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It is well known that the effects of caffeine intake on the central and peripheral nervous system have positive effects on psychomotor function performace. However, studies examining the effects of caffeine on reactive agility are limited in the literature. The main purpose of this study was two fold: 1) to evaluate the effects of acute caffeine ingestion on reactive-agility performance, 2) to examine the effect of acute caffeine use on HRpeak values. A total of 49 healthy, physically active students (nM=25; nF=24) who were studying at Faculty of sports sciences attended the research (xāge = 21.8±2.3 years, xH = 165.6±8.5 cm, xBM = 60.1±10.2 kg). Following familiarization session, all participants was attended to Agility Star Drill Test (ASDT). ASDT was repeated three different times, 48h apart. During each trial, participants consumed 4 mg/kg either regular instant coffee (CAF), or a decaffeinated instant coffee (PLA). While measuring the baseline, the participants were not given any coffee or caffeine-containing food and beverage. Friedman test and Mann-Whitney U tests were used in the analysis of the data. The significance value was accepted as p<0.05. The primarly result of the study showed that caffeine was more effective in reactive-agility test reaction time (RT), than base results (p<0.05), but it was not different than PLA. Secondly, there were no differences in HRpeak values between the trials (p>0.05).
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1 Şırnak University, School of Physical Education and Sport, Şırnak, Turkey
2 Yozgat Bozok University, Faculty of Sport Science, Yozgat, Turkey
Azize Bingöl Diedhiou and Hülya Andre
UDC 796.011.5:178
It is well known that the effects of caffeine intake on the central and peripheral nervous system have
positive effects on psychomotor function performace. However, studies examining the effects of caffeine on
reactive agility are limited in the literature. The main purpose of this study was two fold: 1) to evaluate the
effects of acute caffeine ingestion on reactive-agility performance, 2) to examine the effect of acute caffeine
use on HRpeak values. A total of 49 healthy, physically active students (nM=25; nF=24) who were studying at
Faculty of sports sciences attended the research (x̄age = 21.8±2.3 years, x̄H = 165.6±8.5 cm, x̄BM = 60.1±10.2
kg). Following familiarization session, all participants was attended to Agility Star Drill Test (ASDT). ASDT
was repeated three different times, 48h apart. During each trial, participants consumed 4 mg/kg either
regular instant coffee (CAF), or a decaffeinated instant coffee (PLA). While measuring the baseline, the
participants were not given any coffee or caffeine-containing food and beverage. Friedman test and Mann-
Whitney U tests were used in the analysis of the data. The significance value was accepted as p<0.05. The
primarly result of the study showed that caffeine was more effective in reactive-agility test reaction time (RT),
than base results (p<0.05), but it was not different than PLA. Secondly, there were no differences in HRpeak
values between the trials (p>0.05).
Keywords: agility, blazepod, caffeine, reaction time, reactive agility
Caffeine is one of the most widely consumed psychoactive ingredient foods and supplements in the
world (Frary, Johnson, & Wang, 2005; Ferré, 2008; Fulgoni III, Keast, & Lieberman, 2015). Caffeine has
been of great interest for many years as it has been proven to support cognitive development. One of the
most important cognitive effects is that it reduces reaction time (RT) in activities that require speed. (
Grosch, 1998; Haskell, Kennedy, Wesnes, & Scholey, 2005; Childs & de Wit, 2006). The effects of caffeine
on performance are linked to both central and peripheral mechanisms. Caffeine is associated with the
blockage of adenosine receptors in the central nervous system, which prevents reduction of neural
activity and increases muscle recruitment (Bazzucchi, Felici, Montini, Figura, & Sacchetti, 2011).
Peripherally, caffeine inhibits phosphodiesterase activity, thereby promoting plasma catecholamine and
glycolysis activity, increasing the energy availability of active muscles during exercise (Davis & Green,
2009). As a result of its central and peripheral effects, caffeine provides an increase in psychomotor
function performance such as agility and attention (Brice & Smith, 2001; Gillingham, Keefe, & Tikuisis,
2004; Tikuisis, Keefe, McLellan, & Kamimori, 2004; van Duinen, Lorist, & Zijdewind, 2005).
Studies conducted today, reveal that cognitive factors such as visual scanning, intuition, perception
and decision making are very important for agility, as well as physical characteristic such as speed,
change of direction and strength. ( Zemková, 2016; Armstrong & Greig, 2018). Agility, which is classified
in different ways by researchers, argues that cognitive factors have a key role in this concept, especially in
new approaches. ( Zemková, 2016; Greig & Naylor, 2017; Armstrong & Greig, 2018). Researchers say that
the methods used to evaluate agility performance mostly measure speed and change of direction
performance, therefore they are insufficient to measure all factors that meet this concept, especially
cognitive factors (Šimonek, Horička, & Hianik, 2016; Zemková, 2016; Zouhal et al., 2018). A model was
created by Young, James, & Montgomery (2002) to represent the sub-components of agility performance.
This model was later adapted by Young & Sheppard (2006) with minor changes (Sheppard & Young,
Figure1. Universal agility components (Sheppard & Young, 2006)
According to The European Food Safety Authority, 75 to 150 mg caffeine intake increases alertness
and attention (EFSA Panel on Dietetic Products & Allergies, 2011). There are many studies investigating
the effects of caffeine on agility, RT and speed (Brice & Smith, 2001; Judelson et al., 2005; Lorino, Lloyd,
Crixell, & Walker, 2006; Duvnjak-Zaknich, Dawson, Wallman, & Henry, 2011; Schuda, Thornton, Vitale,
Wright, & Ameres, 2019; Egesoy & Öksüzoğlu, 2020;). However, as mentioned above, agility is not
dependent on a single parameter, on the contrary, it is a feature consisting of many components. In this
regard, to investigate the effects of caffeine on agility, the BlazePod-Agility Star Drill Test (ASDT), which
simultaneously evaluates the RT, speed, visual scanning, and detection features that affect agility, was
applied. In this study, we focused on examining the effect of caffeine on agility, using a higher amount of
caffeine than EFSA claims. In this contex, the aim of this investigation was to find out whether ingestion of
caffeine in the form of instant coffee exerts any influence on agility time performance and observe HRpeak
values of participants during ASDT trials. We hypothesize that ingestion of caffeine in the form of instant
coffee exerts improve reactive-agility performance in physically active individuals.
A total of 49 healthy, physically active students (nM=25; nF=24) who were studying at Faculty of sports
sciences attended the research (x̄age=21.8±2.3 years, x̄H=165.6±8.5 cm, x̄BM=60.1±10.2 kg). Subjects were
recruited by personal contact. Individuals regularly ingesting greater than 600 mg of caffeine per day
were excluded. Prior to data collection, the University approved all procedures and subjects provided
written informed consent. Throughout testing, procedures adhered to standard national and
international regulations regarding the use of human subjects in research.
The cross-over double-blind experiment included a familiarization day with the tests and three
identical experimental trials. In familiarization day, before the study was conducted, participants were
reminded to restrain from all caffeine sources and supplements 48h before the trials and until the end of
the experiment. They were encouraged to train for, avoid alcohol consumption, be adequately hydrated
and sleep at least 8h the day before the experiments. During each trial, participants consumed 4 mg/kg
either regular instant coffee (CAF), or a decaffeinated instant coffee (PLA) from the same manufacturer
(Nestle Nescafe Gold, Bursa, Turkey). While measuring the baseline, the participants were not given any
coffee or caffeine-containing food and beverage. Upon arrival to the laboratory the anthropometric
characteristics of the participants were measured. Participants were then requested to experiment ASDT
for familiarization, one week before the trials and just one time. On the 1st day participants' baseline
values of ASDT were measured. On the 2nd and 3rd trials, the participants applied the test after consuming
coffee with caffeine (CAF) or non-caffeinated (PLA). Heart rate (HR) were measured (Polar Team 2
telemetric system, Finland) before and during the ASDT. For measurement of resting HR, before the
ASDT, participants were asked to lie comfortably in a supine position and HR was recorded. The highest
HR value during the ASDT was recorded as HR
. On the days of CAF and PLA, the coffee were given to
the participants 60 minutes before the test. Caffeine was mixed with 200 ml of hot water at a rate of
of participants and has been given as of sugar free. Decaffeinated coffee given as PLA was given in
proportion to the amount of caffeinated coffee for each participant. Immediately after testing, participants
wer asked to rate their perceived exertion (RPE).
Figure2. Test Protocol
RT of volunteers were measured using the BlazePod Trainer Device (Play Coyotta Ltd., Tel Aviv,
Israel). The intraclass coefficient values displayed excellent reliability (r’s ranging from 0.833 to 0.884).
Five pods were placed around the home base pod on the floor. They were approximately 3 m from each
surrounding pod to the base pod. For each participant the measurement started when the researchers
manually touched the "start now" button on the BlazePod phone application. After the start command,
with the end of the "3-2-1-go" warning sound, the sensors started to flash randomly for 60 sec. For the
starting position, participants were asked to stand next to the home base pod and when a surrounding
pod lights up run to tap it out and then run back as quickly as possible to tap out the home base pod.
Participants repeated this action up to the end of the test time.
Figure3. BlazePod-Agility Star Drills Test
Statistical analysis
Descriptive statistics for the variables used in the analysis of the data are shown as mean and standard
deviation. Normality tests of the variables were performed with the Kolmogorov–Smirnov test and it was
observed that the data were not normally distributed. Friedman test and Mann-Whitney U tests were
used in the analysis of the data. The significance value was accepted as p<0.05.
In Table 1 the mean values of age, height, BM and BMI of the participants’ by gender and total mean
values are presented.
Table1.Descriptive statistic of participants
GenderNx̄age±SD(years)x̄H±SD(cm)x̄BM±SD(kg)x̄BMI ±SD
Female24 21.4±2.5 159.5±5.54 54.66±7.7 21.48±2.9
Male25 22.1±2 171.6±6.53 65.4±9.5 21.96±2.3
Total49 21.8±2.3 165.6±8.5 60.1±10 21.73±2.6
Legend:N number, H height, BM body mass, BMI body mass index
Table2.Results of the participants in different variables for BASE, CAF and PLA trials
x̄±SD x̄±SD x̄±SD
HR74.4±13.2 73.7±14 70±11 2.65 .265
HRpeak188.5±9.8 187.8±10 187±8.8 4.33 .114
NH16.28±1.5 16.63±1.6 16.51±1.8 4.18 .123
RT2.22± 0.20** 2.17±0.27** 2.21±0.26 8.61 .013*
RPE7±1.7 7.3±1.7 7.3±1.5 2.10 .349
Legend:CAF- caffeine, PLA placebo, HR Heart rate, HRpeak peak heart rate, NH number of hits, RT reaction
time, RPE rated perceived exertion
** Trials with a statistically significant difference
Table 2 shows that there is no statistically significant difference in HR, HRpeak, NH and RPE values of
the participants between BASE, CAF and PLA trials (p>.05). However, in RT values of participants there is
a statistically significant difference between trials (p<.05). This difference occurs between CAF and BASE
in favor of CAF trial.
Table3.Results of the participants by gender in different variables for BASE, CAF and PLA trials
HRF73.66±13.93 -.55 .582 69.58±13.63 -1.7 .076 68.83±12.84 -.96 .336
M75.24±12.79 77.73±13.54 71.15±10.5
HRpeakF187.66±10.88 -.25 .802 186.54±12.86 -.42 .674 184.62±10.94 -1.7 .076
M189.3±8.86 189.±6.43 189.32±5.60
NHF15.1±.9 -5.10 .00* 15.7±1.1 -3.8 .00* 15.3±1.2 -4.2 .00*
M17.4±1.2 17.5±1.4 17.6±1.7
RTF2.37±0.16 -4.93 .00* 2.31±0.29 -4.1 .00* 2.34±0.22 -3.7 .00*
M2.08±0.13 2.03±0.14 2.07±0.22
RPEF6.95±2 -.152 .87 7.37±1.71 -.05 .95 7.45±1.69 -.68 .49
M7±1.5 7.4±1.7 7.2±1.4
Legend:CAF- caffeine, PLA placebo, HR Heart rate, HRpeak peak heart rate, NH number of hits, RT reaction
time, RPE rated perceived exertion
* Trials with a statistically significant difference
In Table 3 the mean values of HR, HR
peak, NH, RT and RPE of the participants by gender and
comparison of trials are presented. According to gender comparison there was not statistically significant
difference in HR, HRpeak and RPE values (p>.05), while there was statistically significant difference in NH
and RT values for BASE, CAF and PLA trials (p<.05). When the mean values are examined, it is seen that
this difference was in favor of male participants.
The primary findings of this study are: CAF was more effective in RT during the ASDT than base
results and there was no difference in HRpeak values between trials. Given the specific testing parameters
and research frame of reference, these results suggest that in healthy, rested individuals, consumption of
caffeinated foods and beverages may have an positive effect on reactive-agility.
In the study of Lee et al. (2014) in which they investigated the effect of caffeine on agility T-test result
(6 mg/kg gelatin capsules), no statistically significant difference was found between the agility T-test
results of CAF+PLA and PLA+PLA groups (p>0.05). In another study, in which participants were given
200 mg of caffeine and placebo (Kaczka et al., 2021), no significant difference was found between the
trials in reactive Y-Agility test results (p=0.06). It is well known that caffeine ingestion in doses between
32 and 300 mg improves key aspects of cognitive performance such as attention, alertness, and RT (Snel,
Lorist, & Tieges, 2004; Lorist & Snel, 2008; Nehlig, 2010). However, the limitation of most of the current
studies which is investigating the effect of caffeine intake on agility performance is the use of preplanned
stimuli. It is thought that the participants did not test the effect of reactive-agility in synchronization with
a perceptual component that requires the initiation of movement in a game environment. It should be
noted that while there is general consensus that caffeine improves "low" cognitive functions such as
simple RT, caffeine's effects on "higher" cognitive functions such as problem solving and decision making
are often debated (Gazzaniga, 2000). The ASDT used in the current study included speed, visual reaction
and agility components together, which are the basic components that should be included in agility tests.
Therefore, when compared with many studies in which reactivated agility is tested, it can be said that the
current study tests agility ability similar to the game environment (reaction to unplanned stimuli).
RT values of the current study were examined according to the gender difference. A statistically
significant difference was found for BASE, CAF and PLA trials, and this difference was in favour of male
participants. However, the fact that this difference was seen in the base trial shows that there is a
significant difference between both genders regardless of the CAF and PLA trials. For this reason, the
mean values of CAF and PLA trials were compared with BASE to control the effect on genders. In this case,
it was seen that female participants are more affected by CAF and PLA trials than male participants and
RT decreases more than male participants (F vs. M respectively: CAF: -2.53% vs -2.40% PLA: -1.26% vs -
Previous studies show that caffeine has the effect of promoting sympathetic stimulation (Corti et al.,
2002), which also occurs during physical exercise (Nishijima et al., 2002). However, in this current study
HRpeak results of the participants were examined, and there was not statistically significant difference
between the trials. In the meta-analysis study by Benjamim et al. (2020) they report that the difference in
HRpeak is due to CAF supplementation and not due exercise performance. On the other hand, Gonzaga,
Vanderlei, Gomes, & Valenti (2017), Nelson, Biltz, & Dengel (2014) and Kliszczewicz et al. (2018), they
reported that no difference was found in trials in HRpeak values. Considering the studies in which caffeine
HRpeak changes were not observed, it is thought that adequate cardiovascular stress did not occur in the
study protocols. In the current study, the reason why no difference was observed in HRpeak values
between trials may be due to the absence of cardiovascular stress. Studies investigating the effects of
caffeine on HR still seem to have not reached a consensus.
In a conclusion CAF was more effective in RT during the ASDT than base results and there was no
difference in HRpeak values between trials and genders.
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Full-text available
Evaluating different doses of caffeine (CAF) on heart rate (HR) variability (HRV) during and following exercise in order to assess its impact on autonomic control. We intended to evaluate the influence of CAF as a supplement before exercise on HRV through a systematic review. Manuscripts were selected based on electronic searches of MEDLINE, EMBASE and CINAHL databases from 2010 to 2019 and followed the protocol Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA). Blind randomized designs and controlled trials that reported the influence of CAF on HRV during exercise and during recovery from exercise, with strength of evidence assessed using the GRADE system; the search for the studies was organized using the PICOS strategy. A total of 1797 articles were recognized, following the screening and eligibility stages, 9 studies continued to the final sample. Six studies reported that the combination of CAF supplementation with physical exercise exhibited higher HR when compared to the placebo group during post-exercise recovery; additionally, prolonged activation of sympathetic cardiac control and delayed parasympathetic reactivation following exercise was observed. However, three studies demonstrated no CAF influence when using similar doses. This review observed equivocal results in HR and HRV recovery following exercise with the presence of CAF consumption. These findings cannot confirm the cardiac autonomic changes observed where entirely due to the influence of CAF, and further studies should be performed to better understand this relationship. • KEY TEACHING POINTS • CAF increased HR during exercise and throughout the recovery period. • CAF prolonged post exercise sympathetic activity. • CAF delayed vagal reactivation. • Deviations in HRV and HR are dependent on the combination of three main factors: CAF dosage, type of exercise, and cardiorespiratory fitness.
Full-text available
Background: The purpose of this study was to examine the resting cardiac autonomic nervous system's response to the ingestion of a complex containing Citrus aurantium + Caffeine (CA + C) and its influence on recovery following a high-intensity anaerobic exercise bout in habitual caffeine users. Methods: Ten physically active males (25.1 ± 3.9 years; weight 78.71 ± 9.53 kg; height 177.2 ± 4.6 cm; body fat 15.5 ± 3.13%) participated in this study, which consisted of two exhaustive exercise protocols in a randomized crossover design. On each visit the participants consumed either a CA + C (100 mg of CA and 100 mg of C) or placebo (dextrose) capsule. After consumption, participants were monitored throughout a 45-min ingestion period, then completed a repeated Wingate protocol, and were then monitored throughout a 45-min recovery period. Cardiac autonomic function (Heart Rate (HR) and Heart Rate Variability (HRV)) and plasma epinephrine (E) and norepinephrine (NE) were taken at four different time points; Ingestion period: baseline (I1), post-ingestion period (I2); Recovery period: immediately post-exercise (R1), post-recovery period (R2). Heart rate variability was assessed in 5-min increments. Results: A repeated measures ANOVA revealed significant time-dependent increases in HR, sympathetic related markers of HRV, and plasma E and NE at I2 only in the CA + C trial (p < 0.05); however, no meaningful changes in parasympathetic markers of HRV were observed. Participants recovered in a similar time-dependent manner in all markers of HRV and catecholamines following the PLA and CA + C trials. Conclusion: The consumption of CA + C results in an increase of sympathetic activity during resting conditions without influencing parasympathetic activity. CA + C provides no influence over cardiac autonomic recovery.
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Introduction: Laterality (i.e., handedness, footedness, and eyedness) could have an impact on highly repeated soccer movements and thus, could influence performance. The purpose of this study was to examine the laterality of high-level football players and its effects on 180° left and right U-turn movements. Materials and Methods: Handedness, footedness, and eyedness were determined in 72 elite football players (EFP, 18.2 ± 2.2 years) from the Stade Rennais Football Club (French League 1) and 9 amateur football players (AFP, 19.6 ± 2.1 years). Players performed a visual-motor task on a synthetic pitch consisting of 180° left and right rotations as fast as possible in response to a visual light on a computer screen. Movement times and reactive times for each left and right rotation were recorded with an accelerometer and video display. Results: Laterality profiles showed a majority (χ² = 9.42, df = 2, p = 0.031) of crossed formulas (i.e., dominant leg or hand is controlateral to the dominant eye) for EFP (53 ± 7%) and a majority of non-crossed formulas for AFP (63 ± 9%). Reaction times were significantly faster (p = 0.028, effect size = 0.148, trivial) in EFP right-eyed (568.2 ± 55.5 ms) than in AFP (610.0 ± 43.9 ms). For the left rotation and for right-footed players, movement times were significantly different (p = 0.043, effect size = 0.413, small) between EFP (1.15 ± 0.07 s) and AFP (1.17 ± 0.07 s). A significant difference (p < 0.033) was observed between footedness and rotation movement times in the EFP. Conclusion: Our results showed that laterality profiles differed between EFP and AFP. Hence, in EFP, reaction times depended on the side of the visual stimulus. Moreover, leg laterality of EFP influenced 180° left or right rotation speed. Our results indicate the importance of determining laterality in soccer players and identifying deficits in performance when turning.
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The post-exercise recovery period is associated with changes in autonomic modulation, which can promote an intercurrent-favorable environment. Caffeine has the ability to release catecholamines, but its effects after exercises is little explored. The present study aims to evaluate the acute effects of caffeine on the autonomic control and cardiorespiratory parameters after moderate intensity aerobic exercise. 32 young males (23,59 ± 3,45 years) were submitted to two protocols: Placebo and Caffeine, consisting of 15 minutes of rest, 30 minutes of exercise on a treadmill to 60% on VO2peak, followed by 60 minutes of recovery. Heart rate variability indices and cardiorespiratory parameters were determined at different times during the protocols. The RMSSD and SD1 indices recovered faster in placebo (p < 0.05). The systolic blood pressure differences were found from the 1st to the 5th minute of recovery with the caffeine protocol and from the 1st and 3rd minute with the placebo, whereas, for diastolic blood pressure, significant differences (p < 0.0001) were observed only for the caffeine protocol at the 1st and 3rd minutes of recovery. Caffeine was shown to be capable of delaying parasympathetic recovery but did not influence the behavior of the respiratory rate, oxygen saturation or frequency-domain HRV indices.
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This study estimates the contribution of reaction time and movement velocity to the reactive agility time while covering varied distances. A total of 95 athletes of karate, hockeyball and soccer participated in a simple reaction, two choice reaction, step initiation and reactive agility test. Agility time was significantly better in karate-kumite than karate-kata practitioners when covering a distance of 0.8 m (8.2%, Reaction time and movement velocity differentially contribute to the agility time in athletes of varied specializations. This reflects their specific demands on agility skills, and therefore should be addressed in agility testing in order to identify an athlete’s weakness.
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Background: Authors in their contribution point to the differences in the methods of measurement of agility in the practice. Based on the experience of coaches as well as on their own experience have come to the conclusion that the Illinois Agility Test, which has long been used for the testing of agility in fact does not measure perception abilities and decision-making processes, since motor activity performed during the testing procedure represents a closed skill, where the only task of the tested person is to accelerate, decelerate and change the direction of running, while the task is known in advance. On the contrary, some authors recommend the testing of agility using apparatuses measuring selective reaction, such as Fitro Agility Check. Objective: The aim of the research was to find out differences in the performance of players from the point of view of sport specialization and also to assess the relationship between the performance of players in two agility tests (Illinois Agility Test, measuring the ability of simple reaction, acceleration, deceleration and changes of movement direction, as well as Fitro Agility Check, measuring the above mentioned processes plus the ones of perception and decision-making). Methods: The sample comprised basketball (G1), volleyball (G2) and soccer (G3) players (N = 55 boys, Mage = 15.78 years, age range = 14-17 years) from sport clubs in Slovakia. Illinois Agility Test (IAT) was used for testing acceleration and deceleration speed, simple reaction as well as changes of direction. Time of the trial was recorded by Microgate photocells. Fitro Agility Check (FAC) was used for the testing of reactive agility. Differences between independent groups were assessed using Kruskal-Wallis H test, or Mann-Whitney U test. Non-parametric Spearman correlation coefficient was used for detecting whether any correlation between the two variables exists (results in FAC vs IAT). Results: The greatest differences were found between the performances of players in IAT, on the contrary in the test FAC we found agreement in performances of players of different specializations. The value of statistical significance (p = .774) point to the non-existence of a relationship between the performance in IAT vs FAC and stress fundamental difference between both variables. Conclusions: This study provides evidence supporting the experience of coaches that when developing agility it is inevitable to transfer from performing exercises with the change of direction planned in advance realized in static conditions onto the practice of open skills, in which reaction to the changing conditions of the match is combined with anticipation of the resulting optimum solution of the given situation.
Conference Paper
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We studied the role of caffeine in action monitoring as expressed by the error-related negativity (ERN), an event-related brain component that reflects anterior cingulate cortex (ACC) activity. In a double-blind, placebo-controlled, within-subjects experiment, two caffeine doses (3 and 5 mg/kg BW) and a placebo were dissolved in a cup of decaffeinated coffee and administered to 15 habitual coffee drinkers. Compared with placebo, both caffeine doses enlarged the ERN. The P2 and P3 amplitudes were not affected by caffeine. Thus, the enlarged ERN after caffeine reflects a specific effect on action monitoring. We conclude that consumption of a few cups of coffee intensifies central information processing, specifically the monitoring of ongoing cognitive processes for signs of erroneous outcomes. We also studied the effects of caffeine on task switching in alternated task (AABB) blocks and single-task (AAAA) blocks. Participants alternated between two tasks (A and B) in a predictable manner. Reaction time switch costs were reduced compared to placebo. ERPs revealed a negative deflection that developed within the preparatory interval, which was more negative for switch compared to repeat trials. This switch-related difference was increased under caffeine compared to placebo. These results suggest that a few cups of coffee improve task-switching performance by enhancing anticipatory processing such as task-set updating.
Objectives Agility is a functional requirement of many sports, challenging stability, and commonly cited as a mechanism of injury. The Functional Movement Screen (FMS) and modified Star Excursion Balance Test (mSEBT) have equivocally been associated with agility performance. The aim of the current study was to establish a hierarchical ordering of FMS and mSEBT elements in predicting T-test agility performance. Design Cross-sectional study design. Setting: University. Participants: Thirty-two female rugby players, 31 male rugby players and 39 female netballers. Main Outcome Measures: FMS, mSEBT, T-test performance. Results The predictive potential of composite FMS and mSEBT scores were weaker than when discrete elements were considered. FMS elements were better predictors of T-test performance in rugby players, whilst SEBT elements better predicted performance in netballers. Hierarchical modelling highlighted the in-line lunge (ILL) as the primary FMS predictor, whereas SEBT ordering was limb and sport dependent. Conclusions The relationship between musculoskeletal screening tools and agility performance was sport-specific. Discrete element scores are advocated over composite scores, and hierarchical ordering of tests might highlight redundancy in screening. The prominence of the ILL in hierarchical modelling might reflect the functional demands of the T-test. Sport-specificity and limb dominance influence hierarchical ordering of musculoskeletal screens.
Background: Agility is a fundamental performance element in many sports, but poses a high risk of injury. Hierarchical modelling has shown that eccentric hamstring strength is the primary determinant of agility performance. Purpose: The purpose of this study was to investigate the relationship between knee flexor and extensor strength parameters and a battery of agility tests. Study design: Controlled laboratory study. Methods: Nineteen recreational intermittent games players completed an agility battery and isokinetic testing of the eccentric knee flexors (eccH) and concentric knee extensors (conQ) at 60, 180 and 300°·s-1. Peak torque and the angle at which peak torque occurred were calculated for eccH and conQ at each speed. Dynamic control ratios (eccH:conQ) and fast:slow ratios (300:60) were calculated using peak torque values, and again using angle-matched data, for eccH and conQ. The agility test battery differentiated linear vs directional changes and prescriptive vs reactive tasks. Results: Linear regression showed that eccH parameters were generally a better predictor of agility performance than conQ parameters. Stepwise regression showed that only angle-matched strength ratios contributed to the prediction of each agility test. Trdaitionally calculated strength ratios using peak torque values failed to predict performance. Angle-matched strength parameters were able to account for 80% of the variation in T-test performance, 70% of deceleration distance, 55% of 10m sprint performance, and 44% of reactive change of direction speed. Conclusions: Traditionally calculated strength ratios failed to predict agility performance, whereas angle-matched strength ratios had better predictive ability and featured in a predictive stepwise model for each agility task. Level of evidence: 2c.
Coffee and tea are traditional sources of caffeine in the diet, but other sources, such as energy drinks, are now available. Because risks and benefits of caffeine use are dose dependent, the public health consequences of caffeine consumption cannot be determined without data on amounts currently consumed by the US population. The objective was to obtain an up-to-date, nationally representative estimate of caffeine consumption in adults. Dietary intake data from NHANES from 2001 to 2010 for adults ≥19 y of age were used (n = 24,808). Acute and usual intake of caffeine was estimated from all caffeine-containing foods and beverages. Trends in consumption and changes in sources of caffeine were also examined. Eighty-nine percent of the adult US population consumed caffeine, with equal prevalence in men and women. Usual mean ± SE per capita caffeine consumption when nonusers were included was 186 ± 4 mg/d, with men consuming more than women (211 ± 5 vs. 161 ± 3 mg/d, P < 0.05). Usual intake in consumers was 211 ± 3 mg/d, with 240 ± 4 mg/d in men and 183 ± 3 mg/d in women (P < 0.05); 46% was consumed in a single consumption event. In consumers, acute 90th and 99th percentiles of intake were 436 and 1066 mg/d, respectively. Consumption was highest in men aged 31-50 y and lowest in women aged 19-30 y. Beverages provided 98% of caffeine consumed, with coffee (∼64%), tea (∼16%), and soft drinks (∼18%) predominant sources; energy drinks provided <1%, but their consumption increased substantially from 2001 to 2010. Although new caffeine-containing products were introduced into the US food supply, total per capita intake was stable over the period examined. © 2015 American Society for Nutrition.