Rugby league is a high-intensity intermittent team sport played over 80 minutes. The game is combative in nature and is characterized by its forceful collisions (9); hence, the associated muscular trauma and damage is substantial. The rate and quality of recovery from rugby league is therefore considered imperative. Athlete recovery after training and competition is multifactorial and typically dependent on both the nature of the exercise performed and a combination of external factors (1,3,16) including the type of fatigue, current levels of training and nontraining stress, and capacity to cope with the stressors (1). Only a handful of studies have examined the efficacy of recovery modalities and their ability to promote recovery from muscular damage and trauma after contact sport (10,12,21). One such modality is hydrotherapy. Hydrotherapy procedures are increasing in popularity and becoming a common component of athlete recovery routines after contact sport competition (23). The physiological response to immersion in varying temperatures is well investigated and understood (4,5), but research investigating the use of hydrotherapy modalities such as cold water immersion (CWI) and contrast water therapy (CWT) on the recovery of physiological and performance measures after contact sport, specifically the rugby codes, is limited and equivocal in terms of recovery efficacy. Performing CWI after rugby union matches was shown to have a negative recovery effect (12); however, the use of CWT postmatch has been shown to improve the recovery of measures such as creatine kinase (CK) (10) and anaerobic performance (12). In comparison, CWT did not significantly enhance vertical jump and muscle soreness recovery after Australian rules football matches (8).
The implementation of light aerobic exercise as active recovery (ACT) is commonly practiced after contact sport (10). Although the physiological benefits of completing ACT are well known, research on the efficacy of ACT after rugby is equivocal and is limited to the use of CK and perceptual muscle soreness (PMS) as postgame recovery markers (10,21). Active recovery has been used postmatch in contact sport with conflicting findings. It was reported that ACT had a beneficial recovery effect on postmatch CK up to 84 hours after a professional rugby match (10). In contrast, ACT was reported to have no beneficial recovery effect on CK, although an increase in perceptual psychological state was observed after an 80-minute rugby match (21). Given the limitations and conflicting results in the research to date, the purpose of this study was to quantify the relative efficacy of ACT, CWI, and CWT recovery modalities after professional rugby league matches, while accounting for relative match workloads.
Experimental Approach to the Problem
Subjects were monitored across 3 National Rugby League (NRL) competition matches. Within 1 hour after each match, all subjects performed 1 of 3 selected recovery modalities (CWI, CWT, or ACT) (2). Measures of neuromuscular performance (countermovement jump [CMJ] height), PMS, and muscle damage (CK) were assessed at 24 hours prematch, and 1, 18, and 42 hours postmatch. No training, activity, or other recovery modalities were scheduled or performed by subjects within the 42-hour monitoring period to assess the true recovery effect of each modality being investigated. Individual subject match statistics were analyzed to produce a quantification of overall match intensity and workload.
Twenty-one professional rugby league players from the NRL New Zealand Warriors rugby league squad volunteered to participate in this study. Their age, mass, and height were 23.5 ± 2.6 years, 97.3 ± 8.7 kg, and 183.8 ± 8.8 cm (mean ± SD). The Auckland University of Technology Ethics Committee approved all procedures, and all subjects provided signed informed consent.
All 3 recovery interventions were administered over 3 consecutive home games (over 6 weeks) in a randomized order during the NRL competition. The subjects were given an opportunity to familiarize themselves with all testing and recovery procedures before the investigation.
Cold Water Immersion
Subjects immersed their lower body in a stationary position to the level of the anterior superior iliac spine in a water temperature range of 10–12° C for 5 minutes, as reported previously (12), before carrying out their normal postmatch routine (rehydrating, showering, media interviews, club promotions). No other recovery modality or physical activity was performed within the 42-hour postgame monitoring time period.
Contrast Water Therapy
Subjects immersed their body in a stationary position to the level of the anterior superior iliac spine in 1 of 2 temperature-controlled water baths, alternating between 1 minute in cold water (8–10° C) and 2 minutes in hot water (40–42° C) for 3 rotations, as reported previously (10). The normal postmatch routine (rehydrating, showering, media interviews, club promotions) was completed thereafter. No other recovery modality or physical activity was performed within the 42-hour postgame monitoring time period.
Subjects completed low-intensity exercise on a cycle ergometer (Life Fitness, Schiller Park, IL, USA) for 7 minutes (80–90 rpm, 150 W) in an allocated recovery area after the match (10). The normal postmatch routine (rehydrating, showering, media interviews, club promotions) was completed thereafter. A 7-minute duration was selected because it was considered to be a sufficient time frame to increase blood flow and enhance the clearance of metabolites (10). Time and resource limitations were also factors influencing ACT duration (10). No other recovery modality or physical activity was performed within the 42-hour postame monitoring time period.
All recovery markers described in the following were measured 24 hours prematch, and 1, 18, and 42 hours postmatch.
Creatine Kinase Sampling and Analysis
Trained phlebotomists collected all blood samples. Venous blood samples (5 ml) were collected from the subject’s antecubital area using a heparinized plasma Vacutainer tube and syringe set (Becton, Dickinson and Company, San Diego, CA, USA). Blood samples were immediately prepared via centrifugation in preparation for analysis of total CK activity. All blood samples were stored in −20 °C and analyzed within 24 hours of the sample being taken.
Neuromuscular Performance (Countermovement Jump Height)
Subjects performed 3 singular CMJs using a Ballistic Measurement System (Fitness Technology, Adelaide, Australia) contact mat and software package. The subjects started with both feet on the contact mat with their hands on their hips to eliminate the influence of arm swing on CMJ performance (6,18). Subjects were instructed to lower as quickly as possible at a self-selected depth and then jump as high as possible in the ensuing concentric phase. Subjects were also instructed to take off from the contact mat with their knees and ankles extended and land in a similarly extended position (7). Intraday (coefficient of variation = 5.2%) and interday (coefficient of variation = 5.0%) jump height (JH) reliability has been reported previously for the CMJ (6).
Perceived Muscle Soreness Ratings
To assess each subject’s PMS, subjects were requested to provide a rating (Table 1) ranging from 1 (extreme soreness) to 5 (no soreness). Subjects were also asked to identify any injuries they sustained during the competition match that may have had an effect on any of the dependent variables.
Fatigue Scale (Contact)
To assist in the quantification of match intensity and severity for each subject, a contact fatigue scale was developed. This included the use of specific match statistics being divided into categories and allocated a number, which was representative of the amount of work and contact that each player was exposed to for each match statistic. Match statistics included in the fatigue factor (Table 2) were total tackle contact made (tackles completed and missed), total hit-ups (an attacking tactic where a player receives a pass at pace and runs directly at the opposition’s defensive line making contact with ≧1 defenders), and rate of perceived exertion. Rate of perceived exertion was included in the contact fatigue scale because the contact area of the game is considered to be the most physically demanding aspect of contact sport (9,22). The final fatigue score was calculated as the sum of the total tackles made, total hit-ups made, and rate of perceived exertion as detailed in Table 2.
Recovery effects were analyzed with mixed modeling to account for any nonuniformity arising from individual responses. Separate analyses were performed for the dependent variables JH, PMS, and CK. Jump height and CK were analyzed after log transformation to reduce nonuniformity of effects and errors over the range of values of the dependent variable; effects and errors with these variables were expressed as percents via back-transformation. The mean effects of the treatments and the mean changes between treatments were estimated with a fixed effect, the interaction of treatment with time. A covariate (contact fatigue score) interaction with time was included to estimate and adjust for the effect of within-subject changes in the intensity of each match on the postmatch values of the dependent variable; for this purpose, the value of the covariate was rescaled to give a mean of zero for each subject, and the within-subject SD was rescaled to allow estimation and interpretation of the effect of 2 mean within-subject SD of the covariate. The random effects in the mixed model were the identity of the player, the residual error representing within-subject variation from time point to time point, and terms representing additional within-subject variation for each treatment and postmatch time point. Mean values and SDs are used throughout as measures of centrality and spread of data. Standardization of effects (dividing the effects by a between-subject SD) was used to make magnitude-based inferences about the outcomes. The SD used for standardization was derived from the random effects in the mixed model and is effectively the SD at the prematch time point. Standardization for effects with JH and CK was performed with the log-transformed values of these variables. Magnitude of all standardized effects was evaluated with a modification of Cohen’s scale for thresholds of effects: <0.2, trivial; 0.2–0.6, small; 0.6–1.2, moderate; and >1.2, large (14). To make clinical inferences about true values of effects in the population, the uncertainties in the effects were expressed as probabilities of harm or benefit in relation to the smallest worthwhile effect (±0.2). The effects of the treatments were unclear if there was too much risk of harm compared with the chance of benefit (odds ratio of benefit to harm <66, equivalent to >0.5% risk of harm and >25% chance of benefit). All other effects were evaluated probabilistically to communicate the chance of the effect being trivial, beneficial, or harmful with the following scale: 25–75%, possibly; 75–95%, likely; 95–99.5%, very likely; and >99.5%, most likely (13).
Percent differences in JH and CK pre- to all postmatch time points along with raw score changes for PMS for all 3 recovery modalities with confidence limits and a qualitative inference of the magnitude of the difference are detailed in Table 3. The postmatch percent changes for JH performance relative to baseline at each postgame time point can be observed in Figure 1, raw score changes for PMS relative to baseline in Figure 2, and CK percent change relative to baseline in Figure 3 in relation to all 3 recovery modalities. Note that the covariate (contact fatigue score) was included to estimate and adjust for the effect of within-subject changes in the intensity of each match on the postmatch values of the dependent variable of interest.
Contrast water therapy is likely to have clear beneficial recovery effects on JH performance 1–18 and 18–42 hours postmatch as compared with ACT, whereas CWI was beneficial to recovery effects at 18–42 hours postmatch only. Contrast water therapy is very likely to be effective in regenerating JH performance at 1–18 hours postmatch as compared with CWI (Table 3 and Figure 1).
Both CWI and CWT reduced PMS to a meaningfully greater level than ACT at 18–42 hours postmatch, whereas CWI was found to be more effective than ACT at 1–18 hours postmatch. At 18–42 hours postmatch, CWT is likely to have clear recovery benefits on PMS as compared with CWI, which was considered a possibly beneficial difference (Table 3 and Figure 2).
Contrast water therapy, as compared with ACT, is likely to have clear beneficial recovery effects on CK at 1–18 and 18–42 hours postmatch, whereas CWI will possibly provide beneficial recovery effects on CK at 18–42 hours postmatch only. The use of CWT is likely to have a more beneficial recovery effect in reducing CK compared with CWI at 1–18 and 18–42 hours postmatch (Table 3 and Figure 3).
The reader should be aware of the limitations of this study while reading the subsequent discussion. First, the recovery modalities were not randomly crossed over for each subject but instead each recovery modality was performed after 3 separate games owing to equipment and facility restrictions and practicality. Nonetheless, given the propensity of practitioners to use recovery modalities dependent on facility and equipment availability, investigation of such postgame recovery modalities accounting for covariates such as game intensity is of value. Second, it should be noted that the subject group used in this study was the entire available group from the target population, that is, the top training squad of an elite rugby league team. Increasing subject numbers by including subjects other than the elite training squad with the intention of providing greater statistical power would have compromised the validity of the study in terms of extrapolating findings to other similar athletes (11). Third, the recovery modalities used in the current study were used independently from one another; therefore, there is a possibility that a combination of recovery modalities both immediately and 1 day postgame and greater exposure times may further enhance the recovery response after professional rugby league matches. Finally, it was considered unethical to include a passive recovery modality as a control when using professional athletes as subjects; hence, the ACT was considered our control.
Our key finding was that both CWT and CWI were clearly effective recovery modalities 42 hours after a game of rugby league as compared with ACT alone, although the trend was for CWT to be the most effective recovery modality of the two. Gill et al. (10) and Higgins et al. (12) also found CWT to be an effective recovery modality after contact sport; however, Dawson et al. (8) concluded that recovery of muscle soreness, vertical jump, and power at 48 hours postgame was not significantly enhanced by performing an immediate CWT postgame recovery. The contrasting results between our study and that of Dawson et al. (8) may be owing to the different technique used to expose subjects to alternating water temperatures. Dawson et al. (8) employed the use of showers as the means for heat exposure compared with the use of baths for CWT in our study. It may be that the effect of hydrostatic pressure from actual water immersion versus superficial localized water contact is of influence. The protocol of Gill et al. (10) was similar to this study incorporating water immersion to the level of the anterior superior iliac spine. Higgins et al. (12) also applied waist-deep immersion (using a different protocol) after a rugby match, further supporting that water immersion in conjunction with alternating temperatures is of benefit to enhancing recovery after contact sport. It is possible that the relative superiority of CWT compared with CWI was owing to total hydrostatic time exposure (CWT 9 minutes; CWI 5 minutes). Future studies may benefit from equating hydrostatic time exposure between CWT and CWI modalities to quantify such an effect.
Cold water immersion clearly recovered JH performance, PMS, and muscle damage by 42 hours postgame when compared with ACT in our study. Higgins et al. (12) also implemented a 5-minute CWI protocol; however, small and medium negative effects on anaerobic performance after a rugby competition match were reported. It was also concluded that CWI increased perceived feeling of muscular tightness and elicited a generally negative response compared with CWT. Notably, only anaerobic performance measures were used; no direct physiological or functional performance (e.g., jumps) markers were investigated to identify the underlying mechanisms associated with this particular protocol. Studies by Rowsell et al. (19,20) investigated the effect of CWI and thermoneutral water immersion during and after a 4-day soccer tournament (1 game each day) and reported a reduction in leg soreness perception, similar to our findings. However, Rowsell et al. (19) also reported no significant improvement in JH or reduction in muscle damage after the use of CWI, in contrast to our findings. In our study, CWI was performed once only after the match, with all recovery markers being monitored up to 42 hours after 1 match. Rowsell et al. (19) used CWI after each game and monitored recovery markers 22 hours postgame over 4 consecutive games in as many days and observed no difference in markers from days 1 to 5. It may be that allowing only 22 hours postgame for CWI to be effective on the recovery markers was of insufficient duration. Although the current literature on the efficacy of CWI after team contact sport is unclear (12,15), the current study provides evidence that CWI assists in the recovery of JH performance, PMS, and damage within a time frame typically associated with commencement of structured training sessions after a competition match.
In the present study, ACT was not clearly effective in recovering JH, PMS, and CK by 42 hours after professional rugby league games compared with CWI and CWT. In contrast, Gill et al. (10) found that ACT elicited a similar CK recovery rate to CWT at 36 and 84 hours after a competitive rugby game. Suzuki et al. (21) also reported no difference in CK activity as a result of ACT or passive recovery modalities, although an increase in perceptual psychological state was observed after an 80-minute rugby match. However, the study by Suzuki et al. (21) incorporated a different means of ACT (multidirectional movements and swimming in water) and was performed for an hour each day for 2 days postmatch, whereas in the current study ACT was performed for only 7 minutes and immediately postmatch only. Previous researchers have suggested that the increased energy demands of higher volume or intensity ACT may compromise its efficacy (17). Hence, the high volume of each ACT session employed by Suzuki et al. (21) may explain why no physiological benefit was observed. In the present study, the ACT modality was not as effective in enhancing any of our recovery markers when compared with CWT. Gill et al. (10) incorporated the same ACT protocol as ours after professional rugby union matches, finding that ACT postmatch was as effective on recovery as CWT and compression garment modalities at any postmatch time point, a result difficult to explain when compared with our findings. Although it has been contested that the implementation of ACT provides theoretically similar physiological benefits to CWT (24), according to our study CWT is superior to ACT as a recovery modality.
It is common in professional rugby league that the first training session of a training week during the competitive season is conducted within a 36- to 42-hour postmatch time period. Both CWI and CWT were clearly effective in improving JH performance, PMS, and CK by 42 hours compared with ACT. Allowing sufficient time for the body to recover after a game characterized by a high number of collisions is critical. It is acknowledged that if we used time points longer than 42 hours postmatch, a greater recovery effect may have been observed.
Literature concerning the postexercise use of various recovery modalities and their subsequent recovery effect on physiological markers is well documented, but very few studies have examined the efficacy of recovery modalities and their ability to promote recovery after contact sport. No studies have attempted to incorporate match statistics to quantify match intensity and severity and its subsequent recovery effect on performance and physiological markers. We found that both CWT and CWI were clearly effective recovery modalities 42 hours after a game of rugby league as compared with ACT alone; however, the trend was for CWT to be the most effective recovery modality of the two. Future research on contact sport (specifically rugby codes) recovery should further examine the relative efficacy of recovery modalities by quantifying match intensity and severity to determine recovery effects on postmatch physiological and performance markers. Investigations examining the recovery benefit of different exposure times, number of rotations (CWT), equated hydrostatic pressure exposure, and the use of a combination of recovery modalities after contact sport would give coaches and practitioners the ability to make better informed decisions regarding recovery modality prescription. The use of the CWT protocol used in this study to recover JH performance, reduce muscle damage, and improve PMS leading into the first structured training session after rugby league is recommended: hot water immersion for 2 minutes (40–42° C) followed by 1 minute of CWI (8–10° C) to the level of the anterior superior iliac spine repeated 3 times consecutively. Practically available resources often limit the choice of recovery modality implemented in the field. Specifically, when traveling away from home, resources and space restrictions may limit the ability to implement the procedures and protocols compared with home recovery procedures. Practical implementation of CWT is possible using accessible resources such as portable baths or bins filled with ice. Even though CWT was clearly more effective by 42 hours postgame than CWI in the current study, the use of CWI was still effective in reducing muscular damage and soreness, and recovering muscular performance. If circumstances arise where CWT is not practically available, rather than neglecting recovery, CWI (arguably a simpler modality to implement) will provide a similar recovery effect after contact sport. However, we recommend the use of the CWT protocol used in this study to recover JH performance, reduce muscle damage, and improve PMS leading into the first structured training session after elite rugby league competition matches.
The authors thank Dayne Norton of the New Zealand Warriors Rugby League club for his assistance in the organization and implementation of the performance testing for this study. The authors also thank the New Zealand Warriors Rugby League club for providing access to the players. Lastly, the authors thank Prof. Will Hopkins for his expertise and assistance in the formulation of the statistical analysis for this study. No funding was received for this study and no conflict of interest occurred.
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Keywords:Copyright © 2013 by the National Strength & Conditioning Association.
hydrotherapy; active recovery; creatine kinase; jump height