The Influence of Caffeine Expectancies on Simulated Soccer Performance in Recreational Individuals.

Akbar Shabir,Olivia Ensor,Laura Sandford,Mitch Storey,Matthew F Higgins,Andy Hooton,George Spencer,Bryan Saunders,Jason Tallis

doi:10.3390/nu11102289

Abstract

Caffeine (CAF) has been reported to improve various facets associated with successful soccer play, including gross motor skill performance, endurance capacity and cognition. These benefits are primarily attributed to pharmacological mechanisms. However, evidence assessing CAF’s overall effects on soccer performance are sparse with no studies accounting for CAF’s potential psychological impact. Therefore, the aim of this study was to assess CAF’s psychological vs. pharmacological influence on various facets of simulated soccer performance. Utilising a double-dissociation design, eight male recreational soccer players (age: 22 ± 5 years, body mass: 78 ± 16 kg, height: 178 ± 6 cm) consumed CAF (3 mg/kg/body mass) or placebo (PLA) capsules, 60 min prior to performing the Loughborough Intermittent Shuttle Test (LIST) interspersed with a collection of ratings of perceived exertion (RPE), blood glucose and lactate, heart rate and performing the Loughborough Soccer Passing Test (LSPT). Whole-body dynamic reaction time (DRT) was assessed pre- and post- LIST, and endurance capacity (TLIM) post, time-matched LIST. Statistical analysis was performed using IBM SPSS (v24) whilst subjective perceptions were explored using template analysis. Mean TLIM was greatest (p < 0.001) for synergism (given CAF/told CAF) (672 ± 132 s) vs. placebo (given PLA/told PLA) (533 ± 79 s). However, when isolated, TLIM was greater (p = 0.012) for CAF psychology (given PLA/told CAF) (623 ± 117 s) vs. pharmacology (given CAF/told PLA) (578 ± 99 s), potentially, via reduced RPE. Although DRT performance was greater (p = 0.024) post-ingestion (+5 hits) and post-exercise (+7 hits) for pharmacology vs. placebo, psychology and synergism appeared to improve LSPT performance vs. pharmacology. Interestingly, positive perceptions during psychology inhibited LSPT and DRT performance via potential CAF over-reliance, with the opposite occurring following negative perceptions. The benefits associated with CAF expectancies may better suit tasks that entail lesser cognitive-/skill-specific attributes but greater gross motor function and this is likely due to reduced RPE. In isolation, these effects appear greater vs. CAF pharmacology. However, an additive benefit may be observed after combining expectancy with CAF pharmacology (i.e., synergism).

Highlights

Caffeine (CAF) is the most frequently used psychoactive substance in sport, and has been observed to improve various exercise modalities that may benefit soccer performance including: strength and power output [1,2] endurance capacity [3,4,5] and gross motor skill performance [6,7,8]
All treatments enhanced TLIM vs. placebo, synergism resulted in the greatest improvements
We explored changes in Blood Lactate (BLa) and Blood Glucose (BG) concentrations, CAF may influence various other metabolites [88,89] that might contribute to fluctuations in sport and exercise performance

Summary

Introduction

Caffeine (CAF) is the most frequently used psychoactive substance in sport, and has been observed to improve various exercise modalities that may benefit soccer performance including: strength and power output [1,2] endurance capacity [3,4,5] and gross motor skill performance [6,7,8]. Caffeine’s stimulatory properties may improve soccer performance by ameliorating physical and/or cognitive fatigue, which has been observed to reduce the total distance ran (~5%–10%) and frequency of sprints (~3%–4%) between the first and second half of games [11,12,13,14,15,16]. The majority of goals conceded are within the latter stages of halves [17], between min. The least goals are conceded within min 0–15 (12%) and 45–60 (16%) when physical and/or cognitive fatigue is at its lowest or has been somewhat replenished during the half-time interval. Studies directly assessing CAF’s influence on soccer performance remain scarce and those that have done so almost exclusively attribute any benefits to pharmacological mechanisms [3,4,6,7,8]

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