Rugby union can be characterized as a field-based, high-intensity collision sport where players are required to perform activities of short duration and high intensity separated by recovery periods of varying duration. The nature, frequency, and duration of the work and recovery periods can vary significantly depending on player position (9). For example, it has been calculated that the average frequency of sprints per game ranged from 8 ± 6 for front row players to 13 ± 5 for outside backs, and the average frequency of tackles per game was 13 ± 5 for back row players and 7 ± 4 for outside backs (10). On the basis of the work by Duthie et al. (10), it is clear that rugby players are required to perform activities along the strength and power continuum, with some activities classed as low force-high velocity (e.g., sprinting, accelerating, and rapid changes of direction), some classed as high force-low velocity (e.g., scrummaging, mauling), and, finally, activities such as tackling can be classed as high force-high velocity. Given the multifaceted demands of the game of rugby, the development of strength and power are fundamental to success in this sport.
Investigations have been conducted to examine various training protocols purported to enhance power development in athletes. These training methods have included athletes trying to develop power while working against their body mass (e.g., plyometrics) and also while working against external loads that equate to various intensities of their 1 repetition maximum (1RM) (40-70% during upper-body exercises [5,28], body mass -60% for lower-body exercises [19,26], and 80-100% for Olympic-style weightlifting movements [22,23]).
More recently, a method receiving significant attention called complex training has been suggested to be an effective training method for enhancing power output in athletes (3,13). Complex training alternates a heavy resistance exercise (HRT) with a biomechanically comparable plyometric exercises in the same workout (21) with the intention of increasing the power output during the plyometric exercise. In addition, this method may have even greater application for rugby players who frequently have to generate force against a range of contrasting loads, for example, when performing a scrum (high force) followed by a sprint (low force).
Research examining the effectiveness of complex training has produced contradictory results. For example, after HRT (>80% 1RM), subsequent muscle performance has been demonstrated to decrease (12,21), whereas other studies have reported increases in performance (3,7). The observed decrease in performance can be attributed to muscle fatigue associated with the HRT (e.g., low intramuscular stores of phosphocreatine), whereas the increase in muscle performance observed has been attributed to a condition referred to as postactivation potentiation (PAP) (15). On the basis of the above statements, it is clear that both fatigue and PAP can coexist in skeletal muscle, and muscle performance after HRT depends on the balance between muscle fatigue and muscle potentiation (25).
To date, the majority of studies have concentrated on the effects of PAP on lower-body performance (e.g., jumping ability) (15,29,30); however, more recently, researchers have started to investigate the effectiveness of complex training on upper-body performance (3,4). For example, Baker (3) reported significant improvements in bench press throw performance of 4.5% after a set of 6 repetitions at 65% of the subjects' 1RM. Nevertheless, not all studies have found a positive effect with upper-body complex training. Hrysomallis and Kidgell (17), Ebben et al. (12), and Brandenburg (6) all failed to demonstrate any improvement in upper-body power output in their studies after HRT. Some of this conflict in the literature regarding an athlete's ability to harness PAP can be explained by the numerous methodologic differences in the various studies, which include the magnitude of the preload, previous weight training experience, and strength levels of the subjects (16). Although the majority of these methodologic variations can be controlled for, there is no uniform agreement about the optimal recovery time between the HRT and subsequent explosive activity for the upper body, with studies reporting recovery periods ranging from 0 to 18.5 minutes (3,6,7,8,20,24,30). To date, only a few studies have attempted to directly examine the optimal recovery time between the HRT and subsequent explosive activity (8,20,24), and all the above-mentioned studies examined lower-body performance with no study to date examining upper-body performance.Therefore, in light of this, the aim of the present study was to determine the recovery time for maximal benefits between the HRT (3 sets of 3 repetitions at 87% 1RM) and subsequent upper-body performance in a group of professional rugby players.
Experimental Approach to the Problem
During this within-subject study, each subject was required to attend the laboratory on 2 occasions. The objective of the first testing session was to determine the subjects' 3RM on the bench press and familiarize the subjects to the study procedures that were to follow. During the main experimental trial, subjects completed a baseline ballistic bench press (BBP), then, after a 10-minute recovery period, subjects were required to complete 3 sets of HRT (3 sets of 3 repetitions at 87% of the subjects' estimated 1RM) on the bench press. Immediately after the HRT (within 15 s) and every 4 minutes after the preload stimulus, up to 24 minutes (4, 8, 12, 16, 20, and 24 min), the subjects completed a BBP.
Twenty-six professional rugby players (Table 1) from whom written informed consent had been obtained volunteered to take part in the present study, which was approved by the university ethics committee and carried out during the preseason (August-September). Subjects were recruited on the bases that they were engaged in structured weight-training programs for at least 2 years before the start of the study and were able to complete the bench press and BBP with correct technique as assessed by a qualified strength and conditioning coach. The average resistance training experience of the present group of subjects was 3.1 ± 1.6 years.
Before the beginning of the main experimental trial, subjects visited the laboratory to become familiar with the testing methods and to have their 3RM bench press measured. During this familiarization session, subjects also practiced performing the BBP with the aim to maximize throw height. In addition, all subjects in the present study had previously participated in an optimal loading for peak power output (PPO) using the BBP methods and were therefore well familiarized with the testing methods. Forty-eight hours after the familiarization and strength testing period, all subjects performed the main experimental trial.
Subjects reported to the laboratory on the morning of testing after having refrained from alcohol, caffeine, and strenuous exercise for 48 hours previously. After the measurement of each subject's height and body mass, subjects underwent a standardized warm-up, which comprised 5 minutes on a rowing ergometer, followed by a series of dynamic stretches with an emphasis on stretching the musculature associated with the bench press and BBP. After the warm-up, subjects completed a baseline BBP. After a recovery period, subjects completed the HRT on the bench press. Immediately after the HRT (within 15 s) and every 4 minutes after the HRT up to and including 24 minutes (e.g., at 4, 8, 12, 16, 20, and 24 min), the subjects repeated the BBP.
Consumption of water (500 mL) was permitted during each test. Room temperature was maintained between 20°C and 24°C. Verbal encouragement was given to maximize performance.
Before the start of the strength testing session, all subjects underwent a standardized warm-up that comprised light intensity rowing for 5 minutes, followed by a series of dynamic movements with an emphasis on warming up the musculature associated with the bench press. Subjects then performed 3 warm-up sets of 8 repetitions at 50% 1RM, 4 repetitions at 70% 1RM, and finally 2 repetitions at 80% of their 1RM. After the final warm-up set, subjects attempted 3 repetitions of a set load (3RM), and, if successful, the lifting weight was increased until the subject could not lift the weight through the full range of motion. All subjects had been previously exposed to 3RM testing for the bench press. A 5-minute rest was imposed between all attempts to allow subjects adequate time to replenish energy stores. The 3RM was determined after 3 to 4 attempts in all subjects. The bench press movement was carried out according to the International Powerlifting Federation rules (18).
Ballistic Bench Press
For the measurement of upper-body power, subjects completed BBP on a smith machine with the ballistic measurement system (BMS) attached. Upper-body PPO was tested during a BBP throw performed on a smith machine with a relative resistance of 40% of their predicted 1RM, which has previously been shown to be the optimal load for developing PPO in the upper body in rugby players in our laboratory (unpublished data). During each bench press throw, the subject was instructed to lift the bar from the starting position and throw it as high as possible. To avoid the effects of deceleration and achieve maximal bar velocity, the bar was released at the top of the range of motion. During each throw, subjects were required to keep their head, shoulders, and trunk in contact with the bench as well as their feet in contact with the floor.
Subjects completed 8 BBP at the following times: baseline, immediately after preload stimulus (approximately15 s), and then every 4 minutes up to and including 24 minutes. To ensure that any effect observed during this experiment was caused by the HRT, 10 subjects were required to complete 7 BBP after a standardized warm-up with 4 minutes of recovery between each BBP. This was carried out to ensure that, during the main experimental trial, there was no warm-up effect or fatigue effect from the subsequent countermovement jump. A repeated-measures one-way analysis of variance (ANOVA) revealed no significant time effect over the duration of the study (ES = 0.78, p = 0.759). The HRT consisted of 3 sets of 3 repetitions at 87% of the subjects' estimated 1RM on the bench press with 4 minutes of recovery between each set, which was performed approximately15 minutes after the baseline BBP.
Ballistic Measurement System
The BMS was used to collect bar displacement data during the BBP. Peak power output and throw height from the BBP were calculated using the software provided with the BMS. The BMS comprises a cable-extension potentiometer (distance transducer) that produces a variable voltage output in relation to the extension of the 3-m cable. An analogue to digital card then captured the voltage data with customized software, sampling at 500 Hz and converting the voltage data into displacement data. The BMS system was calibrated against known distances for the range on which the BBP were performed; this calibration was performed before all testing sessions. The reliability of the BMS has been assessed for the measurement of PPO during the BBP in a study by Alemany et al. (2). In this study, the authors reported a strong intraclass correlation coefficient (r = 0.93) for peak power obtained during the BBP.
After a test for the normality of distribution, data were expressed as the mean ± SD. Statistical analysis was carried out using a repeated-measures one-way ANOVA to determine whether PPO and maximum throw height changed throughout the testing session. When significant F values were observed (p ≤ 0.05), paired comparisons were used in conjunction with Holm's Bonferroni method for control of type I error to determine significant differences. A Pearson correlation analysis was used to assess the relationship between strength and changes in PPO after potentiation. The level of significance was set at p ≤ 0.05 in the present study, and all statistics were performed using SPSS 13.1 (SPSS Inc., Chicago, IL, USA).
Peak Power Output
A repeated-measures ANOVA revealed a significant time effect over the duration of the study (F = 29.145, partial eta2 = 0.538, p < 0 .05) with follow-up paired comparisons indicating a significant decrease in PPO in the BBP performed approximately15 seconds after the HRT compared with the baseline BBP (Figure 1A). After 4 minutes of recovery, PPO returned to a similar value to baseline with no significant difference between these 2 values (baseline: 879 ± 20 vs. 4 min: 878 ± 22 W, p > 0.05). Subjects in the present study produced their maximum PPO after 8 minutes of recovery from the HRT, and this power output was significantly higher than the power outputs at all other time points except at 12 minutes (Figure 1A). There was no significant difference between the PPO at 12, 16, 20, or 24 minutes when compared with the baseline values (Figure 1A).
The repeated-measures ANOVA revealed a significant time effect on throw height (F = 17.362, partial eta2 = 0.410, p < 0.001). Maximum throw height during the BBP was observed after 8 minutes of recovery from the HRT, and this was significantly higher when compared with throw height recorded at baseline (35.3 ± 1.4 vs. 37.2 ± 1.4 cm, p < 0.01) and at 16-, 20-, and 24-minute time points (Figure 1). There was no significant difference between the throw height at 8 minutes compared with the throw height at 12 minutes (37.2 ± 1.4 vs. 36.5 ± 1.3 cm, p > 0.05). When the players performed the BBP immediately (approximately15 s) after the HRT, their throw height was significantly reduced compared with their baseline BBP (31.7 ± 1.2 vs. 35.3 ± 1.4 cm, p < 0.01) (Figure 1B).
A significant positive correlation was found between 3RM strength and delta potentiation at the 8-minute time point (PO at 8 min - PO at baseline) (r = 0.520, p = 0.006, n = 26). Results showed that 15 (58%) subjects obtained their highest PPO at the 8-minute time point. Whereas 7 subjects obtained their peak at 12 minutes, 3 subjects achieved it at 16 minutes, and 1 subject produced his best results after only 4 minutes of recovery.
The results of the present study indicate that, on average, an 8-minute recovery is required between the HRT and subsequent BBP to observe enhanced power output in the upper body in a group of professional rugby players (Figure 1). The primary aim of the present study was to determine the recovery period required to observe enhanced power output during the BBP after a bout of HRT in a group of professional rugby players. Previous studies examining the effectiveness of HRT on subsequent explosive muscle performance have used recovery periods ranging from 0 to 18.5 minutes (3,6-8,14,20,24,30) with no uniform agreement to date on the optimal time required. The majority of the studies have used recovery periods of approximately 4 minutes, presumably to allow for PCr resynthesis after the HRT (3,6,8,30). In the present study, when we allowed 4 minutes of recovery between the HRT and the BBP, we found no significant difference between this time point and baseline, which probably reflects the replenishment of phosphocreatine (PCr) stores after the HRT (27). This finding is supported by the early findings of Gullich and Schmitbleicher (15), who found an initial depression in H-reflex activity after a preload stimulus with the H-reflex amplitude and returning to levels similar to baseline after 4 minutes of recovery.
To date, only 3 studies have directly examined the effect of varying recovery times on subsequent muscle performance (8,20,24), and all 3 of these studies examined lower-body performance with no study to date examining this in relation to upper-body performance despite the importance of upper-body power to many sports. For example, Kilduff et al. (23) examined the effects of an HRT stimulus (3 sets of 3 reps at 87% 1 repetition maximum [1RM]) of lower-body performance (countermovement jump) at various time internals (e.g., approximately 15 s and 4, 8, 12, 16, 20, and 24 min after HRT) and reported that the optimal recovery period for utilization of PAP during the lower body was 8 minutes. The results of the current study mirror the finding we have previously reported for the lower body in that 8 minutes of recovery is required to achieve maximal increases in PPO and maximum throw height in the upper body. In addition, the findings by Gullich and Schmitbleicher (15) support the current studies findings in that they reported that the greatest increase in H-reflex activity (32%) after their HRT occurred after a 8.7 ± 3.6 minute recovery period, which lead to a significant enhancement of explosive force production in plantar flexions.
There have been a limited number of studies examining the effectiveness of longer than 5 minutes of recovery between the HRT and subsequent explosive exercise (7,24). For example, Chiu et al. (7) reported that average force, average power, and peak power were significantly greater at 18.5 minutes postactivation compared with 5 minutes postactivation. However, because measurements were only taken at these time points, the optimal recovery period could be anywhere between 5 and 18.5 minutes. The results of the current study help clarify the recovery period needed to achieve maximal increases in BBP performance in well-trained athletes. Our results indicate that 8 minutes of recovery is required to achieve maximal increases in PPO and maximum throw height. However, we did observe some individual variation, with 15 (58%) subjects performing their best BBP at the 8-minute time point and the remaining 42% performing better at the 4-minute (1 subject), 12-minute (7 subjects), and 16-minute (3 subjects) time points. This finding supports the recommendation of Comyns et al. (8) that individual determination of the optimal recovery rest interval may be necessary.
Because electromyography recordings were not obtained in this study, we can only speculate on the potential mechanism for the observed improvement in performance after PAP. However, 2 primary theories have been proposed to date: (a) the preload stimulus acts to enhance motor-unit excitability, possibly affecting a number of processes such as increased motor unit recruitment, increased motor unit synchronization, decreased presynaptic inhibition, or greater central input to the motor neuron; and (b) enhanced phosphorylation of the myosin light chain (MLC) occurs, in which the preload causes an increase in sarcoplasmic Ca2+, which activities MLC kinase and which in turn increases actin-myosin cross-bridging (16).
Despite the majority of PAP studies showing an ergogenic effect on performance (3,13), there are still a significant number of studies that report no ergogenic effect (6). As indicated in the review by Hodgson et al. (16), training history or strength levels of the subjects appear to be important factors in the outcome of PAP studies. Studies to date have used subjects of varying strength levels (from recreationally trained to power athletes), and in some studies, it was only when subjects were differentiated into “strong” and “weak” subjects based on their strength levels (3) or training experience (7) that a performance effect was observed. For example, Chiu et al. (7) initially reported no change in performance after a preload stimulus when the group were considered as a whole; however, once the group was divided on the basis of strength, performance increases were observed. In support of this, the studies by Young et al. (30) and Duthie et al. (11) found significant correlations between performance changes after the preload stimulus and measures of strength (e.g., 1RM) (r = 0.73 and r = 0.66, respectively), which indicated that stronger subjects had greater potential for performance gains after HRT. Results from the present study also show a positive correlation between the subjects' strength (3RM) level and the change in performance after potentiation (r = 0.520, p = 0.006). This relationship suggests that stronger individuals have greater potential to increase BBP performance. Although the exact reason behind this relationship between strength and potentiation remains unclear, it has been demonstrated that resistance trained athletes have greater activation of the musculature involved during HRT, which would affect the H-reflex and myosin regulatory light chain phosphorylation, the 2 mechanisms involved in the PAP phenomenon (1). In addition, Gullich and Schmitbleicher (15) reported differences between speed-strength athletes (highly trained) and sports students (trained), in that the highly trained athletes showed a significantly higher and longer lasting potentiation effect compared with the less-trained sports students. In addition, this study reported differences between the level of potentiation between the soleus muscle (predominantly slow-twitch muscle fiber) and the gastronomies muscle (predominantly fast-twitch muscle fiber), with the gastronomies muscle having a greater level and longer-lasting potentiation effect compared with the soleus muscle.
Despite the present study showing a positive effect of PAP on BBP in our group of professional rugby players, it is still to be determined whether PAP can be harnessed to improve power production in the more complex tasks involved in rugby such as sprinting, tackling, and scrummaging. In addition, individual determination of the optimal recovery time required for enhanced performance after HRT is required and is supported by the findings of Gullich and Schmitbleicher (15), who reported the time course of the athlete's highest reflex response showed considerable interindividual variation.
In conclusion, the results from the present study indicate that muscle performance (e.g., power) is enhanced after HRT in the upper body providing adequate recovery is given between the 2 activities. In addition, the athlete's initial strength level plays in important role in their ability to use this PAP phenomenon.
The current findings indicate that between 8 and 12 minutes of recovery is required between the HRT and the explosive activity to obtain the greatest benefit in upper-body performance. However, the present findings also highlights the need for individual determination of the optimal recovery time required for enhanced performance.
1. Aagaard, P, Simonsen, EB, Andersen, JL, Magnusson, P, and Dyhre-Poulsen, P. Neural adaptation to resistance training: changes in evoked V-waves and H-reflex responses. J Appl Physiol
92: 2309-2328, 2002.
2. Alemany, JA, Pandorf, CE, Montain, SJ, Castellani, JW, Tuckow, AP, and Nindl, BC. Reliability assessment of ballistic jump squats and bench throws. J Strength Cond Res
19: 33-38, 2005.
3. Baker, D. Acute effects of alternating heavy and light resistances on power output during upper-body complex power training. J Strength Cond Res
17: 493-497, 2003.
4. Baker, D, Nance, S, and Moore, M. The load that maximizes the average mechanical power output during explosive bench press throws in highly trained athletes. J Strength Cond Res
15: 20-24, 2001.
5. Baker, D and Newton, RU. Acute effect on power output of alternating an agonist and antagonist muscle exercise during complex training. J Strength Cond Res
19: 202-205, 2005.
6. Brandenburg, JP. The acute effects of prior dynamic resistance exercise using different loads on subsequent upper-body explosive performance in resistance-trained men. J Strength Cond Res
19: 427-432, 2005.
7. Chiu, LZ, Fry, AC, Weiss, LW, Schilling, BK, Brown, LE, and Smith, SL. Postactivation potentiation response in athletic and recreationally trained individuals. J Strength Cond Res
17: 671-677, 2003.
8. Comyns, TM, Harrison, AJ, Hennessy, LK, and Jensen, RL. The optimal complex training rest interval for athletes from anaerobic sports. J Strength Cond Res
20: 471-476, 2006.
9. Deutsch, MU, Kearney, GA, and Rehrer, NJ. Time-motion analysis of professional rugby union players during match-play. J Sports Sci
25: 461-72, 2007.
10. Duthie, G, Payne, D, and Hooper, S. Time motion analysis of 2001 and 2002 super 12 rugby. J Sports Sci
23: 523-530, 2005.
11. Duthie, G, Young, WB, and Aitken, DA. The acute effects of heavy loads on jump squat performance: An evaluation of the complex and contrast methods of power development. J Strength Cond Res
16: 530-538, 2002.
12. Ebben, WP, Jensen, RL, and Blackard, DO. Electromyographic and kinetic analysis of complex training variables. J Strength Cond Res
14: 451-456, 2000.
13. Gosseen, ER and Sale, DG. Effect of postactivation potentiation on dynamic knee extension performance. Eur J Appl Physiol
83: 524-530, 2000.
14. Gourgoulis, V, Aggeloussis, N, Kasimatis, P, Mavromatic, G, and Garas, A. Effect of a submaximal half-squats warm-up program on vertical jumping ability. J Strength Cond Res
17: 342-344, 2003.
15. Gullich, A and Schmidtbleicher, D. Short-term potentiation of power performance induced by maximal voluntary contractions. In: Proceedings of the XVth Congress of the International Society of Biomechanics
, 1996. pp. 348-349.
16. Hodgson, M, Dochery, D, and Robbins, D. Post-activation potentiation. Sports Med
35: 585-595, 2005.
17. Hrysomallis, C and Kidgell, D. Effect of heavy dynamic resistive exercise on acute upper-body power. J Strength Cond Res
15: 426-430, 2001.
18. International Powerlifting Federation. Technical Rules Book of International Powerlifting Federation
. Available at: http://www.powerlifting-ipf.com/IPF_rulebook.pdf
. 2002. Accessed July 2008.
19. Izquierdo, M, Hakkinen, K, Gonzalez-Badillo, JJ, Ibanez, J, and Gorostiaga, EM. Effects of long-term training specificity on maximal strength and power of the upper and lower extremities in athletes from different sports. Eur J Appl Physiol
87: 264-271, 2002.
20. Jessen, RL and Ebben, WP. Kinetic analysis of complex training rest interval effect on vertical jump performance. J Strength Cond Res
17: 345-349, 2003.
21. Jones, P and Lees, A. A biomechanical analysis of the acute effects of complex training using lower limb exercises. J Strength Cond Res
17: 694-700, 2003.
22. Kawamori, N, Crum, AJ, Blumert, PA, Kulik, JR, Childers, JT, Wood, JA, Stone, MH, and Haff, G. Influence of difference relative intensities on power output during the hang power clean: identification of the optimal load. J Strength Cond Res
19: 698-706, 2005.
23. Kilduff, LP, Bevan, H, Owen, N, Kingsley, MI, Bunce, P, Bennett, M, and Cunningham, D. Optimal loading for peak power output during the hang power clean in professional rugby players. Int J Sports Physiol Perf
2: 260-269, 2007.
24. Kilduff, LP, Owen, N, Bevan, H, Bennett, M, Kingsley, MI, and Cunningham, D. Influence of recovery time on postactivation potentiation in professional rugby players. J Sports Sci
. 26: 795-802, 2008.
25. Rassier, DE and MacIntosh, BR Coexistence of potentiation and fatigue in skeletal muscle. Braz J Med Biol Res
33: 499-508, 2000.
26. Stone, MH, O'Bryant, HS, McCoy, L, Coglianese, R, Lehmkuhl, M, and Shilling, B. Power and maximal strength relationships during performance of dynamic and static weighted jumps. J Strength Cond Res
17: 140-147, 2003.
27. Nevill, AM, Jones, DA, Mcintyre, D, Bogdanis, GC, and Nevill, ME. A model for phosphocreatine resynthesis. J Appl Physiol
82: 329-335, 1997.
28. Newton, RU, Murphy, AJ, Humphries, BJ, Wilson, GJ, Kraemer, WJ, and Hakkinen, K. Influence of load and stretch shortening cycle on the kinematics, kinetics and muscle activation that occurs during explosive upper-body movements. Eur J Appl Physiol
75: 333-342, 1997.
29. Wilson, GJ. Newton, RU, Murphy, AJ, and Humphries, BJ.AJ, and Humphries, BJ. The optimal training load for the development of dynamic athletic performance. Med Sci Sports Exerc
25: 1279-1286, 1993.
30. Young, WB, Jenner, A, and Griffiths, K. Acute enhancement of power performance from heavy load squats. J Strength Cond Res
12: 82-84, 1998.