PENDIENTES DE CUBIERTAS PLANAS

Training status is consistently observed to delineate results, with those of higher training status showing greater propensity for performance improvement post-CC (Berning, et al., 2010; Chiu, et al., 2003; Rixon, et al., 2007). Movement execution is already highly coordinated and level of recruitment already maximised in high-level athletes and, as such, these participants would be more able to capitalise on the increased functional capacity PAP affords (D. J. Smith, 2003). Association of skill level to training status further suggests that the small degree of improvement afforded by PAP would be clouded by the inherent performance variability of unskilled participants (Langdown et al., 2012; Sakurai & Ohtsuki, 2000). In addition, a higher training status implies a greater fatigue resistance. However, studies testing participants of lower training status have still shown positive response, and the CC protocol and recovery time allowed post-CC may simply need to be participant-appropriate (Chiu, et al., 2003). Confirming characteristics determined by TP, Chui et al. (2004) and Terzis et al. (2009) both established a correlation between PAP response and expression of myosin heavy chain (MHC) type II isoforms - those of higher type II content demonstrating greater response. Accordingly, magnitude of PAP appears to be higher in sprint trained athletes (Bomfim Lima, et al., 2011). However, endurance athletes, characterised by a more prevalent expression of

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type I MHC isoforms, have still shown some degree of effect (Boullosa, et al., 2011; Hamada, Sale, & Macdougall, 2000). Comparing the 2 types of athlete, Paasuke et al. (2007) suggest that an increased fatigue resistance in endurance-trained athletes would allow PAP response to more readily prevail. While the magnitude of response may be lower, the study observes a potentiated performance improvement that is sustained over a longer time frame in endurance athletes.

Studies that median-split trial groups based on measures of strength found increased results in stronger participants (Gourgoulis, et al., 2003). Others observed a positive correlation between strength and the magnitude of response (Bellar, et al., 2012; Kilduff, et al., 2008; Ruben, et al., 2010) and a negative correlation with recovery time required to observe positive effect (Jo, et al., 2010). Studies in female participants show equivalent outcomes to that of males (DeRenne, 2010), but, where sex comparison is made within a trial, results are divided – studies equally report no difference (McCann & Flanagan, 2010) or else a greater response in males (Radcliffe & Radcliffe, 1996; Rixon, et al., 2007; Terzis, et al., 2009). Those studies reporting distinction may simply have acknowledged strength-mediated difference rather than sex per se.

A large number of studies agree that overall response is highly individualised (Comyns, et al., 2006; Crewther, et al., 2011; McCann & Flanagan, 2010; Nibali, et al., 2011; Till & Cooke, 2009; Turki, et al., 2011). This has been most commonly infered from the distinct recovery times needed to observe an increased, as opposed to decreased or unchanged, performance measure (Bevan et al., 2009; Chaouachi, et al., 2011; Jo, et al., 2010). The expression of potentiation and fatigue in succeeding performance is, evidently, dictated by the CC variables, but mediated by the characteristics of the participant themselves. The outcome response is then characterised by a unique time window shaped by both. This conclusion alone highlights the inherent difficulty in establishing significant group effects in PAP studies.

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2.5.3.3 Performance Outcomes

Studies observing PAP in ballistic action of the lower and upper limb (Baker, 2003; Boullosa, et al., 2012), repetitive or cyclical explosive action (Okuno, et al., 2013; Thatcher, et al., 2012), concentric or stretch-shortening influenced exercise modes (Fletcher, 2012) and speed-power performance of varying durations (Feros, et al., 2012; Matthews, et al., 2004), suggest CC protocols can influence performance gain in many performance modes so long as conditions for observing PAP are optimised and biomechanical specificity is achieved.

Closer inspection suggests that the CC protocol might have distinct effects on discrete phases of performance, consequent to the kinematic and kinetic profile therein (Yetter & Moir, 2008). In studies where the key performance measure, such as distance or time, is unchanged, an improved biomechanical profile has often been observed in the post-CC test (Esformes, et al., 2011; Kilduff, et al., 2011). Further, Chiu and Salem (2012) have shown variance in the PAP response at each joint contributing to the performance movement. It is possible, then, that movement strategy and/or performance conditions could subsequently be altered to take advantage of functional improvements afforded by PAP. While results of the Comyns et al. (2010) study suggest that a learning effect may exist, contrasting opinions are upheld on the degree to which PAP response can be trained (Sale, 2002; G. G. Sleivert et al., 1999). Few longitudinal studies exist and more research is required to substantiate this proposition.

In conclusion, evidence suggests that prior exercise influences both fatigue and potentiation of subsequent performance. While the effects co-exist, execution of a maximal or near-maximal CC prior to acute exercise performance may affect a net performance gain through increased excitation of the neuromuscular pathways and improvements in electro-mechanical efficiency. Mechanisms of

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potentiation appear to exist along the chain of command with increased central processing, highest order MU recruitment and sensitivity of the cross-bridge mechanism, together with architectural improvements in force transmission, reduction in EMD and a more beneficial metabolic environment, offering the possibility of increased force production or rate of force development. Studies of PAP in ballistic exercise present a number of factors that must be reconciled for prevailing conditions of potentiation to be achieved. The complex interaction of type-intensity-volume-density of CC protocol creates a distinct time window of effect that is further mediated by the individual’s training and fibre-type characteristics. Influence of PAP across discrete phases of the goal movement further reflects a biomechanical specificity of response congruent to performance across the force- velocity relationship. The performance coach or sports scientist must, therefore, understand and consolidate these observations in order to create a successful outcome.

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