Season-long increases in perceived muscle soreness in professional rugby league players: role of player position, match characteristics and playing surface

A four-season study quantifying the weekly external training loads during different between match microcycle lengths in professional rugby league

This study investigated differences in external training load between microcycle lengths and its variation between microcycles, players, and head coaches. Commonly used external training load variables including total-, high-speed- (5-7 m∙s-1), and sprint-distance (> 7 m∙s-1) alongside combined high acceleration and deceleration distance (> 2 m∙s-2). Which were also expressed relative to time were collected using microtechnology within a repeated measures design from 54 male rugby league players from one Super League team over four seasons. 4337 individual observations across ninety-one separate microcycles and six individual microcycle lengths (5 to 10 day) were included. Linear mixed effects models established the differences in training load between microcycle-length and the variation between-microcycles, players and head coaches. The largest magnitude of difference in training load was seen when comparing 5-day with 9-day (ES = 0.31 to 0.53) and 10-day (ES = 0.19 to 0.66) microcycles. The greatest number of differences between microcycles were observed in high- (ES = 0.3 to 0.53) and sprint-speed (ES = 0.2 to 0.42) variables. Between-microcycle variability ranged between 11% to 35% dependent on training load variable. Training load also varied between players (5-65%) and head coaches (6-20%) with most variability existing within high-speed (19-43%) and sprinting (19-65%). Overall, differences in training load between microcycle lengths exist, likely due to manipulation of session duration. Furthermore, training load varies between microcycle, player and head coach.

Quantifying Fatigue in the Rugby Codes: The Interplay Between Collision Characteristics and Neuromuscular Performance, Biochemical Measures, and Self-Reported Assessments of Fatigue

Locomotor and collision actions that rugby players complete during match-play often lead to substantial fatigue, and in turn, delays in recovery. The methods used to quantify post-match fatigue and recovery can be categorised as subjective and objective, with match-related collision characteristics thought to have a primary role in modulating these recovery measures. The aim of this review was to (1) evaluate how post-match recovery has been quantified in the rugby football codes (i.e., rugby league, rugby union, and rugby sevens), (2) to explore the time-course of commonly used measures of fatigue post-match, and (3) to investigate the relationships between game-related collisions and fatigue metrics. The available evidence suggests that upper-, and lower-body neuromuscular performance are negatively affected, and biomarkers of muscular damage and inflammation increase in the hours and days following match-play, with the largest differences being at 12–36 h post-match. The magnitude of such responses varies within and between neuromuscular performance (Δ ≤ 36%, n = 13 studies) and tissue biomarker (Δ ≤ 585%, n = 18 studies) measures, but nevertheless appears strongly related to collision frequency and intensity. Likewise, the increase in perceived soreness in the hours and days post-match strongly correlate to collision characteristics across the rugby football codes. Within these findings, there are specific differences in positional groups and recovery trajectories between the codes which relate to athlete characteristics, and/or locomotor and collision characteristics. Finally, based on these findings, we offer a conceptual model of fatigue which details the multidimensional latent structure of the load to fatigue relationship contextualised to rugby. Research to date has been limited to univariate associations to explore relationships between collision characteristics and recovery, and multivariate methods are necessary and recommended to account for the latent structures of match-play external load and post-match fatigue constructs. Practitioners should be aware of the typical time windows of fatigue recovery and utilise both subjective and objective metrics to holistically quantify post-match recovery in rugby.

Quantification of training load distribution in mixed martial arts athletes: A lack of periodisation and load management

The aim of this study was to quantify typical training load and periodisation practices of MMA athletes. MMA competitors (n = 14; age = 22.4 ± 4.4 years; body mass = 71.3 ± 7.7 kg; stature = 171 ±9.9 cm) were observed during training for 8 consecutive weeks without intervention. Seven athletes were training for competitive bouts whilst the remaining 7 were not. Daily training duration, intensity (RPE), load (sRPE and segRPE), fatigue (short questionnaire of fatigue) and body region soreness (CR10 scale) were recorded. Using Bayesian analyses (BF₁₀≥3), data demonstrate that training duration (weekly mean range = 3.9–5.3 hours), sRPE (weekly mean range = 1,287–1,791 AU), strain (weekly mean range = 1,143–1,819 AU), monotony (weekly mean range = 0.63–0.83 AU), fatigue (weekly mean range = 16–20 AU) and soreness did not change within or between weeks. Between weeks monotony (2.3 ± 0.7 AU) supported little variance in weekly training load. There were no differences in any variable between participants who competed and those who did not with the except of the final week before the bout, where an abrupt step taper occurred leading to no between group differences in fatigue. Training intensity distribution corresponding to high, moderate and low was 20, 33 and 47%, respectively. Striking drills accounted for the largest portion of weekly training time (20–32%), with MMA sparring the least (2–7%). Only striking sparring and wrestling sparring displayed statistical weekly differences in duration or load. Athletes reported MMA sparring and wrestling sparring as high intensity (RPE≥7), BJJ sparring, striking sparring and wrestling drills as moderate intensity (RPE 5–6), and striking drills and BJJ drills as low intensity (RPE≤4). We conclude that periodisation of training load was largely absent in this cohort of MMA athletes, as is the case within and between weekly microcycles.

Identifying Contextual Influences on Training Load: An Example in Professional Rugby Union

ABSTRACT

Dalton-Barron, NE, McLaren, SJ, Black, CJ, Gray, M, Jones, B, and Roe, G. Identifying contextual influences on training load: an example in professional rugby union. J Strength Cond Res 35(2): 503-511, 2021-We aimed to investigate the contextual factors influencing training load (TL), as determined by session rating of perceived exertion (sRPE-TL), accumulated within a match-to-match microcycle in rugby union players. Session rating of perceived exertion-TL data were collected daily from 35 professional rugby union players from the same team in the English Championship over the course of an in-season period. Players were split by positional groups (backs and forwards) and sRPE-TL data were categorized as: field-based on-feet sRPE-TL (sRPEField-TL), gym-based sRPE-TL (sRPEGym-TL), and the total summation of both (sRPETotal-TL). Three 2-level linear mixed models were built for each dependent variable in each positional group, with magnitude-based inferences applied. Long between-match recovery cycles (≥7 days) resulted in very likely to almost certainly small to moderate increases in sRPE-TL for all modalities and positions (fixed effect [mean range] = 28.5%-42.0%), apart from sRPEField-TL for forwards. For backs, there was a very likely small decrease in sRPEField-TL as the season progressed (-16.7% per trimester). Losing the last league match was associated with very likely and almost certainly small decreases in sRPETotal-TL and sRPEGym-TL for backs (-20.7% and -36.4%, respectively). Losing the last match in any competition resulted in a very likely small increase in sRPEField-TL (21.2%) and a possibly small decrease sRPEGym-TL (-18.5%) for backs-with a likely smaller sRPEGym-TL for forwards (-33.4%). The strength of the upcoming opposition had no effect on sRPE-TL. Our findings highlight some of the multifactorial contextual factors that must be considered when planning and evaluating training microcycles.

Profiling the Post-match Recovery Response in Male Rugby: A Systematic Review

Aben, HGJ, Hills, SP, Cooke, CB, Davis, D, Jones, B, and Russell, M. Profiling the post-match recovery response in male rugby: A systematic review. J Strength Cond Res XX(X): 000-000, 2020-To minimize underperformance, injury, and illness, and to enhance readiness for training and match-play, post-match responses are commonly monitored within professional rugby. As no clear consensus exists regarding the magnitude and duration of post-match recovery, this review summarized the literature (17 studies yielded from literature searching/screening) reporting neuromuscular (countermovement jump [CMJ], peak power output [PP], and flight time [FT]), biochemical (creatine kinase [CK]) or endocrine (cortisol [C] and testosterone [T] concentrations), and subjective (wellness questionnaire and muscle soreness) indices after rugby match-play. For neuromuscular responses (11 studies), reductions in PP <31.5% occurred <30 minutes after match, returning to baseline within 48-72 hours. Post-match reductions in FT of <4% recovered after 48 hours. For biochemical and endocrine responses (14 studies), increases in CK, ranging from 120 to 451%, peaked between 12 and 24 hours, returning to baseline within 72 hours of match-play. Initial increases of <298% in C and reductions in T concentrations (<44%) returned to pre-match values within 48-72 hours. Mood disturbances (6 studies) required 48-72 hours to normalize after peak decrements of <65% at 24 hours. This review highlights that 72 hours were needed to restore perturbations in neuromuscular, biochemical and endocrine, and subjective/perceptual responses after competitive rugby match-play. Notably, only 4 studies reported responses in more ecologically valid scenarios (i.e., those in which regular training and recovery strategies were used) while also reporting detailed match demands. A lack of research focusing on youth players was also evident, as only 3 studies profiled post-match responses in younger athletes. Deeper insight regarding post-match responses in ecologically valid scenarios is therefore required.

High Prevalence of Cannabidiol Use Within Male Professional Rugby Union and League Players: A Quest for Pain Relief and Enhanced Recovery

Rugby is characterized by frequent high-intensity collisions, resulting in muscle soreness. Players consequently seek strategies to reduce soreness and accelerate recovery, with an emerging method being cannabidiol (CBD), despite anti-doping risks. The prevalence and rationale for CBD use in rugby has not been explored; therefore, we recruited professional male players to complete a survey on CBD. Goodness of fit chi-square (χ2) was used to assess CBD use between codes and player position. Effects of age on use were determined using χ2 tests of independence. Twenty-five teams provided 517 player responses. While the majority of players had never used CBD (p < .001, V = 0.24), 26% had either used it (18%) or were still using it (8%). Significantly more CBD use was observed in rugby union compared with rugby league (p = .004, V = 0.13), but player position was not a factor (p = .760, V = 0.013). CBD use increased with players’ age (p < .001, V = 0.28), with mean use reaching 41% in the players aged 28 years and older category (p < .0001). The players using CBD primarily used the Internet (73%) or another teammate (61%) to obtain information, with only 16% consulting a nutritionist. The main reasons for CBD use were improving recovery/pain (80%) and sleep (78%), with 68% of players reporting a perceived benefit. These data highlight the need for immediate education on the risks of CBD, as well as the need to explore the claims regarding pain and sleep.

Montmorency tart cherry juice does not reduce markers of muscle soreness, function and inflammation following professional male rugby League match-play

Rugby League (RL) match-play causes muscle damage, inflammation and symptoms of fatigue. To facilitate recovery, nutritional interventions are often employed, including Montmorency cherry juice (MC). We assessed the effects of MC on recovery following RL match-play in eleven male professional RL players who played in two matches (7-days apart) with MC or placebo (PLB) supplemented for 5-days pre-match, matchday and 2-days post-match. Blood was collected 48h pre-match, half-time, within 30-mins of full-time and 48h post-match to assess Interleukin concentrations (IL-6, -8 -10). Self-reported sleep, fatigue, mood, stress, and muscle-soreness were assessed 24h pre and 24 and 48h post-matches with muscle function assessed 48h pre and 48h post-match. No differences in distance covered (6334 ± 1944 Vs 6596 ± 1776m) and total collisions (28 ± 11 Vs 29 ± 13) were observed between both matches. There was a small albeit significant increase in IL-6, -8 and -10 concentrations pre to post-match in both PLB (IL-6: 0.83 ± 0.92 Vs 2.91 ± 1.40, IL-8: 2.16 ± 1.22 Vs 3.91 ± 1.61 and IL-10: 2.51 ± 2.14 Vs 0.61 ± 0.50 pg^.mL^-1) and MC groups (IL-6: 0.53 ± 0.53 Vs 2.24 ± 1.73, IL-8: 1.85 ± 0.96 Vs 3.46 ± 1.12 and IL-10: 0.48 ± 0.50 Vs 2.54 ± 2.10 pg^.mL^-1), although there were no significant differences between groups (P<0.05). Likewise, there was a small but significant increase in muscle soreness (P=0.01) and reduction in CMJ (P=0.003) with no significant differences between groups. No significant changes in sleep, fatigue or mood (P>0.05) were observed pre to post-match or between groups. These data suggest MC does not affect the modest changes observed in cytokine responses and markers of recovery from RL match-play.Keywords: Team Sport, Nutrition, Performance, Recovery.

Quantifying the Collision Dose in Rugby League: A Systematic Review, Meta-analysis, and Critical Analysis

BACKGROUND

Collisions (i.e. tackles, ball carries, and collisions) in the rugby league have the potential to increase injury risk, delay recovery, and influence individual and team performance. Understanding the collision demands of the rugby league may enable practitioners to optimise player health, recovery, and performance.

OBJECTIVE

The aim of this review was to (1) characterise the dose of collisions experienced within senior male rugby league match-play and training, (2) systematically and critically evaluate the methods used to describe the relative and absolute frequency and intensity of collisions, and (3) provide recommendations on collision monitoring.

METHODS

A systematic search of electronic databases (PubMed, SPORTDiscus, Scopus, and Web of Science) using keywords was undertaken. A meta-analysis provided a pooled mean of collision frequency or intensity metrics on comparable data sets from at least two studies.

RESULTS

Forty-three articles addressing the absolute (n) or relative collision frequency (n min^-1) or intensity of senior male rugby league collisions were included. Meta-analysis of video-based studies identified that forwards completed approximately twice the number of tackles per game than backs (n = 24.6 vs 12.8), whilst ball carry frequency remained similar between backs and forwards (n = 11.4 vs 11.2). Variable findings were observed at the subgroup level with a limited number of studies suggesting wide-running forwards, outside backs, and hit-up forwards complete similar ball carries whilst tackling frequency differed. For microtechnology, at the team level, players complete an average of 32.7 collisions per match. Limited data suggested hit-up and wide-running forwards complete the most collisions per match, when compared to adjustables and outside backs. Relative to playing time, forwards (n min^-1 = 0.44) complete a far greater frequency of collision than backs (n min^-1 = 0.16), with data suggesting hit-up forwards undertake more than adjustables, and outside backs. Studies investigating g force intensity zones utilised five unique intensity schemes with zones ranging from 2-3 g to 13-16 g. Given the disparity between device setups and zone classification systems between studies, further analyses were inappropriate. It is recommended that practitioners independently validate microtechnology against video to establish criterion validity.

CONCLUSIONS

Video- and microtechnology-based methods have been utilised to quantify collisions in the rugby league with differential collision profiles observed between forward and back positional groups, and their distinct subgroups. The ball carry demands of forwards and backs were similar, whilst tackle demands were greater for forwards than backs. Microtechnology has been used inconsistently to quantify collision frequency and intensity. Despite widespread popularity, a number of the microtechnology devices have yet to be appropriately validated. Limitations exist in using microtechnology to quantify collision intensity, including the lack of consistency and limited validation. Future directions include application of machine learning approaches to differentiate types of collisions in microtechnology datasets.

Cherry Gel Supplementation Does Not Attenuate Subjective Muscle Soreness or Alter Wellbeing Following a Match in a Team of Professional Rugby Union players: A Pilot Study

This study examined the effects of sour tart cherry juice (TC) on muscle soreness (MS) and wellbeing following a rugby union match in professional players. In a crossover design, 10 players from a senior squad in the top tier of England consumed either 2 × 30 mL servings of TC or an isocaloric cherry-flavoured control gel (CON) two days before, the day of, and two days following an 80 min match. Subjective wellbeing and MS were measured before the match (Pre), and for three days following the match (M+1, M+2, and M+3, respectively). MS was elevated from Pre at M+1 (CON, 111 ± 37 mm vs. TC 94 ± 41 mm) and M+2 (CON, 81 ± 35 mm vs. TC 72 ± 36 mm) (time effect; p = 0.0001; ηp² = 0.821) but there were no differences between TC and CON at either time point post-exercise (p = 0.807; ηp² = 0.035). Wellness scores were ~15% lower at M+1 (p = 0.023; ηp² = 0.638) but there were no differences between the two conditions at any time point (p = 0.647; ηp² = 0.160). In conclusion, tart cherry juice did not attenuate soreness or alter wellbeing in a team of professional rugby union players following a competitive match.

Incidence and characteristics of injury in under-19 academy level rugby league match play: A single season prospective cohort study

Academy rugby league competition is an important step along the pathway to professional status, but little is known about injury at this level of the game. The aim of this research was to establish the nature, incidence and burden of injury in English academy rugby league. Using an observational prospective cohort study design, and a time-loss injury definition, the injury outcomes of three professional rugby league academies were recorded during the 2017 season. A total of 87 injuries occurred in 59 matches for an overall injury incidence of 85 (95%CI 67-103) injuries per 1000 hours played. The mean severity of injury was 22 ± 19 days resulting in an overall injury burden of 1898 (95%CI 1813-1983) days lost per 1000 hours. The tackle event was the most common cause of injury (77% of all injuries). Forwards sustained a greater proportion of injuries than backs (forwards 67% vs. backs 33% of injuries). Concussion (13 (6-20) per 1000 hours) and ankle sprains (11 (4-17) per 1000 hours) were the most commonly diagnosed injuries. The shoulder joint was the most commonly injured site (17 (9-25) per 1000 hours). The incidence of injury for academy rugby league is similar to senior professional rugby league.

Are professional young rugby league players eating enough? Energy intake, expenditure and balance during a pre-season

Due to the unique energetic demands of professional young collision sport athletes, accurate assessment of energy balance is required. Consequently, this is the first study to simultaneously investigate the energy intake, expenditure and balance of professional young rugby league players across a pre-season period. The total energy expenditure of six professional young male rugby league players was measured via doubly labelled water over a fourteen-day assessment period. Resting metabolic rate was measured and physical activity level calculated. Dietary intake was reported via Snap-N-Send over a non-consecutive ten-day assessment period, alongside changes in fasted body mass and hydration status. Accordingly, energy balance was inferred. The mean (standard deviation) difference between total energy intake (16.73 (1.32) MJ^.day^-1) and total energy expenditure (18.36 (3.05) MJ^.day^-1) measured over the non-consecutive ten-day period was unclear (-1.63 (1.73) MJ^.day^-1; ES = 0.91 ± 1.28; p = 0.221). This corresponded in a most likely trivial decrease in body mass (-0.65 (0.78) kg; ES = 0.04 ± 0.03; p = 0.097). Resting metabolic rate and physical activity level across the fourteen-day pre-season period was 11.20 (2.16) MJ^.day^-1 and 1.7 (0.2), respectively. For the first time, this study utilises gold standard assessment techniques to elucidate the distinctly large energy expenditures of professional young rugby league players across a pre-season period, emphasising a requirement for equally large energy intakes to achieve targeted body mass and composition adaptations. Accordingly, it is imperative that practitioners regularly assess the energy balance of professional young collision-sport athletes to ensure their unique energetic requirements are achieved.

Impact-Induced Muscle Damage and Contact Sports: Etiology, Effects on Neuromuscular Function and Recovery, and the Modulating Effects of Adaptation and Recovery Strategies

Athletes involved in contact sports are habitually exposed to skeletal-muscle damage in their training and performance environments. This often leads to exercise-induced muscle damage (EIMD) resulting from repeated eccentric and/or high-intensity exercise and to impact-induced muscle damage (IIMD) resulting from collisions with opponents and the playing surface. While EIMD has been an area of extensive investigation, IIMD has received comparatively little research, with the magnitude and time frame of alterations following IIMD not presently well understood. It is currently thought that EIMD results from an overload of mechanical stress that causes ultrastructural damage to the cellular membrane constituents. Damage leads to compromised ability to produce force, which manifests immediately and persists for up to 14 d following exercise exposure. IIMD has been implicated in attenuated neuromuscular performance and recovery and in inflammatory processes, although the underlying course over time remains unclear. Exposure to EIMD leads to an adaptation to subsequent exposures, a phenomenon known as the repeated-bout effect. An analogous adaptation has been suggested to occur following IIMD; however, to date, this contention remains equivocal. While a considerable body of research has explored the efficacy of recovery strategies following EIMD, strategies promoting recovery from IIMD are limited to investigations using animal contusion models. Strategies such as cryotherapy and antioxidant supplementation that focus on attenuating the secondary inflammatory response may provide additional benefit in IIMD and are explored herein. Further research is required to first establish a model of generating IIMD and then explore broader areas around IIMD in athletic populations.

Collision activity during training increases total energy expenditure measured via doubly labelled water

PURPOSE

Collision sports are characterised by frequent high-intensity collisions that induce substantial muscle damage, potentially increasing the energetic cost of recovery. Therefore, this study investigated the energetic cost of collision-based activity for the first time across any sport.

METHODS

Using a randomised crossover design, six professional young male rugby league players completed two different 5-day pre-season training microcycles. Players completed either a collision (COLL; 20 competitive one-on-one collisions) or non-collision (nCOLL; matched for kinematic demands, excluding collisions) training session on the first day of each microcycle, exactly 7 days apart. All remaining training sessions were matched and did not involve any collision-based activity. Total energy expenditure was measured using doubly labelled water, the literature gold standard.

RESULTS

Collisions resulted in a very likely higher (4.96 ± 0.97 MJ; ES = 0.30 ± 0.07; p = 0.0021) total energy expenditure across the 5-day COLL training microcycle (95.07 ± 16.66 MJ) compared with the nCOLL training microcycle (90.34 ± 16.97 MJ). The COLL training session also resulted in a very likely higher (200 ± 102 AU; ES = 1.43 ± 0.74; p = 0.007) session rating of perceived exertion and a very likely greater (- 14.6 ± 3.3%; ES = - 1.60 ± 0.51; p = 0.002) decrease in wellbeing 24 h later.

CONCLUSIONS

A single collision training session considerably increased total energy expenditure. This may explain the large energy expenditures of collision-sport athletes, which appear to exceed kinematic training and match demands. These findings suggest fuelling professional collision-sport athletes appropriately for the "muscle damage caused" alongside the kinematic "work required".