Within this study, significant relationships were noted between selected GPS parameters and CMJ performance only. It was noted that as distance covered increased, percentage change in CMJ performance worsens (p < 0.05), implying that the distance covered by players during games had an effect upon resultant CMJ performance at 60 hours post-match. Time spent in D5 and D6 also presented a significant relationship with CMJ performance (p < 0.05) at 60 hours
post-match, meaning that practitioners could assume that a greater time spent in D6 would lead to a greater reduction in restoration of performance post-match play. From the results of this chapter, it was also interesting to note that decelerations (many of which are likely to be completed post D6 movements) were significantly correlated with CMJ performance at 90 hours post-match (p < 0.05). This view that a greater number of decelerations and time spent in the higher speed zones (D5 and D6) are correlated with reduced CMJ performance, would be of significant interest to practitioners when assessing outside backs’ restoration of
performance. When considering the large volume of the high intensity metrics (accelerations, decelerations and sprints) that backs complete within match play (as illustrated within Chapter 3), the role that this might have upon time-course of restoration of performance is further emphasised.
Prior research (Quarrie et al., 2013) recommends that practitioners provide forwards with more time to recover post-match than backs, given the greater contact loads they sustain, yet evidence from this study would dispute these views, when considering its results that show longer time-course of recovery associated with backs, compared to forwards. Despite strong correlations existing between forwards’ accelerations tasks and reduced CMJ performance (Table 7.3), no significant difference existed for CMJ performance at any time-point post-match. This point would therefore dispute the view that collision and contact situations were
responsible for reduced CMJ performance, as, in contrast to backs, no correlations were
observed between impacts and CMJ performance and no reduction in CMJ performance is noted amongst forwards at any time-point post-match. The larger number of Impacts > Zone 3 (noted within Chapter 3) attributed to forwards, perhaps suggests that forwards experience a large volume of blunt trauma during match play. Evidence from this chapter would, however, suggest that this trauma is not a factor in CMJ performance scores post-match. Instead, perhaps, the trauma that forwards experience is mainly upper body trauma associated with their positional tasks and therefore the resultant NMF that experienced affects the upper and not the lower body. Similarly, since CMJ measures lower body power via movement of the lower limbs, trauma to the lower body would be more likely to affect its performance than upper body. Upper body trauma is just as likely to occur during match play, yet the influence this has upon CMJ performance is questionable and should, therefore, be assessed via a more specific testing protocol.
7.5.4.1 Relevance of GPS parameters upon CMJ performance and WB scores between positional groups
On further analysis of the relationships between match variables across both positional groups, it was interesting to note that a significant relationship (p < 0.05) was noted between CMJ and accelerations at 60 hours post-match. It could, therefore, be argued that the existence within forwards, of this relationship between greater frequencies of accelerations at 60 hours post- match and reduced CMJ performance is perhaps due to forwards having to accelerate and decelerate into contact situations during games. These greater number of contact situations experienced by forwards, compared to backs, which was reported in previous research (Jones et al., 2015; Jones et al., 2014) (Forwards 31 ± 14; Backs 16 ± 7), could result in the significant relationship shown between forwards’ accelerations and CMJ performance in the days post- match. Despite backs completing more sprints and time spent in D6 during match play (as represented in Chapter 3), compared to forwards, the results from this chapter show that forwards perhaps experience a greater level of fatigue from acceleration tasks. Considering that many of forwards’ accelerations are performed prior to contact/collision situations and
therefore result in a greater level of neuromuscular fatigue, as represented by reduced CMJ performance, the relationship identified is perhaps more clearly understood. Additionally, when considering that forwards typically play for fewer minutes than backs (Table 3.4; Chapter 3), and therefore undertake a more intensified period of work, and that this study provides evidence of the effects of these on restoration, then this should be a major area of consideration for practitioners.
As a result of the aforementioned identification, that forwards experienced more impacts than backs (Chapter 3), this was perhaps an area that would have been expected to show positive correlations with CMJ performance and WB scores. However, when assessing the playing group as a whole (n = 59) no correlations existed amongst Im5 and Im6. Further analysis of both positional groups (forwards n = 31; backs n = 28) also showed no significant relationship between impacts and CMJ performance or WB scores. The absence of a correlation between impacts and delayed restoration of performance is somewhat surprising, yet could perhaps be explained by the small sample size within this research, and therefore one that warrants further investigation. This finding could also perhaps be explained by the notions proposed by both Lindsay, Lewis, Scarrott, Draper, and Gieseg (2015) and Reardon et al. (2016) that the force, angle and body parts involved in collisions are likely to be a determining factor influencing muscle damage and therefore restoration of performance. Considering the
significant relationship discovered regarding accelerations amongst forwards and reduced CMJ performance, along with the potential influence of accelerations into contact/collision
situations, the need to assess where the high level impact actually occur within positional groups’ match demands, is an area of potential future research. Improved ability of
practitioners to quantify where high level impacts occur within the match and whether or not they involved accelerations, decelerations and/or contact situations within the same instance of play, will shed further light upon player match demands and their probable effect upon restoration of performance.
7.5.5 Limitations of the research
Along with the aforementioned need to increase the sample size within this research, the main limitation involves the lack of multiple time-points post-match, upon which to assess change in CMJ performance and WB scores. Additional time-points, prior and post the 60 hours post- match, would have provided added value to the research. The inability of the researcher to gain additional testing time-points was due to logistical constraints of the players training schedule in the days post-match, meaning that access to players for assessment was limited. This limited access to players in the days post-match is considered a “real world” scenario within elite team sport settings, where days off from training are often employed to enhance recovery and improve performance restoration.
Another possible limitation with this study is that, similarly to previous research (Cormack, Newton, McGuigan, & Cormie, 2008; McLean et al., 2010), analysis of CMJ performance was focused upon outcome related variables. As discussed previously (Chapter 5), the analysis of kinetic variables that assess the SSC (specifically eccentric components of jumping movement) would provide more detail on the reasons for lack of restoration of performance. Despite the focus of this study being to detect time-course of recovery of CMJ and WB measures and not to detect NMF, it is perhaps also a limitation of the study, that no inclusion of kinetic values was made after considering the evidence presented by Gathercole, Sporer, and Stellingwerff (2015). Assessment of NMF and assessment of time-course of recovery are two distinct processes and should warrant separate testing protocols, although it should be noted that the link between
the two areas of focus could provide future direction for research practices. Lastly, despite biochemical analysis being an expensive and inconclusive performance measure (as outlined in chapter 2.4.4), its use in future investigation is warranted in order to gain a better
understanding of the physiological cost of games and perhaps help advise practitioners upon which activities to undertake in the days post-match. This lack of inclusion of physiological analysis of the performance decrement observed could therefore also be considered to be a limitation of this study.