Influencing Performance on Match-Day: A Specific Look at Subs, Goalkeepers and Half-Time Interventions

INFLUENCING PERFORMANCE ON MATCH-DAY:

A SPECIFIC LOOK AT SUBS, GOALKEEPERS AND HALF-TIME INTERVENTIONS

FEATURE / DR MAYUR K RANCHORDAS

While the implementation of training and preparatory practices occupies the majority of a practitioner’s workload, football matchday also provides opportunities to positively influence performance. Recently, a number of intervention opportunities relating to the practices of substitutes, goalkeepers and consideration of half-time strategies have been identified in the literature. Whilst practical and logistical constraints may often represent substantial hurdles to overcome, by considering match-day demands and responses on an individual player level, it is possible to tailor training, nutrition, and/or recovery treatments accordingly. The following article presents a commentary on how recent research focused on bespoke populations and scenarios may provide practitioners with opportunities to modify match-day protocols for enhanced performance in football players.

Substitutes

Although exceptions exist (e.g., in the case of injury, or where providing playing time to certain individuals represents a key objective), substitutes are usually introduced at half-time or during the second-half of a match; a fact which presents several areas for consideration when seeking to optimise the treatment of this playing group[2-4]. For substitutions made with the aim of providing fresh energy to a team, it is vital that players entering the pitch are appropriately prepared to produce high and sustained physical outputs, with minimal risk of injury. The length of time elapsing between the end of the pre-match warm-up and eventual match-introduction has the potential to negatively affect a substitute’s ‘preparedness’[1-3] via mechanisms potentially linked to progressive decreases in body temperature. For this reason, ensuring that substitutes engage in adequate warm-up and rewarm-up activity (potentially in conjunction with the use of passive heat maintenance techniques) prior to pitch-entry may be of utmost importance – especially in typical weather conditions in the UK. However, despite acknowledging that a substitute entering the pitch following inadequate preparations may negatively impact upon overall team performance[4] , published and empirical observations suggest that many teams allow awaiting substitutes to autonomously determine the preparatory strategies adopted between kick-off and pitch-entry[2, 4] , often resulting in minimal rewarm-up activity being performed[2, 4] .

Many stadia provide limited space where substitutes can perform rewarm-up activities, and professional competitions often require club staff to remain within the technical area whilst a match is underway. Despite these substantial barriers, savvy practitioners may recognise the potential to directly influence the activities performed by substitutes during the pre-match and half-time periods (when it may also be possible to use certain areas of the pitch and/or to perform tasks involving the use of a ball or other equipment). Moreover, establishing a culture of buy-in may allow for effective player-education and/or the provision of specific recommendations surrounding the importance of pre-pitch-entry preparation. In the absence of regulatory changes to allow staff to directly lead all pre-pitchentry rewarm-ups, these strategies may represent a means by which practitioners can positively influence a substitute’s ability to deliver the desired match-impact, alongside potentially reducing injury-risk.

Another striking consideration is the substantial discrepancy in match-play demands often faced by substitutes compared with whole-match players. Indeed, irrespective of the relative (i.e., per min of playing time) physical responses observed, a substitute’s shorter match-exposure is likely to elicit lower absolute physical demands compared with if a full 90 min had been played. As preparation and recovery strategies should be determined based upon the specific demands faced by any athlete, such observations suggest a benefit to bespoke treatment of substitutes. Whilst uncertainty surrounding a substitute’s likely match-play demands (e.g., the potential requirement to play substantially longer than anticipated due to injury to a starting player) may preclude the adoption of tailored pre-match strategies (e.g., fuelling, tapering, priming, etc.), it seems logical that post-match training and recovery practices could be individualised. It is widely recognised that ‘top-up’ conditioning sessions may be beneficial to offset reductions in high-intensity loading for substitutes compared with wholematch players[4]. However, substantial variation exists with regards to the objectives and modalities adopted within such sessions, and barriers such as pitchprotection policies, travel, and scheduling considerations may often impose limit their duration and/or content. In addition, whilst some practitioners may tailor carbohydrate consumption and/or withhold cold water immersion strategies, adopting bespoke recovery strategies for substitutes appears to be relatively uncommon[4]. As match-play demands may vary markedly even amongst substitutes (e.g., depending upon playing time), preparation and recovery provision may require further individualisation.

Goalkeepers

As goalkeepers typically remain near the goal-line that they tasked with protecting, it is unsurprising that goalkeepers cover ~50% of the match distances of players in outfield positions[5]. Acknowledging that other metabolically challenging tasks such as long kicks, jumps, and dives may also be performed, these lower physical demands may necessitate unique fuelling and recovery practices. Indeed, like substitutes, goalkeepers may not require the same aggressive recovery strategies like those recommended for outfield players who play a whole match[6], even during periods of fixture congestion. White et al.[5] also documented the training demands of professional goalkeepers throughout an in-season microcycle. For practitioners seeking to appropriately manage training loads and/or prescribe nutritional strategies, it is notable that training activities that typically elicit the highest physical loads amongst outfield players did not reflect the most demanding activities for goalkeepers. Indeed, for certain goalkeeper-specific metrics such as dives

and jumps, match-days elicited amongst the lowest loading of any day within a week. Such observations highlight how practitioners may need to consider training and nutritional periodisation individually for goalkeepers, rather than on a whole-squad basis.

Half-time Nutritional Considerations

The half-time period has become increasingly recognised as an opportunity to improve second-half performance via strategies such as tactical debriefing and the use of active and/or passive heat maintenance techniques. Moreover, as maintenance of blood glucose concentrations may offer benefits in terms of physical performance, decisionmaking, and/or the ability to execute soccer-specific technical skills[7], it is common practice for football players to consume carbohydrate-electrolyte beverages prior to kick-off and during half-time. Notably, most commercially available sports drinks contain 6-10% carbohydrate, of which high glycaemic index sources such as glucose and maltodextrin typically represent the primary constituents. Whilst this practice is often adopted without question, differences in the physiological responses elicited when carbohydrate is consumed at rest compared with during exercise mean that transient declines in blood glucose concentrations have been observed during the early stages of the second-half when such solutions are ingested before and during (i.e., including at half-time) soccer-specific exercise[7-9] . In a review of this area, Hills and Russell[7] proposed four modifications to current half-time practices, that may each have merit when seeking to maintain blood glucose concentrations following the resumption of match-play, and thus potentially benefit cognitive and skilled performance throughout the second-half.

1. Changing the glycaemic index of the carbohydrate consumed • May promote a lower insulinaemic response, slower delivery of glucose into the systemic circulation, and may help to spare muscle glycogen

2. Changing the timing of carbohydrate ingestion • Consuming carbohydrate within ~5 min prior to the onset of the second-half may elicit comparable blood glucose responses to when consumed during exercise 3. Changing the amount/concentration of carbohydrate consumed • Ingesting solutions of >10% carbohydrate may afford ergogenic effects on second-half physical and skilled performance

4. Consuming carbohydrate during a half-time rewarm-up • Combining high-intensity rewarm-up exercise with carbohydrate ingestion may attenuate the exercise-induced rebound hypoglycaemic response at the onset of the second-half

This article is not intended to dictate the practices of any football team, player, or practitioner. Such specifics will be, and should be, determined by individual practitioners based upon their own priorities, resources and circumstances. However, the foregoing commentary has highlighted three emerging areas of research, the principles of which warrant deeper consideration amongst those seeking to continually evolve their practice in light of current evidence, and thus move towards ‘optimising’ the preparation of their players. Acknowledging that practical, logistical, and regulatory barriers to implementation exist, given recent advances in player monitoring techniques and the traction gained by the concept of ‘marginal gains’, the days of ‘one-size fits all’ are surely in the past.

Dr Mayur Ranchordas is a Reader in Nutrition and Exercise Metabolism at Sheffield Hallam University and provides performance nutrition consultancy to elite and professional athletes. Mayur’s research is focussed on performance nutrition strategies that can enhance performance and recovery and he also works as a performance nutrition consultant at Wolverhampton Wanderers Football Club. Twitter @Diet4Sport

1. Hills SP, Barrett S, Russell M. Spotlight on substitutes. Football Medicine and Performance Magazine. 2019:37-8. 2. Hills SP, Barrett S, Feltbower RG, Barwood MJ, Radcliffe JN, Cooke CB, et al. A match-day analysis of the movement profiles of substitutes from a professional soccer club before and after pitch-entry. PloS one. 2019;14:e0211563. 3. Hills SP, Barwood MJ, Radcliffe JN, Cooke CB, Kilduff LP, Cook CJ, et al. Profiling the responses of soccer substitutes: A review of current literature. Sports Med. 2018;48:2255-69. 4. Hills SP, Radcliffe JN, Barwood MJ, Arent SM, Cooke CB, M R. Practitioner perceptions regarding the practices of soccer substitutes PloS one. 2019;Under Review. 5. White A, Hills SP, M. H, Cooke CB, Kilduff LP, Cook CJ, et al. The movement demands of professional soccer goalkeepers in different training types and transiently throughout matchplay. J Sports Sci. 2019;In Press. 6. Ranchordas MK, Dawson JT, Russell M. Practical nutritional recovery strategies for elite soccer players when limited time separates repeated matches. J Int Soc Sports Nutr. 2017;14:35. 7. Hills SP, Russell M. Carbohydrates for soccer: A focus on skilled actions and half-time practices. 2018;10:e22. 8. Russell M, Benton D, Kingsley M. Influence of carbohydrate supplementation on skill performance during a soccer match simulation. J Sci Med Sport. 2012;15:348-54. 9. Russell M, Benton D, Kingsley M. Carbohydrate ingestion before and during soccer match play and blood glucose and lactate concentrations. J Ath Train. 2014;49:447-53.