer competition schedule and shorter periods devoted to improving physical preparation. In this situation, it is important to consider year 2000 as a pivotal point of the athletes' career and 1996–1998 as typical of Training to Compete and 2004–2006 as Training to Win.

This comparative analysis would provide information pertinent to the long-term changes in strength and power output as a result of intense resistance training across a multi-year period in game-sport athletes as compared with competitive lifter athletes. Importantly, it would illustrate the nature, magnitude, and scope of changes across a professional athletes career as the total training/competition regimen changed.

Subjects

Six professional rugby league players who were experienced in strength and power training served as subjects in this investigation. All subjects were members of the same World Champion club team and underwent similar training (relevant to their playing position and individual strength and power levels) during the 10-year period. The mean (SD) height, body mass, and age of the subjects in 1996 were 186.3 cm (6.8), 95.8 kg (14.6), and 19.3 years (1.6), respectively.

At the start of the observation, the subjects were training with the aim to establish themselves as elite professionals but were participating in second division (or lower) teams. By 1998–1999, all the subjects had become members of the elite professional NRL team, and hence, this observation tracks their strength and power levels throughout 2 distinct phases of their career: the sub-elite development phase (1996–1998/1999) where they are attempting to increase their physical capacities to match elite NRL performers in the sport [known as the Training to Compete Phase (18–20)] and the phase whereby training efforts are directed more toward maintaining these established physical capacities while attempting to perfect the game skills and strategies associated with winning at the highest levels [Training to Win Phase (18–20)]. The Training to Win phase is also associated with greater competition demands (more games per year and accordingly more game-related training) and consequently less time available for physical development training.

Throughout the course of this observation and their entire professional careers, all subjects were subject to stringent independent doping control under the relevant World Anti-Doping Agency authorities (e.g., Australian Sports Doping Agency). Typically, this entailed 3 to 6+ random (24/7/365), out-of-competition, and in-competition drug tests per year.

All subjects were aware of the methods and nature of the testing and voluntarily participated in the testing sessions, which were a regular part of their testing and conditioning regime. All subjects were treated according to the Helsinki Declaration on the rights of human subjects during medical experiments.

Training

The training program has previously been extensively described (4,6,9,13,16). Briefly, the training program was periodized throughout the year with general preparation (usually 4–8 weeks per year), specific preparation (usually 6–10 weeks per year), and in-season competition (usually 24–28 weeks per year) periods in the Training to Compete stage. For the Training to Win stage, both the general and specific preparation usually lasted only 2–4 weeks each per year and in-season competition period usually lasted 27 to 37+ weeks per year.

Training for the upper body was conducted on average twice per week in the preparation phase. The general preparation phase contained only exercises that developed hypertrophy, basic strength, and agonist/antagonist muscle balance. The specific preparation phase contained explosive power development exercises and strengthening exercises.

In-season resistance training followed a wave-like periodization progression (3,4). The wave-like progression has been described previously (4), but briefly it entailed repeating 2 cycles of 3 weeks or 2 cycles of 4 weeks with wave-like progressions in intensity. The first 3- to 4-week block was geared slightly more toward developing basic strength and hypertrophy with a concomitant decreased volume of power exercises, whereas the second 3- to 4-week block was geared slightly more toward peaking maximum strength and power with an increased number of power exercises, increased training intensity, and decreased training volume.

Within each training week, the first training day was oriented slightly more toward the development of maximal strength and the factors that affect strength (e.g., hypertrophy, agonist/antagonist muscle balance), whereas the second training day was oriented slightly more toward the development of power and other factors that affect power (e.g., acceleration, rapid force development, ballistic speed). This alternating of strength- and power-oriented training days also caused an undulatory pattern (a higher load-volume and lower load-volume) in the weekly periodization scheme throughout the year.

In 2004, because of the rule changes within the game, an increase in strength-endurance (S-E) was also pursued. This entailed a reduction in training time devoted to maximal strength, power, and hypertrophy to accommodate the increased volume of higher repetition S-E training. Typically, this S-E training consisted of sets of 20 repetitions with 30–60% 1RM in typical resistance training exercises such as squats, bench press, and pull-downs and a complex of 7 weightlifting style exercises. This “weightlifting” S-E complex typically consisted of 10 repetitions for each of the following exercises: bent rows, high pull from hang, power clean from hang, push press, back squat, power clean from hang, and high pull from hang performed in order nonstop without rest for 2.5–3 minutes till completion. The resistance used was 40–50% of each subjects' 1RM power clean from hang. Heart rate data typically displayed HRs of >92% maximum for 2–3 minutes that this particular weightlifting S-E complex entailed and an average of 85% overall for S-E sessions. The “end of season” periods where no formal training occurred were usually 4–6 weeks per year.

Testing

Testing was performed at the end of preparation period in the first week of March every year, after 2 trial games had been played, but in the week before the in-season fixtures started where there was game scheduled when all subjects were expected to be at peak strength and power levels and were injury free. Specifically, the testing occurred at the end of the training cycle, which was designed such that the athletes would be peaking on the specific day of testing, similar to a powerlifter peaking for a competition. This was done to ensure that the athletes would be at peak strength and power levels for testing each year. Testing was conducted between 9 and 11 AM on each occasion, in the same room and with the same experienced tester used for all tests on all occasions, minimizing the likelihood of inter-test variation that could occur across such a long time period.

Testing consisted of maximum upper body strength as assessed by the 1 repetition maximum bench press (1RM BP) according to the methods previously outlined (5–12,14,16). A test-retest reliability of r = 0.96 in the 1RM BP was previously established with a group of 25 subjects. Testing of upper body maximum power (Pmax) was assessed during bench press throws (BT) using the Plyometric Power System (PPS; Plyopower Technologies, Lismore, Australia) and the methods previously described (10,11,13,14). The measure of mean power output used in this study is assessed for the entire concentric range of movement, as opposed to peak power, which is assessed for the smallest sampling period within a movement.

Bench press throws in a Smith machine weight training device such as the PPS result in much higher power outputs than traditionally performed bench presses making this exercise more suitable for power testing (43,44). Briefly, the PPS is a device whereby the displacement of the barbell is limited to the vertical plane as in a “Smith” weight training machine. The linear bearings that are attached to each end of the barbell allow the barbell to slide up and down 2 hardened steel shafts with a minimum friction. A rotary encoder attached to the machine produced pulses indicating the displacement of the barbell. The number of pulses, denoting barbell displacement, and the time of the barbell movement were measured by a counter timer board installed in the computer. The PPS software calculated the average power output of the concentric phase of each bench press throw based on the displacement, time, and mass data. Specifically, each subject performed 3 repetitions during bench press throws with 40, 50, 60, 70, and 80 kg. The highest mean power output for any individual, irrespective of the resistance, was deemed the 1 repetition maximum bench press and mean maximum power (BT Pmax) (10,13,14). A test-retest reliability of r = 0.92 was previously established with a group of 12 subjects.

Statistical Procedures

Because of the low subject numbers and the elite nature of the subjects, the changes were also analyzed according to the concept of smallest worthwhile change (SWC, 34) and effect size (ES, 23). Briefly, the SWC is a reference value (calculated as 0.2 of the pooled between athlete SD) that permits the calculation of the probability that an observed change in score is large enough to have an important effect on performance in team sport athletes (34). This statistical methodology has been advocated when studying elite athletes who display smaller changes than typical or less trained populations (34) and has been used in previous studies of elite athletes (1,16). These small changes sometimes may not achieve traditional statistical significance despite being possibly worthwhile in the competition environment of the elite athletes. According to Hopkins (34), changes in performance can be categorized as trivial (≤ES × 0.2), small (ES × 0.2–0.6), moderate (ES × 0.6–1.2), large (ES × 1.2–2.0), and very large (ES × >2.0).

Cohen's effect size statistics were also calculated for the magnitude of difference observed between the test scores in different years (23). Effect size differences between the first year of each particular test, which served as the baseline condition, and the following tests were calculated by dividing the difference between the results by the pooled SD of the test results. The ES and SWC were also calculated for year 2000 onwards to determine the magnitude of changes during this latter stage.

Results

The results for changes in 1RM BP strength and BT Pmax are outlined in Tables 1 and 2, respectively. Increases in strength and power were 22.3% (ES of 1.66) and 23% (ES of 1.75) by year 2006 from their baseline figures in 1996 and 1997, respectively. In respect to the different stages of LTAD, the change in strength was 19.3% from 1996 to 2000 (ES of 1.43) and 2.5% from 2000 to 2006 (ES of 0.22). The change in power was 16.6% from 1997 to 2000 (ES of 1.26) and 5.6 % from 2000 to 2006 (ES of 0.49). The mean (SD) body mass increased from 95.8 kg (14.6) in 1996 to 100.0 kg (13.2) in 2000 (ES of 0.30) to 101.0 kg (11.9) in 2006 (ES of 0.07). The overall gain in body mass was 5.4% from 1996 to 2006 (ES of 0.40) (Table 3).

Table 1
Table 1:
Change in 1RM BP and BT Pmax strength across a 10-year period in elite professional rugby league players expressed as the mean (SD).*†
Table 2
Table 2:
The ES statistics for changes in 1RM BP expressed from 2 different starting points—years 1996 and 2000.*
Table 3
Table 3:
The ES statistics for changes in BT Pmax expressed from 2 different starting points—years 1997 and 2000.*

Discussion

This study details the changes in strength and power across a 10-year period by a number of athletes who became members of both a World Champion Club and World Champion national representative team. While all the athletes possessed at least 2–3 years of resistance training experience before 1996, this study tracks the scope and magnitude of their strength and power changes across 2 important phases of their professional careers. The nature, scope, and possible reasons for any changes will be discussed below.

Across the multi-year period, the athletes improved maximal strength despite moderately high initial strength levels. The initial strength levels of 1996 exceed the average that had been previously reported for large groups of professional rugby league players (40), perhaps indicating the intensive resistance training history and quality of the subjects compared with other professional rugby league players. From 1996 to 2000, the change in strength was large (as determined by ES); however, the change in strength from 2000 to 2006 was designated as small. This is in agreement with previous work that has revealed that maximum upper body strength can still be increased in experienced strength-power athletes across multi-year periods; however, there seems to be a diminishing degree of positive adaptation with increased training experience (2,9,13). This study also reveals that once players become established at the highest level, the small changes in strength and power that may occur may actually require a multi-year period to manifest. In this instance, it required 6 years for the change in strength to be deemed an SWC. However, it is most likely that the inappropriate implementation of S-E training in 2004 and its cessation in late 2005 exerted some influence on the changes in maximal strength in 2006. This will be discussed in more depth below.

The results for changes in maximal power (BT Pmax) largely reflected the changes in 1RM BP, with large changes (as determined by ES) from 1997 to 2000 and a small change (as determined by ES) after year 2000 till 2006. For example, over the 10-year period, the BT Pmax increased by 23%; however, most of these changes occurred within the first 3-year period indicating diminished progress with increased training experience. Again it is most likely that the inappropriate implementation of S-E training in 2004 and its cessation in 2006 exerted some influence on the changes in maximal power. This will be discussed in more depth below.

On a cross-sectional basis, the relationship between maximum strength and power has already been clearly established (5–10,12–14,16,41). Of importance to coaches is the longitudinal relationship, that is, how do changes in strength relate to changes in power over long-term periods?

While 6 subjects makes statistical power interpretations like this very problematic, it is interesting to note that the magnitude of the correlation between the change in strength and the change in power (r = 0.77) in this investigation was very similar to what has been reported before for longer-term upper body studies with greater number of subjects (e.g., for 4 years: r = 0.75, n = 12 (16); for 6 years, r = 0.93, n = 11 (9); and for 5 months: r = 0.73, n = 19 (6)).

Consequently, given the limitations of the low subject number and associated low statistical power, this study may reinforce previous conclusions that long-term changes in power output are heavily reliant on changes in strength in experienced resistance trainers (9,13,16). It strongly suggests that increasing maximum strength is of extreme importance to athletes who need to increase maximum power. However, given the diminishing scope for strength improvements with increased training experience and the multifaceted nature of power, other methods of training to increase power, other than solely through maximum strength training, may also need to be embraced (15,44).

The basic arguments for why only ES and SWC occurred in strength and power in the final 6 years of this observation can come down to a number of key points. First, the athletes investigated are not truly specialist strength/power athletes, and their variety of training and the nature of their sport does not allow them to continually, specifically, and solely address strength/power enhancement. Second, Sale (45) has posited that a strength/power ceiling may exist which is hard to surpass without either adding muscle mass or via illegal pharmacological enhancement. Aligned with both possible explanations is the concept of LTAD and multiyear periodization proposed by Balyi et al. (18–20), whereby elite athletes in the Training to Win stage are actually more concerned with maintaining their already high strength and power levels while they concentrate more upon factors associated with winning at elite level competition. These main points are discussed in more detail immediately below.

It can be argued that rugby league players are not pure strength-power athletes (like weightlifters and powerlifters) because of the large aerobic, anaerobic, and sprint volumes they complete both in games and in training (6,37–40). Powerlifters and weightlifters who are specialized in resistance training typically display much higher strength levels than the athletes in this investigation. If the athletes in this investigation were to perform more specialized resistance training and no other “conflicting” training, they would most likely increase strength and power. However, forgoing the holistic training regime necessary to prepare for rugby league in an attempt to bench press 1–2% more per year is neither possible nor plausible for these elite athletes to contemplate as this scenario may actually decrease their rugby league sports performance by detracting from their conditioning, running speed, and skill and tactical training. When high running conditioning volumes and concurrent resistance training are presented in a well periodized manner, they may not actually decrease the strength/power capabilities of elite rugby league/union players such as these, however, they might make further gains in strength and power more difficult to realize (1,2,6).

Another reason why only small ES and SWC's in strength and power occurred during the latter years of the investigation could be ascribed because of the high impact forces and physical collision nature of the game and the fact that the players wear no or little protective padding in the NRL (25,37–39). In rugby league, the collisions and tackling are performed mainly with the anterior musculature/joints (25), which are the ones involved in bench pressing and bench throwing exercises. Extremely high levels of muscle damage (as evidenced by creatine kinase, CK, levels) occur as a result of professional rugby league match play (37–39). Often, games are scheduled only 5 days apart when clearly CK have not returned to baseline levels, indicating incomplete muscular recovery before the onset of the next dosage of blunt force trauma (37–39). An accumulation of collision-generated muscular and joint traumas over the years could attenuate strength/power development in these exercises (12), a situation that does not occur for specialist athletes like weightlifters and powerlifters.

In a study by Baker and Newton (13), 2 subgroups were identified, based on the strength levels and resistance training age at the beginning of the observation. The less strong and experienced group made greater gains than the more experienced group overall and within each 2-year period of the 4 years, despite following the same resistance program. However, during the final 2 years, the more experienced group exhibited only a 2.0% increase in 1RM BP (similar to the change in strength exhibited by elite weighlifters in the work of Häkkinen et al. (33)), whereas the other group exhibited an 8.1% increase in 1RM BP. It was concluded at the time that “the Sub-elite group are two years behind the Elite group in age and training experience in 1998 and hence the scope of adaptations experienced by the Sub-elite group for the final two year period from 2000 to 2002 is similar to the first two years of the Elite group. Thus, it could be posited that the progress that the Sub-elite group make in the next two year period may also be quite small (13).” It seems that this supposition was correct and in fact minimal change in strength occurred. With increased strength/power training experience and levels, it seems to become increasingly difficult to make improvements in these parameters, and Sale (45) has postulated that a “strength ceiling” exists. From this point, Sale has theorized that, apart from illegal usage of anabolic steroids, only adding muscle mass could bring about large strength increases. Although strength may be greatly increased if athletes gain lean body mass (3), the changes in body mass in this investigation (approximately 6.5%) occurred in the first stage where significant changes in strength and power also occurred. After this point, during the Training to Win stage, the changes in body mass were deemed trivial in nature, and accordingly, the changes in strength and power were difficult to obtain.

Rugby league players who are already established at the elite level deem large body mass increases (lean or otherwise) to be inappropriate and unwanted because they believe large body mass increases potentially reduce running fitness. This belief has been confirmed by a study that has shown that high body mass is strongly related to lower running velocity at lactate threshold and accordingly decreases in running ability over 10-km distances (22). Given that the players have to run up to 8 km in a game (37–40), increasing body mass over the players' already established optimum level to increase strength/power levels is not a viable option because it will detract considerably from their on-field running performances. Thus, the 2 methods that Sale (45) postulated of bursting through the strength ceiling are not plausible for these athletes.

Therefore, the concept of a strength ceiling does seem to exist; however, it may be considered in 2 parts: a true strength ceiling that exists even for specialist strength athletes performing only training necessary to increase strength and power (i.e., competitive weightlifters and powerlifters) and a lower “false” ceiling that exists for sports athletes who have to perform a more varied and holistic training regime that does not permit only specialized strength/power training or large increases in body mass. As all of the athletes possessed a minimum of 2–3 years regimented strength training experience before this investigation started in 1996, coupled with the 10 years of this investigation, it may indicate that a strength “ceiling” (plateau) of sorts may be reached after ≥4 to 7 years of intense regimented resistance training. Very small changes in strength can occur after this point; however, they may take a number of years to manifest themselves.

According to Balyi et al. (18–20), elite athletes in late specialization sports such as rugby league progress through 4 stages of physical development and allied training. The latter 2 stages, the “Training to Compete” and “Training to Win” stages which encompass the chronological ages of 16–19 years and 20+ years, respectively, are of interest to this investigation. In the Training to Compete stage, the athletes begin to perform the necessary specialized training that will enable them to compete physically with the elite performers of their sports. In a “late specialization sport” such as rugby league, this is typically regimented strength/power training and intense running conditioning. Typically, these types of athletes will continue to gain in physical qualities for 2 years after entering the Training to Win phase (19) (i.e., until they are established elite athletes, age: 21 to 22+ years). Training to maintain, rather than increase, physical qualities such as strength and power becomes the norm after this point as elite athletes tend to focus more upon competition and perfecting the sports skills and strategies associated with winning.

In support of this, most of the athletes in this investigation became elite international athletes during the course of the investigation, which did indeed bring about big changes in the length and content of their preparation and competition periods. Throughout the period of investigation, all of the subjects were selected to represent the Australian National team at the end of the domestic professional NRL season. This entailed them playing international games for an extra 8 weeks in comparison to other elite or sub-elite players, and accordingly, their preparation period for the following season was reduced by 8 weeks. From 2000 onwards, the preparation period aimed at developing strength and power for these players was less than 6 weeks before the commencement of in-season “maintenance” training. Essentially, competition requirements over-rode physical development training requirements and elite athletes cannot be expected to increase strength and power levels under such conditions. Accordingly, it can be seen that the athletes in this investigation followed the LTAD pattern of training and competition proposed by Balyi et al. (18–20), and their small change in strength and power after year 2000 should be seen as a normal process for sports athletes whose competition demands over-ride physical development training requirements.

Because of the rule changes in the game, the skill coaching staff requested that the athletes increase the S-E content of their training in 2004 and 2005. While the decrements in strength and power were not of an extent to meet a negative small change, the fact that the cessation of such training in the preparation period for 2006 brought about a small positive SWC in strength and power is of interest. It has been shown in rugby league players that high volume–load training exerts an immediate, large, and significant decrease in upper body power output and this negative influence is also significantly greater and longer lasting in stronger athletes compared with less strong athletes (17). Given that the athletes in this study were much stronger than the athletes in the previous study, it could be posited that the high volume S-E training exerted some degree of negative influence on the athletes strength and power levels. So while the concepts of the strength ceiling and LTAD exert major influence on the scope and magnitude of strength and power gains, the acute programming must also mediate the acute manifestation of strength and power in elite athletes. It is not known how long the deleterious effects of high volume–load training last in strong elite athletes and also how this when coupled with the blunt force trauma of rugby league games and training, affects strength and power levels.

Practical Applications

This long-term observation of changes in upper body strength and power output in experienced resistance trainers across 10 years has supported the earlier work concerning the limited scope for improvements in upper body strength and power with increased training experience.

Maximum upper body strength can still be increased in advanced strength-power athletes; however, the degree of improvement diminishes with increased strength and training experience, and the time frames over which an observable increase in strength may be observed may become quite lengthy in more advanced athletes. Maximum upper body power, because it is strongly related to maximum strength, follows a similar pattern in terms of diminishing increases in power with increased training experience and power levels.

However, a ceiling of sorts for strength and power gains may exist after 4–7 years of resistance training experience if athletes do not have the luxury of gaining lean body mass. According to the concept of LTAD, this may not be a problem if the athletes can maintain these high levels of strength and power while perfecting their sports performances. Irrespective of these major mediating factors, inappropriate acute programming, such as high volume S-E training, may possibly negatively affect the manifestation of strength and power.

Future research and work by strength coaches should focus upon methods, programs, and nutritional strategies that address the needs of long-term training in experienced resistance trainers. To date, much of the training of these athletes is based upon the empirical evidence/methods (which may or may not be appropriate) or the results of short-term training studies on lower-level athletes or university students, who are not applicable.

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Keywords:

long-term; adaptations; bench press

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