Periodisation of Eccentrically-Integrated Resistance Training during a National Rugby League Pre-Season

Successful performances in rugby league require the ability to engage in repeated contact efforts with minimal recovery while maintaining a high running intensity. The capacity to express high levels of time-limited force appears to underlie many important physical attributes required to meet the repeated-effort demands of rugby league play. If appropriately periodised and integrated into the training plan, resistance exercise that sufficiently loads the eccentric phase of movement may provide a beneficial stimulus to improve players’ force-generating capacity. Comprehensive reviews relating to the adaptive effects of eccentric training and the methods most commonly prescribed in practical environments are available and may provide context for applying these strategies. However, no literature to date has specifically discussed the planning and programming of eccentric resistance exercise to enhance force production characteristics in elite athletes. Therefore, this narrative review focuses on the periodisation of eccentrically-integrated resistance training during a 17-week National Rugby League pre-season phase. To help guide programming during the pre-season period, the 17-week timeline is divided into several phases (i.e., general preparation, special preparation, active rest, and pre-competition). Within the periodised model, eccentric exercise parameters (i.e., volume, load [% 1RM]) are manipulated to progressively increase the rate of muscle lengthening velocity over the pre-season phase and sequentially elicit changes in muscle-tendon properties and neural function that culminate in improving muscular strength expression.


INTRODUCTION
Well-developed physical capacities (e.g., muscular strength and power, maximal running speed, change of direction, aerobic power) are required to meet the high-intensity activity demands of rugby league competition (Johnston, Gabbett, & Jenkins, 2014). Players generally travel ~85-100 m per minute and total distances of ~5,000-8,500 m, with 250-750 m of this at high-speed (≥ 5.5 m.s−1) and completing 1.1 ± 0. 56  A systematic approach to training is generally applied in most sporting environments to elicit the physiological adaptations underlying the expression of muscular strength (Baker, Wilson, & Carlyon, 1994;Suchomel, Nimphius, Bellon, & Stone, 2018). If appropriately periodised and integrated into the resistance training plan, eccentric exercise may be particularly beneficial in enhancing maximal and time-limited force expression (Suchomel et al., 2019a). Comprehensive reviews relating to the adaptive effects of eccentric training (Douglas et al., 2019a,b;Handford et al., 2022) and the methods most commonly prescribed in practical environments (Suchomel et al., 2019a,b) are available and may provide context for applying these strategies. However, no literature to date has specifically discussed the planning and programming of eccentric training methods to enhance force production characteristics in elite athletes. Therefore, this narrative review focuses on the periodisation of eccentrically-integrated resistance training during a National Rugby League (NRL) pre-season phase.
primary macrocycles (i.e., pre-season, competition, and off-season phases) (Kelly & Coutts, 2007). Preseason rugby league training typically spans 17 weeks (November-February) and generally involves frequent bouts of resistance exercise that aim to develop the muscular strength required to meet the physical demands of competitive match-play (Baker et al., 1994;de Lacey et al., 2014;McLean, Coutts, Kelly, McGuigan, & Cormack, 2010). To help guide programming during the pre-season period, the 17week timeline is divided into several phases (i.e., general preparation, special preparation, active rest, and pre-competition). Within the periodised model, eccentric exercise parameters (i.e., volume, load [%1RM]) ( Table 1) are manipulated to progressively increase the rate of muscle lengthening velocity over the pre-season phase and sequentially elicit changes in muscle-tendon properties and neural function that culminate in improving muscular strength expression (Figure 1). The following sections discuss the implementation of eccentric resistance training within an NRL pre-season based on the available evidence.

GENERAL PREPARATION PHASE
The primary aim of the 4-week general preparation phase (GPP) is to increase muscle hypertrophy and raise work capacity (i.e., force production capacity [O'Bryant, Byrd, & Stone, 1988]) in order to improve the potential for players to repeatedly express large amounts of time-limited force (Stone, Sands, & Stone, 2007). Exercise parameters (e.g., 70-75% 1RM) are manipulated to slow (5 sec [Krzysztofik, Wilk, Wojdala, & Golas, 2019]) the eccentric phase of movement and therefore augment time under tension (i.e., the time a muscle is held under tension or strain during an exercise set [Handford et al., 2022]) and elicit high resistance training volumes.
Metabolic stress within a muscle through a resistance exercise stimulus of sufficient magnitude results in the upregulation of muscle protein synthesis and, subsequently, protein accretion and changes in muscle size (Schoenfeld et al., 2021). Increases in muscle protein synthesis rates within the day following lower-body resistance exercise involving submaximal intensities performed with a 6-sec lowering phase until volitional fatigue have been reported (Burd et al., 2012). This suggests that maximal fibre activation may not exclusively drive muscle protein synthesis rates (Burd et al., 2012). Increasing exercise volume, through increasing time under tension during the eccentric phase of movement, may also stimulate protein accretion and lead to muscle growth despite lower resistance exercise loads (Burd et al., 2010;Schoenfeld, 2010;Terzis et al., 2010). Greater time under tension during muscle lengthening actions with moderate loads can result in larger accumulations of blood lactate, growth hormone, and testosterone when compared to volume-matched eccentric exercise involving faster tempos (Kraemer & Castracane, 2015). With repeated exercise bouts, these acute hormonal responses can produce increases in muscle size (Godfrey, Whyte, Buckley, & Quinlivan, 2009;Kraemer & Castracane, 2015). This may explain the increases in muscle hypertrophy following 12 weeks of resistance exercise involving a 4-sec eccentric phase of movement with moderate loads (~81% CON 1RM) in resistance-trained males (Pereira et al., 2016). The improvements in muscle size were attributed to the prolonged eccentric phase of movement and therefore a heightened time under tension (Schoenfeld, 2010) that may have elicited substantial metabolic stress (Lieber & Friden, 1988;Stauber, 1988) and subsequent increases in muscle size following the training intervention (Schoenfeld et al., 2021).
Evidence suggests that sarcoplasmic hypertrophy (i.e., an increase in sarcoplasmic volume and its constituents [e.g., fluid, enzymes, organelles] [Roberts, Haun, Vann, Osburn, & Young, 2020]) contributes to increases in muscle size following higher volume resistance training (Haun et al., 2019a) and that these changes support subsequent myofibril hypertrophy (Roberts et al., 2020). Data show that increasing the time under tension during the eccentric phase of movement (~6 sec) increases the amplitude of sarcoplasmic protein synthesis within 6 h of the exercise bout and results in a delayed simulation of myofibril accretion 24-30 h post-training (Burd et al., 2012). Myofibrillar protein synthetic rate was also shown to be associated with p70S6K phosphorylation within this time frame following the training session (Burd et al., 2012). Previous findings have demonstrated that the increase in p70S6K 6 h following resistance exercise involving highresistance muscle lengthening actions is almost perfectly correlated to the percent change in muscle mass after 6 weeks of training (Baar & Esser, 1999). As such, transient increases in sarcoplasmic protein synthesis rates following slow eccentric resistance exercise with relatively higher exercise volumes and submaximal loads may support subsequent increases in myofibril hypertrophy (Haun et

ACTIVE REST
The 2-week active rest period occurs over the holiday season and aims to promote recovery following previously strenuous training through substantially lower resistance training volume-loads compared to the other pre-season phases (Bompa & Haff, 2009). Eccentric training is not programmed during this period so that neuromuscular fatigue is minimised. A supercompensatory effect whereby improvements in psychophysiological state and performance occur has been reported following active rest periods (

SPECIAL PREPARATION PHASE
The primary aim of the 4-week special preparation phase (SPP) is to elicit the physiological adaptations underlying improvements in neuromuscular function. Compared to previous training phases, the SPP involves reduced exercise volumes, high-loads (≥ 90% 1RM), and fast (< 2 sec ) muscle lengthening actions.
High force outputs may be achieved with fast lengthening actions given that muscle force production is not constrained by lengthening velocity during the eccentric phase of movement (Edman, 1988). As such, muscle size and strength gains, which are generally proportional to the degree of overload (Martino, Perestrelo, Vinarsky, Pagliari, & Forte, 2018), may be elicited through heavy resistance exercise involving fast eccentric actions (Douglas et al., 2017a). Greater muscle growth has been reported following maximal eccentric exercise involving a fast compared to a slow lengthening speed (English et al., 2014;Farthing & Chilibeck, 2003;Shepstone et al., 2005). This may be due to the larger magnitude of muscle damage and subsequent anabolic response produced with fast eccentric training when compared to load-matched slow eccentric training ( (2005). Furthermore, the shift toward a more fatigueresistant phenotype generally occurs with greater volume-loads (Andersen & Aagaard, 2000). As such, the differences in average weekly (3.14 rad.s-1 suggest that there may be a pattern of decreased force production due to fibre remodelling that subsequently improves the type II:I fibre ratio and increases muscle hypertrophy following fast, heavy eccentric training (Shepstone et al., 2005). This may provide an explanation of the delayed training effects often observed following similar training protocols did not investigate changes in muscular properties (i.e., fibre composition), which are associated with earlyphase RFD (Bottinelli, Pellegrino, Canepari, Rossi, & Reggiani, 1999). Additionally, the study participants were recreationally-trained. As such, the substantial improvements in force-generating capacity may be due to their training status (Aagaard, 2003;Seynnes et al., 2007). Although a similar increase may not occur in professional rugby league players, neural plasticity is evident in individuals with highly augmented neural function (Aagaard, 2003). These results suggest that increasing the speed of highload lengthening actions may elicit improvements in neural function that subsequently increase RFD at the early phase of rising torque.
Findings suggest that improvements in force-time characteristics are more evident when the testing velocity matches that generally used in training (Roig et al., 2009). Studies have shown that highload eccentric training with slow lengthening actions can improve sprint and jump performance (Cook, Beaven, & Kilduff, 2013;Stasinaki et al., 2019). Increases in upper-and lower-body maximal strength and countermovement jump performance were found following 3 weeks of heavy (120% CON 1RM) eccentric training in semi-professional rugby players (Cook et al., 2013). However, 40 m sprint performance was only improved when fast, unloaded eccentric exercises (i.e., assisted countermovement jumps and downhill running) were added to the protocol (Cook et al., 2013). Training that progressively exposes players to faster lengthening actions may improve motor control and time-limited force expression to a greater degree compared to training involving slower lengthening actions (Handford et al., 2022;Suchomel et al., 2018). This may elicit a large transfer of training effect (particularly after training-induced changes in muscle-tendon and neural function have occurred [Cormie et al., 2010]) that subsequently enhances many physical attributes associated with a broad range of technical and tactical skills (

PRE-COMPETITION PHASE
The realisation of delayed training effects following eccentric training may require considerable time (Baroni et al., 2013;Coratella & Schena, 2016;Leong et al., 2014;Shepstone et al., 2005). As such, high-load eccentric training with fast lengthening actions is prescribed with lower volumes during the 4-week pre-competition phase to allow for adequate recovery while maintaining high levels of force production. Plyometric training involving high rates of muscle lengthening is performed subsequent to fast, heavy eccentric exercise during training sessions to further elicit the morphological and neural adaptations underlying improvements in timelimited force expression and enhance motor control (Golas,

CONSIDERATIONS AND LIMITATIONS
Although eccentric training appears to be a beneficial strategy to improve rugby league performance, several factors need to be considered.  Stone, 2015) in response to eccentric training. A fourth consideration is the assignment of eccentric exercise loads. As force output is task-specific, prescribing eccentric loads based on tasks limited by concentric strength may not take advantage of the high levels of mechanical tension that can be elicited by eccentric exercise (Harden et al., 2019). Nevertheless, specialised equipment that may not be available in most practical environments is likely needed to establish maximal eccentric strength levels . Fifth, the training age and technical proficiency of players should be considered when prescribing eccentric training to reduce the chance of maladaptive outcomes (Suchomel et al., 2019b). Sixth, the decision to  Notes: *Session includes upper-and lower-body eccentric exercise (i.e., back squat, bench press); **resistance exercise parameters are selected based on a player's identified physical deficiencies and positional requirements GPP general physical preparation; PCP pre-competition phase; SPP special physical preparation prescribe eccentric training should be informed by the physical demands of competition together with an individualised approach that addresses movement deficiencies and consideration of other sport-related training. Importantly, the pre-season programme illustrated is a general representation and does not reflect possible modifications due to changes in player health and performance and positional requirements that will ultimately guide resistance training prescription. Lastly, eccentric resistance training should be appropriately periodised to elicit a systematic and progressive overload over the preseason phase (Figure 2). If appropriately periodised and integrated into the training plan, resistance training that sufficiently loads the eccentric phase of movement and progressively increases the rate of muscle lengthening velocity over the pre-season phase can provide a beneficial stimulus to elicit morphological and neural changes that culminate in improving muscular strength expression.