American and rugby-style football both require a

Transcription

1 Journal of Strength and Conditioning Research, 2001, 15(2), National Strength & Conditioning Association The Effects of an In-Season of Concurrent Training on the Maintenance of Maximal Strength and Power in Professional and College- Aged Rugby League Football Players DANIEL BAKER School of Sport and Exercise Science, University of Sunshine Coast, QLD, Australia ABSTRACT Fourteen professional (NRL) and 15 college-aged (SRL) rugby league players were observed during a lengthy in-season period to monitor the possible interfering effects of concurrent resistance and energy-system conditioning on maximum strength and power levels. All subjects performed concurrent training aimed at increasing strength, power, speed, and energy-system fitness, as well as skill and team practice sessions, before and during the in-season period. The SRL group significantly improved 1 repetition maximum bench press (1RM BP) strength, but not bench throw (BT Pmax) or jump squat maximum power (JS Pmax) over their 19-week in-season. The results for the NRL group remained unchanged in all tests across their 29-week in-season. The fact that no reductions in any tests for either group occurred may be due to the prioritization, sequencing, and timing of training sessions, as well as the overall periodization of the total training volume. Having athletes better conditioned to perform concurrent training may also aid in reducing the possible interfering effects of concurrent training. Correlations between changes in 1RM BP and BT Pmax suggest differences in the mechanisms to increase power between stronger, more experienced and less strong and experienced athletes. Key Words: bench press, bench throw, jump squat, endurance Reference Data: Baker, D. The effects of an in-season of concurrent training on the maintenance of maximal strength and power in professional and college-aged rugby league football players. J. Strength Cond. Res. 15(2): Introduction American and rugby-style football both require a high degree of strength and power for successful competition. Although strength and power may be relatively easily developed during off- and preseason training periods, there is some disagreement as to whether preseason levels of strength and power can be maintained during the long in-season playing periods, especially when a large amount of energy-system (aerobic and anaerobic) conditioning or lengthy team practices are performed (2, 7, 9, 17, 24). For example, it has been demonstrated that an acute decrease in strength and high-speed torque occurred when resistance training was preceded by a regime of 25 minutes of mixed, high-intensity aerobic and anaerobic conditioning (18). This finding would be of consequence to strength and conditioning coaches of sporting teams where resistance training and a large amount of conditioning and/or team practice (e.g., football and rugby) must be performed. A number of studies have investigated whether strength could be maintained across a sporting season in football-type sports despite the increased game/ practice and/or conditioning demands. Fleck and Kraemer (9) and Baker (2) reported that strength could be maintained weeks into the in-season in college and professional rugby-style football players, respectively. However, Schneider et al. (24) and dos Remedios et al. (7) reported significant losses in strength weeks into the in-season in college football players. More recently, Legg and Burnham (17) reported losses in shoulder strength by as much as 25% over the course of a 10-week in-season period in college-aged football players. It was thought that the energy-system demands of practice and games may partly be responsible for reduced strength levels listed in the studies above. Conflicting neural patterns, fiber recruitment, and hormonal outputs that arise from high-volume energy-system training may also be detrimental to strength and power development (8, 11, 13 16). These studies have only investigated strength, whereas Kraemer et al. (16) have shown that muscle power is more susceptible to interference from a prolonged period of concurrent resistance and condition- 172

2 Effects of Concurrent Training on Maintenance Strength and Power 173 ing training. To date no studies have examined the effect of concurrent training or the demands of an inseason of playing and practice on muscle power in football-type athletes. The purpose of this paper is to report on maximum strength and power levels in professional and collegeaged rugby league football players throughout an entire in-season period. This in-season period would entail the concurrent training of energy-system conditioning, strength and power, and numerous skill and team practice sessions. Methods Subjects Fourteen professional national rugby league (NRL) and 15 college-aged rugby (SRL) league football players agreed to participate and were tested as part of their regular strength and conditioning program requirements for their sport. The mean SD age, height, and body mass were years, cm, and kg, and years, cm, and kg, respectively, for the NRL and SRL players. Testing Maximal strength was assessed using the 1 repetition maximum bench press (1RM BP) using the methods previously outlined (6). The maximal average power output (Pmax) was assessed utilizing the plyometric power system, which has been described previously (3, 4). Lower-body power was assessed during jump squats (JS Pmax) with resistances of 40, 60, 80, and 100 kg using the methods described previously (3, 4). Upper-body power output (BT Pmax) was assessed during flat bench press throws with resistances of 40, 50, 60, 70, and 80 kg using the methods used previously described (5). Testing conducted at the completion of the preseason training period (Pre) served as the base level for further comparison. Throughout the in-season period the SRL group were tested on 2 more occasions, at week 9 and week 19. However, due to minor gamerelated lower-body injuries, JS Pmax data for all 3 test occasions can only be reported for 11 of the subjects. For the NRL group, upper-body testing of strength and power was performed an additional 3 times (weeks 8, 17, and 29). Due to a small number of gamerelated lower-body injuries, the JS Pmax data for the NRL group will be reported for the Pre test and week 29 test only. Only 13 of the subjects completed both of these lower-body testing sessions. This testing at different periods provided data pertinent to whether strength and power could be maintained at the peak levels recorded at the completion of the preseason training cycle throughout the lengthy inseason period. Morning Afternoon AR* Tuesday WT SK Condit. TP Condit. SK/TP WT SK Condit. TP Table 1. Example of a weekly in-season training plan for the professional rugby league (NRL) group (game on Sunday). Monday Wednesday Thursday Friday Saturday TP *AR active recovery; WT strength and power training; SK Skill training; Condit. energy system conditioning; TP team practice. Training Prior to the Pre testing, which occurred at the beginning of the competitive season, the subjects had completed a minimum of 16 (SRL) and 8 weeks (NRL) of a periodized cycle of concurrent resistance and conditioning training. This entailed 4 resistance-training sessions (2 upper and lower body), 3 high-intensity running sessions (45 60 minutes each), and 3 skill and team practice sessions (45 60 minutes each) per week. The professional NRL group also performed 2 conditioning sessions for the upper body (e.g., swimming, boxing, wrestling, arm cranking, and rowing, minutes each). All of the subjects from both groups attained or bettered previous personal bests on the 1RM BP at the Pre test, indicating a high training status at the start of the investigation. These results and the lengthy preseason training period and training age of the subjects would tend to preclude any changes in strength or power during the ensuing in-season period being because of a simple neural or learning effect (10, 20). During the in-season investigation period, resistance training was reduced to 2 whole-body sessions per week using the methods previously outlined (1, 2). Conditioning was reduced to 2 3 high-intensity, minute sessions per week. Skill and team practice sessions, which also have an inherently high degree of energy-system conditioning stimulus, were usually carried out 3 5 times per week for approximately 60 minutes each. The NRL group also performed 1 upperbody conditioning session per week for the first 8 weeks of the in-season. An example of the in-season weekly training plan for the NRL group is detailed in Table 1. Training volume and intensities during the in-season period were periodized in 3 4 week cycles according to the methods outlined (2). Consequently, highvolume, lower-intensity resistance-training weeks were aligned to high-volume, lower-intensity energysystem conditioning training weeks and low-volume, high-intensity resistance-training weeks were aligned

3 174 Baker Table 2. The maintenance of different measures of strength and power by professional rugby league (NRL) players across a 29-week in-season period (Mean SD). Pre Week 8 Week 17 Week 29 1RM BP* BT Pmax JS Pmax * 1RM BP 1 repetition maximum bench press; BT Pmax bench throw maximum power; JS Pmax jump squat maximum power; Pre preseason training period. Table 3. The maintenance of different measures of strength and power by college-aged rugby league (SRL) players across a 19-week in-season period (Mean SD). Pre WK 9 WK 19 1RM BP BT Pmax JS Pmax * * RM BP 1 repetition maximum bench press; BT Pmax bench throw maximum power; JS Pmax jump squat maximum power; Pre preseason training period. * Denotes significantly different (p 0.05) from the Pre test result. to low-volume, high-intensity energy-system conditioning training weeks. This procedure ensured a methodical periodization of the total training stress. Thus the first weeks of a training cycle were high in total volume stress (both energy-system conditioning and resistance-training volume), whereas the latter weeks were low in the total volume stress. Statistical Analyses The results for 1RM BP, BT Pmax, and JS Pmax were compared using a repeated measures 1-way analysis of variance (ANOVA) to determine if any of the inseason tests differed from those of the end of preseason baseline scores or to each other. If a significant effect of test occasion was found, Fisher post least squares difference post hoc comparisons were performed to determine which test occasions produced results. Pearson s moment correlations were used to determine the strength of relationships between variables. Statistical significance was accepted at an alpha level of p Results The results for the maintenance of various measures of strength and power are contained in Tables 2 and 3. For the NRL group, maximal upper-body strength (1RM BP) and power (BT Pmax) were maintained at the preseason levels across the entire season. Lowerbody maximal power (JS Pmax) was also unchanged between the preseason and week 29 tests. For the SRL group, 1RM BP improved significantly by 4.9% from the Pre test maximum to the week 9 testing occasion. It then remained unchanged until the week 19 test. JS Pmax was unchanged between each test occasion for the SRL group. Discussion The results of this investigation are in line with the results of some previous studies that have examined the maintenance of different measures of strength across an in-season period, typically weeks (2, 9). However, the results are at odds with those of Schneider et al. (24), dos Remedios et al. (7), and Legg and Burnham (17) who reported significant losses in strength throughout in-seasons of similar length, despite the continuation of strength training. In the current study the college-aged athletes actually significantly increased strength. Schneider et al. (24), who reported an 8% decrease in BP strength in Canadian college football players during a 16-week in-season, rationalized that the increased energy-system demands of the Canadian game, as opposed to the American game, may in part explain the differences in their results compared with Fleck and Kraemer (9). However, rugby league players cover distances of 5 8 km (19) or more per 80-minute game, as well as during 3 5 training sessions per week, yet the college-aged players in this study exhibited an increase in strength despite this large conditioning workload. Given the results of this study and previous studies of rugby football players (2), the conclusion of Schneider et al. (24) may not be totally valid. The reasons why the SRL athletes in this study increased strength, as opposed to the losses in strength reported by Schneider et al. (24), dos Remedios et al. (7), and Legg and Burnham (17) may be due to their apparent ability to better handle the interfering effects of concurrent training. It has been postulated that athletes who typically perform little energy-system training in the preseason and who may possess low aerobic capacities may experience greater decreases in maximal strength during the in-season than do athletes with a long training history of concurrent strength and energy-system training (7). If athletes are better conditioned to perform concurrent resistance and energysystem training, then the interfering effects of energysystem training, game and practice demands on strength development, or maintenance may be reduced to some degree. In support of this, the subjects in the Kraemer et al. (16) study also maintained strength despite a large amount of concurrent energysystem and resistance training. Therefore it could be argued that the SRL subjects who performed 16 weeks

4 Effects of Concurrent Training on Maintenance Strength and Power 175 of concurrent training prior to the Pre testing period may have become better conditioned to perform concurrent training such that it did not negatively affect their strength levels during the in-season. Why the NRL group maintained, but did not gain strength, as did the SRL group, is most likely due to their greater strength-training background, which reduces the scope for strength improvements (10). Elite athletes may train for up to 2 years before a 2.5-kg increase in strength is manifested (12). Similar to the report of Hakkinen (10), the SRL and NRL groups utilized the same resistance-training programs and all subjects attained or bettered personal bests in the 1RM BP at the Pre testing occasion, indicating a high initial training status. However, the NRL group were unable to further increase strength across 29 weeks. This result may tend to confirm the limited scope for improvements in strength in athletes who possess greater strength-training experience (10, 12). This study differed from previous studies in that it examined the possible interfering effects of concurrent energy-system conditioning not only on strength, but more importantly on power output for the upper and lower body, across a long-term period. This study of power output levels has yielded interesting results. First, upper- and lower-body power can be maintained for up to 29 weeks despite the large degree of lower- and upper-body conditioning that is performed to improve the athlete s ability to resist fatigue. There has been scant research on the maintenance of maximal power outputs by subjects during prolonged periods of concurrent training. Kraemer et al. (16) reported that maximum strength was maintained but that power, as assessed during a Wingate test, was not maintained in athletes performing concurrent training. It was postulated that a high volume of total training stress would appear to be the main interfering effect on power output (15, 16). In the current study subjects performed high total workloads, but based on the results and recommendations of previous research, a number of strategies were implemented in an attempt to reduce the possible interfering effects of concurrent training on power output. These strategies were the prioritization of training goals, the sequencing of training sessions, the timing of training sessions (18), improving the condition of the athlete to perform concurrent training (7), and the periodization of the total training stress (15). Insofar as prioritization, sequencing, and timing of sessions, Leveritt and Abernethy (18) suggested that training goals needed to be prioritized so that the primary training goal should be trained first in an unfatigued state. This prioritization of training goals would then dictate the sequencing and/or timing of other training sessions. This may be valid for athletes who are deficient in a particular component of fitness or strength. However, Nelson et al. (22) found no suppression of strength development if strength training precedes conditioning training. If conditioning training is performed later in the day, in an already semifatigued state, this would actually increase the demands on the athlete to resist fatigue, which is often the goal of conditioning training. The subjects in this study did not perform conditioning training before strength and power training in an effort to reduce the likelihood of acute interference between conditioning training and power output. Therefore, to reduce the likelihood of interfering effects between different forms of training, it is recommended to perform strength and power training before (22) or on alternate days to conditioning training (23). If sessions are to be performed on the same day, then attempts should be made to increase the amount of time between sessions to allow for glycogen repletion (18). Studies have shown that athletes performing concurrent energy-system and strength training become accustomed to training such that strength is not always significantly affected (16, 22, 23). How the neuromuscular and hormonal systems manage this is still unknown. However, it is thought that an effective periodization of the total stress of combined training enables the athlete to better adapt to this training scenario (15). For athletes such as rugby league players who require high levels of energy-system fitness as well as strength and power, an effective periodization plan may be necessary to control the total training stress imposed on the athlete. In this case, the athletes performed 3 4 week cycles with the highest volume and lowest intensity for both resistance and energy-system training performed in the first week, progressing to the highest intensity and lowest volume in the last week of a cycle (2). These high-intensity, low-volume training weeks always preceded the games of perceived greatest difficulty. For the athletes involved in this study, this periodization procedure must be at least partly responsible for their maintenance of strength and power across a 19- and 29-week in-season. However, it must be noted that during this investigation Pmax was only tested during weeks of lowervolume, higher-intensity training at the conclusion of a training cycle, as per the periodization plan. It is quite possible that if Pmax was tested during the weeks of the highest workloads, then Pmax levels may be temporarily suppressed. Also, if an acute bout of energy-system conditioning can result in an acute decrease in strength and high-speed torque (18), then it could be presumed that there would be an acute effect on power output as well. Therefore it would appear that strength and conditioning coaches may need to implement the types of strategies discussed above to reduce the possible interfering effect of concurrent

5 176 Baker training on strength and power output over a longterm (e.g., in-season) period. Of interest is the relationship between changes in strength (1RM BP) and the changes in power (BT Pmax) across an in-season. In the current investigation the relationship between changes in strength and changes in power were r 0.73 (p 0.05) and r 0.39 (not significant), respectively, for the college-aged SRL and professional NRL rugby league players. These results illustrate that for the SRL athletes, who possess lower levels of strength and power, changes in Pmax are still highly dependent on changes in maximum strength. However, it appears to become less so with the increased training experience of the NRL athletes. As the cross-sectional relationship between maximum strength and Pmax is usually in the order of r (4, 21), then the results for changes in these parameters must indicate a decreasing transfer effect that may be occurring with increased training experience. This is most likely because of the fact that the NRL athletes have (generally) already attained their strength base, from which further gains in maximum strength are difficult to achieve without inappropriately directing specialized training in that direction, and hence gains in Pmax are occurring through avenues other than the development of strength. Thus for these more elite athletes to increase power they must do so through increased velocity/ speed contributions. Accordingly, for these elite athletes gains in strength, which will be minimal, will not largely account for changes in power. Consequently, the total training stress or the acute effects of changes in the sequencing, timing, or volume of training sessions may impact more on power levels than the minimal changes in strength could. Furthermore, as power output can appear acutely (negatively) affected by the volume of training, whereas maximum strength is less affected (16), then statistically there can be little relationship between changes in the 2 variables at higher levels of adaptation if power decreases because of the effects of volume training, whereas maximum strength remained stable. The evidence of the correlations between 1RM BP and BT Pmax at different testing periods may tend to confirm the theory that the volume of training acutely affects power output in some manner (see Table 4). For the SRL the relationship between 1RM BP and BT Pmax remained remarkably stable (r ) across all testing occasions, whereas it varied more for the NRL group (r ). The relationships between 1RM BP and BT Pmax become fairly similar for each group by the third testing session, but are markedly dissimilar during the first 2 testing occasions. The only factors that differentiate between the 2 groups at these first 2 testing sessions are training age (and consequently strength and power levels) and the fact that the NRL group also performed additional upper-body Table 4. Correlations between strength (1RM BP) and power (BT Pmax) at different testing occasions. All correlations are significant (p 0.05). NRL SRL 1RM BP v BT Pmax* Test 1 Test 2 Test 3 Test * 1RM BP 1 repetition maximum bench press; BT Pmax bench throw maximum power; NRL professional rugby league players; SRL college-age rugby league players. energy-system conditioning. As by the third testing session (weeks 17 and 19) the relationships between 1RM BP and BT Pmax are similar for both groups and the difference in training age is stable, then the extra upper-body conditioning of the NRL group, which had been discontinued after week 8, may be accountable for these changes. It is likely that the addition of a large volume of upper-body conditioning in the preseason and the first 8 weeks of the in-season lowered the relationship between strength and power for the NRL group. When the upper-body conditioning was eliminated, the relationships returned to virtually the same level as compared with the SRL group. This may further indicate that the volume of training has more impact, through as yet unknown mechanisms, on power rather than strength. Based on this and the previous cross-sectional data (4, 21), it would appear that in the early training ages the neuromuscular system adopts the strategy of increasing Pmax by predominantly utilizing increases in strength. As gains, or potential gains in strength diminish, then changes in Pmax must be produced through other velocity-oriented means. Therefore a diminished relationship between changes in strength and changes in Pmax must occur with increased training experience. Of interest would be the relationship between changes in velocity or total training volume and changes in Pmax over long-term training periods in advanced athletes performing concurrent resistance and energy-system training. Practical Applications Maximal strength and power can be maintained at the maximum preseason levels for long in-season periods of up to 29 weeks despite a large amount of concurrent energy-system training and a reduction in strength-training volume. The key to maintaining strength and power during the in-season may lie in having athletes initially better conditioned to perform concurrent training; the prioritization, sequencing, and timing of training; and utilizing an appropriate periodization model that allows for periods of high, me-

6 Effects of Concurrent Training on Maintenance Strength and Power 177 dium, and low training volumes and intensities. With an increased training age there appears to be a decreasing transfer between changes in maximum strength and maximum power. This may be due to a plateau affect of strength and the neuromuscular system seeking other avenues (e.g., velocity) to increase power. The total volume of training may also need to be effectively periodized or managed such that its potential to acutely effect power output is minimized. References 1. BAKER, D. Strength training for rugby leagues. In: Proceedings of the 1995 Australian Strength and Conditioning Association National Conference and Trade Show.. I. King, ed. Toowong, QLD, Australia, pp BAKER, D. Applying the in-season periodisation of strength and power training to football. Strength Cond. J. 20(2): BAKER, D., AND S. NANCE. The relation between running speed and measures of strength and power in professional rugby league players. J. Strength Cond. Res. 13: BAKER, D., AND S. NANCE. The relation between strength and power in professional rugby league players. J. Strength Cond. Res. 13: BAKER, D., S. NANCE, AND M. MOORE. The load that maximizes the average mechanical power output during explosive bench press throws in highly trained athletes. J. Strength Cond. Res. 15: BAKER, D., G. WILSON, AND R. CARLYON. Generality versus specificity: A comparison of dynamic and isometric measures of strength and speed-strength. Eur. J. Appl. Physiol. 68: DOS REMEDIOS, K.A., R.L. DOS REMEDIOS, S.F. LOY, G.J. HOL- LAND, W.J.VINCENT, L.M. CONLEY, AND M. HING. Physiological and field test performance changes of community college football players over a season. J. Strength Cond. Res. 9: DUDLEY, G.A., ANDDJAMIL, R. Incompatibility of endurance and strength training modes of exercise. J. Appl. Physiol. 59: FLECK, S.J., AND W.J. KRAEMER. Designing Resistance Training Programs. Champaign, IL: Human Kinetics, HAKKINEN, K. Factors influencing trainability of muscular strength during short-term and prolonged training. Natl. Strength Cond. Assoc. J. 7(2): HAKKINEN, K. Effects of the competition season on physical fitness profile in elite basketball players. J. Hum. Move. Stud. 15: HAKKINEN, K., A. PAKARINEN, M. ALEN, H. KAUHANEN, AND P. KOMI. Neuromuscular and hormonal adaptations in athletes to strength training in 2 years. J. Appl. Physiol. 65(6): HICKSON, R. Interference of strength development by simultaneously training for strength and endurance. Eur. J. Appl. Physiol. 45: HUNTER, G., R. DEMMENT, AND D. MILLER. Development of strength and maximum oxygen uptake during simultaneously training for strength and endurance. J. Sports Med. Phys. Fitness 27: KRAEMER, W.J., AND B.C. NINDL. Factors involved with overtraining for strength and power. In: Overtraining in Sport. R.B. Kreider, A.C. Fry, and M.L. O Toole, eds. Champaign, IL: Human Kinetics, pp KRAEMER, W.J., J.F. PATTON, S.E. GORDON, E.A. HARMAN, M.R. DESCHENES, K. REYNOLDS, R.U. NEWTON, N.T. TRIPLETT, AND J.E. DZIADOS. Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations. J. Appl. Physiol. 78: LEGG, D., AND R. BURNHAM. In-season shoulder abduction strength changes in football players. J. Strength Cond. Res. 13: LEVERITT, M., AND P.J. ABERNETHY. Acute effects of high-intensity endurance on subsequent resistance activity. J. Strength Cond. Res. 13: MEIR, R., D. ARTHUR, AND M. FORREST. Time and motion analysis of professional rugby league: A case study. Strength Cond. Coach 1(3): MORITANI, T., AND H.A. De Vries. Neural factors versus hypertrophy in the time course of muscle strength gain. Am. J. Phys. Med. Rehabil. 58(3): MOSS, B.M., P.E. REFSNES, A. ABILDAARD, K. NICOLAYSEN, AND J. JENSEN. Effects of maximal effort strength training with different loads on dynamic strength, cross-sectional area, loadpower, and load-velocity relationships. Eur. J. Appl. Physiol. 75: NELSON, A.G., D.A. ARNALL, S.F. LOY, L.J. SILVESTER, AND R.K. CONLEE. Consequences of combining strength and endurance training regimens. Phys. Ther. 70: SALE, D.G., I. JACOBS, J.D. MACDOUGAL, AND S. GARNER. Comparison of two regimens of concurrent strength and endurance training. Med. Sci. Sports Exerc. 22: SCHEIDNER, V., B. ARNOLD, K. MARTIN, D. BELL, AND P. CROCK- ER. Detraining effects in college football players during the competitive season. J. Strength Cond. Res. 12: