Introduction:

Rugby union involves quick bouts of high-intensity action including tackling, jackalling, sprinting, and agility followed by low-intensity activity (Baker, 2002; Gabbett et al., 2008). Modern Rugby Union emphasises pace and pressure with and without the ball. Teams that support the ball carrier, clear rucks and produce quick ball are more likely to prevail over a disorganised defence and score. Conversely, a team that wins the defence race and pressures the ball carrier might force a mistake or pressurise a ruck by jackaling or stealing the ball, resulting in a turnover. Speed is crucial in Rugby Union, and Post-activation Potentiation Enhancement (PAPE) has been utilised to enhance speed within the training environment.

What is PAPE:

PAPE effect is defined as an improvement in neuromuscular performance following a previous workout known as the conditioning activity (CA) (Blazevich & Babault, 2019). In practice, the back squat comes before a biomechanically equivalent explosive activity vertical leap. However, performance is improved following CAs that include a modified movement pattern accomplished using similar muscles. For instance, bilateral power cleans or back squats are performed before sprints, which include repeated unilateral take-offs (Laurent B Seitz, Gabriel S Trajano, et al., 2014).

These regimens such as the above video can augment jumping, sprinting or track training. Numerous studies have demonstrated that performing some conditioning exercises at maximum or near-maximal intensities can improve sports performance immediately, assuming ample recovery time. PAP is the common moniker for the phenomenon being studied. Its application in sports has grown due to leaping advances (Suchomel et al., 2016; Tillin & Bishop, 2009) and sprinting (Seitz & Haff, 2016).

Which Exercises are Most Beneficial?

Numerous studies have studied various potentiation complex settings, focusing on exercise type, volume, and intensity as a CA. The largest PAPE impact was observed 5-7 minutes after low volume CA (1-3 sets) with high resistance (>85% 1RM) (Krzysztofik et al., 2021; Seitz & Haff, 2016; Wilson et al., 2013). Despite the similar movement pattern of CA and subsequent exercise (Gołaś et al., 2016), most studies used bilateral CAs to induce PAPE, despite most sports tasks being performed unilaterally (Krzysztofik et al., 2021; Seitz & Haff, 2016; Wilson et al., 2013).

Potentiation and exhaustion must be considered when using PAPE as an intervention. Rugby is a repeat sprint event, so a protocol must be altered to maximise sprint performance without overexerting an athlete (Bevan et al., 2010; Rassier & Macintosh, 2000).

While potentiation and fatigue are present simultaneously, fatigue declines faster. According to Tillin and Bishop (2009), Effective recovery can reduce fatigue and boost muscle performance. Insufficient rest can cause muscle tiredness and poor performance (Bevan et al., 2010). Professional Rugby players have better acceleration, speed, strength, and power than semi-professional and amateur players (Barr et al., 2014; Duthie et al., 2003; Mujika et al., 2009; Smart et al., 2013), thus finding optimal PAP strategies to enhance speed would be crucial.

Studies have shown that previous contractile activity, such as dynamic contractions or isometric maximum voluntary contractions (MVC), might improve athletic performance. The study by Till and Cooke (2009) incorporated vertical jumps as a means to assess enhanced performance measures, whilst Radcliffe and Radcliffe (1996) utilised horizontal jumps in their research to evaluate performance enhancements. Additionally, French et al. (2003) employed drop jumps as another measure of enhanced performance.

The current body of knowledge regarding the impact of PAP on sprint performance is relatively limited. In a study conducted by McBride et al. (2005), implementing a dynamic PAPE improved 40-meter sprint performance by 0.87%. Participants performed three sets of back squats at 90% of their 1RM to improve. Despite the many PAPE procedures, it is difficult to determine which are the most successful and at what intensities and approaches.

Enhancements in short-distance sprint trials like the above video were likewise documented subsequent to the completion of 10 sets of 1 repetition of back squats at 90% of one's maximum repetition (1RM), as reported by Chatzopoulos et al. (2007). Furthermore, Yetter and Moir (2008) observed similar improvements in short-distance sprint trials through the implementation of progressive sets of submaximal intensity back squats, ranging from 30% to 70% of one's 1RM. Previous studies have yielded varying outcomes regarding the impact of PAP on sprint performances. McBride et al. (2009) reported mixed results, while Till and Cooke (2009) found no significant effect of PAP on sprint performances.

What are PAP protocols that Involve Multijoint, Single Joint, Bilateral and Unilateral Techniques?

One of the primary reasons for selecting this topic is to determine whether there is a superior protocol for PAP and to distinguish between multi joint, single joint, bilateral, and unilateral protocols. This requires consideration of the muscle contraction generated by the PAP technique. The majority of research on sprinting has employed dynamic PAP protocols (Bevan et al., 2010; Chatzopoulos et al., 2007; Comyns et al., 2010; Linder et al., 2010; Till & Cooke, 2009; Yetter & Moir, 2008). Alternatively, Requena et al. (2011) and Till and Cooke (2009) have employed a single-joint isometric knee extension protocol. The findings were that isometric contractions elicit a higher recruitment of muscle fibres compared to dynamic contractions, perhaps leading to a higher degree of regulatory light chain phosphorylation and more pronounced alterations in muscle architecture (Requena et al., 2011; Till & Cooke, 2009).

It has been proposed that dynamic contractions tend to cause peripheral fatigue to set in quicker compared to isometric contractions (Babault et al., 2006; Kay et al., 2000; Newham et al., 1995; Ryschon et al., 1997; Tillin & Bishop, 2009), due to the build-up of lactate (Karelis et al., 2004). When players confront a high frequency of competitive engagements, it may be smart to consider using isometric workouts as a potential alternative for certain dynamic activities within an athlete's training regime. There is currently no consensus on whether an isometric or dynamic PAP method is beneficial for improving performance. The sparse number of research studies that specifically compare these two contraction kinds contributes to this lack of clarity. Furthermore, there is a significant discrepancy in the data on whether unilateral or bilateral isometric contractions are preferable. 

Rixon et al. (2007) discovered that performing three seconds of isometric maximal voluntary contraction (MVC) back squats resulted in a 2.9% increase in countermovement jump height. However, no improvement in countermovement jump height was detected after executing a 3-repetition maximum (3RM) dynamic back squat exercise. However, it is crucial to highlight that the two interventions are difficult to match in terms of volume/frequency, which makes comparing the PAP effects problematic. Hence, it is essential to ascertain if isometric contraction surpasses dynamic contraction in its efficacy to induce the PAP impact on future sprint performance.

The findings imply that integrating an isometric MVC protocol that involves several joints, as opposed to a single-joint MVC strategy, might potentially improve the efficacy of warm-up routines for maximising sprinting performance. Motor unit recruitment differs in single-joint and multi-joint activities, resulting in differences in activation patterns that may alter future PAP effects (Young & Elliott, 2001).

Isometric Training:

Isometric strength training (IST) has been documented as an effective method for enhancing isometric force production at the specific joint angle targeted during training (Kitai & Sale, 1989; Tillin et al., 2011). Additionally, it has been observed that IST does not have a significant impact on isometric force production at joint angles that were not included in the training intervention (Noorkõiv et al., 2014).

Research indicates that IST enhances angle-specific strength to a greater extent when compared to conventional dynamic strength training protocols (Kitai & Sale, 1989; Lee et al., 2018; Lum & Barbosa, 2019; Lum et al., 2022; Tillin et al., 2011). However, it must be noted that these studies are from longitudinal data. The back squat is the most researched PAP intervention which is shown in the video below for sprint performance, maybe because to the dynamic correlation of the triple extension phase movement (Verkhoshansky & Siff, 2009). Most studies have used 70% 1RM as the back squat intensity, Crewther et al. (2011) found no significant effect of back squat on sprint performance between 5 and 100m, while other studies had mixed interpretations (Bevan et al., 2010; Comyns et al., 2010; Lim & Kong, 2013; Wyland et al., 2015) and reported improved performance (Chatzopoulos et al., 2007; Linder et al., 2010; McBride et al., 2005; Seitz et al., 2014; Yetter & Moir, 2008).

Comyns et al. (2010) investigated the impact of repeated 3RM back squats 4 minutes before 30 m sprints. Sprint time, instantaneous, average, and maximal velocity were measured four times after the back-squat procedure. In the first session, the 30-meter time rose 1.4%, maximum velocity dropped 2%, and average velocity dropped 1.3% compared to baseline readings. The study found no statistically significant sprint measure gains across testing days. The authors found significant variations in instantaneous velocity at 20 and 30 metres between session 1 and 4. The results show that athletes may need frequent preload stimulus exposure to benefit. Similar findings were also observed by Yetter and Moir (2008). According to research, back squats at 90% of 1RM for three repetitions can immediately improve sprint performance from 5 to 40 metres. These improvements depend on athletes getting enough rest, usually 4–8 minutes (Healy & Comyns, 2017).

Physiological Mechanisms of PAPE:

Multiple mechanisms have been proposed to explain the phenomenon of PAP such as neural adaptations (Duchateau et al., 2021) and structural modifications (Morton et al., 2019). In summary, it has been observed that neural adaptations can manifest through; enhanced motor unit recruitment, synchronisation, firing rate, as well as reduced neuromuscular inhibition.  Additionally, changes in muscle architecture, such as fascicle elongation and/or fascicle angle widening (Coratella et al., 2022) along with the phosphorylation of myosin regulatory light chains (Tillin & Bishop, 2009). Furthermore, the reinforcement of the muscle-tendon complex has been identified as another aspect of structural adaptations (Tumkur Anil Kumar et al., 2021)

Coaches must be aware of the aspects that affect back squat PAP regimens. These include the athlete's strength and squat depth. Squat volume and rest length will vary across athletes. Multiple investigations have shown that PAP response is highly personalised (Lim & Kong, 2013; Till & Cooke, 2009). Thus, standard group statistics may not reliably detect PAP's favourable benefits (Comyns et al., 2010; Harrison, 2011; Whelan et al., 2014).

Thanks for reading.... Chris

 

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