PROPUESTA DE INTERVENCIÓN

RECOMMENDATIONS FOR FUTURE RESEARCH

The general limitations within this thesis are presented below. These limitations are accompanied by recommendations for future research in this area.

• Despite the previously established fatiguing nature of the exercise protocol used in Chapter 4 (Serpiello, McKenna et al. 2011), the recreationally active participants in this thesis were able to maintain their repeat sprint performance, regardless of the use of a recovery intervention. Thus, it was not possible to investigate the influence of compression garments on the maintenance of performance across multiple days. Previous use of this protocol in a similar participant population demonstrated that mean power decreased by 4.8% in set 3 versus set 1 (ES = -0.21 ± 0.07), peak power was reduced by 9.2% (ES = -0.28 ± 0.11), and mean velocity declined by 2.2% (ES = -0.18 ± 0.33) (Serpiello, McKenna et al. 2011). Even after ten sessions of repeated sprint training decrements in performance were observed. For example, mean power in set 3 was 4.1% lower than set 1 (ES = -0.19 ± 0.06), and mean velocity was reduced by 2.1% (ES = -0.17 ± 0.06). Future investigations should adopt a more demanding protocol to ensure that there is a substantial reduction in performance. It may be that the inclusion of additional sets of sprints, and/or longer sprint duration will achieve this. Ultimately, intensive pilot testing across multiple days is required to ensure the fatigue inducing nature of the protocol and its application to team sport scenarios.

• Sub-elite team sport athletes, or recreational team sport participants should have been identified as the cohort to be recruited for this study to enhance the transference of results to elite team sport athletes. This was a limitation of this study when

determining the practical applications of the findings. Future research should ensure the appropriateness of the cohort selected to improve the validity of the results. • The repeat sprint protocol in Chapter 4 failed to produce immediate muscle damage

as indicated through plasma [Mb]. Plasma [Mb] was only substantially elevated 24 hr after three RSE sessions in Spo only. This made it difficult to draw meaningful conclusions regarding the usefulness of compression garments to influence post exercise plasma [Mb]. It was expected that the deceleration phase of the 15 sprints in each RSE would elicit substantial muscle damage (Williams 1985). Alternatively, a protocol such as the Loughborough Intermittent Shuttle Test may be more appropriate. This test is designed to replicate soccer specific running activity (Nicholas, Nuttall et al. 2000) and elicits muscle damage even 48 hr after its completion in recreational exercisers (Thompson, Nicholas et al. 1999). The reproducibility of this running test has also been established, with no differences in performance and physiological parameters when participants unfamiliar with the protocol were tested 7 days apart (Nicholas, Nuttall et al. 2000). In addition, the activity pattern and the physiological and metabolic responses closely simulate the game demands of soccer (Nicholas, Nuttall et al. 2000), an intermittent running based team sport. The disadvantage of the Loughborough Intermittent Shuttle Test is its longer duration of approximately ~90 min, placing a far greater time requirement on participants.

• Although the magnitude of treatment effects for perceptual measures were greater than the SWC for muscle soreness and fatigue, a noticeable level of individual variation in perceptual responses in this thesis was apparent. It is likely that individual differences in the interpretation of the word anchors at either end of the VAS, for example ‘no fatigue’ and ‘very severe fatigue’ varied between participants 177

(Wewers and Lowe 1990). Although shown to be a sensitive measure to assess changes in pain scores (Seymour 1982; Du Toit, Pritchard et al. 2002), this limitation was likely compounded by the ability to accurately mark the VAS in the same position. To minimise this variation, participants should be thoroughly familiarised with the VAS. The familiarisation should include a detailed description of muscle soreness and general fatigue at both ends of the VAS to allow participants to more accurately interpret and mark the VAS. Moreover, it may be beneficial to collect multiple baseline scores to ensure a more accurate reflection of a relatively fatigue and soreness free state. The latter may be troublesome within an elite athlete environment, where athletes often experience fatigue and soreness to some extent due to the hectic training and competition cycle.

• Data in Chapter 5 was collected during a critical phase of the AF pre-season, with the actual testing days forming an important component of this phase. With this in mind, combined with limited access to participants, it was not possible to conduct a cross-over study.

Limited player access also prevented the quantification of neuromuscular fatigue through a CMJ, perceived muscle soreness and fatigue, and plasma [Mb] levels immediately after training. This may have hindered the ability to detect recovery effects, as it remains unknown if all participants experienced the same recovery requirement. What’s more, only collecting a recovery sample at +24 may have missed recovery effects associated with compression garments that occurred at an earlier time point.

It was also not feasible to control the amount of work conducted during each session. Future research should quantify the amount of work conducted during each

component of the training session. For example, it would have been desirable to conduct GPS analysis on the small sided game, running and skills component of training to identify possible between group differences; however access to the GPS units was not available at the time.

The use of sub elite participants in future studies may help overcome some of the issues associated with access to participants, control of training activities and the inclusion of a cross over design.

• The time point at which recovery was assessed following AF competition (Chapter 6) may have been inappropriate to detect recovery effects. Multiple variables (perceptual and biochemical) had returned to pre competition levels, making treatment effects difficult to detect. However, the time at which data was collected represented the actual time that the club conducted their first session after the game and is reflective of the clubs regular schedule. Future research should consider multiple sampling points throughout the recovery period to establish a time course of recovery for each parameter. Particularly, data should be acquired 24 hr after competition, as substantial perturbations in performance, perceptual and biochemical parameters were present following AF training at this time point. With the longer duration of games it is anticipated that at +24 after a game that considerable treatment effects may be detected.

• Although desirable, it was not viable to acquire data from multiple games in Chapter 6. This was attributed to data collection occurring during the competition season. Initially, two games were selected for investigation, which were reduced to a single game due to club imposed restrictions. This also precluded the use of a cross over design. As mentioned above, the use of sub elite participants may help overcome the issue of access to participants, which may allow for a cross over design across

multiple games. Combined with sampling at +24 rather than +40 (see above point), this larger sample size should allow for a greater opportunity to detect recovery effects. When selecting multiple games, consideration of the oppositions skill level must be considered to ensure all games are played against opponents of equal standing to prevent any bias in the data.

• An intrinsic limitation of compression garment research is the inability to blind participants, and to include a placebo. The use of elite participants (Chapter 5 and Chapter 6 compounded this, due to regular use of compression garments, and the accompanying familiarity with the sensation of wearing such garments. As such, it was not really a viable option to include elasticised (with very low levels of compression) pants as a placebo group. Similarly, many of the recreationally active participants involved in the repeat sprint study (Chapter 4) were accustomed to wearing compression garments. To overcome this limitation, it may be useful to record the participants’ level of belief in the intervention, possibly through a VAS, prior to the study, which may later be used as a covariate during the analysis phase. This may be broken down into specific parameters such as muscle soreness, fatigue, performance, general recovery etc as the level of belief may vary across different parameters. It may also be useful when completing the investigation into the individuals level of belief to map brain activity. The use of functional MRI while completing ‘belief’ VAS/questionnaires would allow the measurement of the activity in the medial orbitofrontal cortex (Plassmann, O'Doherty et al. 2008), a region know to encode for experienced pleasantness (McClure, Li et al. 2004; Rolls, Grabenhorst et al. 2008). This information would help neurologically quantify the participants’ expectations regarding the positive recovery effects of the compression garments.

• Compression garments are anticipated to exert positive actions on post exercise recovery namely through alterations to the vascular and lymphatic systems (Swedborg 1984; Mayberry, Moneta et al. 1991; Yasuhara, Shigematsu et al. 1996; Johansson, Lie et al. 1998; Jonker, de Boer et al. 2001; Beidler, Douillet et al. 2009). Although perceptual and performance recovery was enhanced at times with compression use in this thesis, the physiological mechanisms alluding to this improved recovery were not investigated. The focus of this thesis did not extend to such investigation, particularly in Chapters 5 and 6, as testing was conducted with elite participants in training and competition scenarios were access to participants was highly restricted. There are multiple non-invasive methods to measure limb blood flow including Doppler ultrasound (Chleboun, Howell et al. 1995; Hsieh and Lee 2005), tissue oxygenation measured using near infrared Spectroscopy (Bringard, Denis et al. 2006; Dascombe, Hoare et al. 2011; Coza, Dunn et al. 2012) and venous occlusion plethysmography (Bochmann, Seibel et al. 2005) that could be incorporated into future investigations.

Compression garment mediated reductions in swelling and odema, through a mechanical blocking of odema, and improvements in vessel wall hydrostatic pressure, are suggested to minimise perceptions of muscle soreness (Kraemer, Volek et al. 2000; Jonker, de Boer et al. 2001). A non-invasive method to indirectly quantify swelling is the measurement of limb circumferences, which has been used in previous studies (Chleboun, Howell et al. 1995; Eston and Peters 1999). It is important that such investigations take into consideration exercise mediated changes in blood flow and limb circumference that may not be directly related to muscle damage or the use of compression garments.

It has been hypothesised that muscle soreness, secondary to damage inducing exercise, may reduce neural drive to the muscles, contributing to perceived fatigue (Racinais, Bringard et al. 2008). Indeed Duffield et al reported depressed evoked twitch properties 2 hr after damaging exercise which were associated with elevated markers of muscle damage 24hr later (Duffield, Cannon et al. 2010).