3 capsules of PLACEBO similar to caffeine condition in size and weight

No capsules were given

Rey Auditory Verbal Learning Test: The RAVLT is a neuropsychological assessment designed to evaluate verbal memory. The test is designed as a list-learning paradigm in which the volunteer hears a list of 15 nouns and is asked to recall as many words from the list as possible. The number correct and the number that were given by the participant but not on the list (intrusions) are noted. This process is re-peated 4 more times. The process is repeated but with a second interference list (List B) is presented in the same manner, and the participant is asked to recall as many words as possible from List B and scoring recorded. . After the interference trial, the participant is immediately asked to recall the words from List A, which they heard five times previously and the number of correct words and intrusions are recorded. RAVTL total number, number of dis-tractions and retention are recorded and analysed.

Stroop word-colour interference test. The participants were asked to read out their responses to words or colours for 45 s as quickly as possible and to leave no errors uncorrected. This was filmed and the number of errors and total amount completed was recorded and analysed. The first sheet had text (red, blue, yellow, black and green) in black ink (naming word test, W). The second sheet had blocks of colour corresponding to the text on the first sheet (naming colour test, C). With the third sheet, the participants had to read out the word (which was coloured differently to the word, e.g., the word was yellow and the colour red, referred to as the naming colour of word test, CW) and for the fourth sheet, the participants had to read out the colon (which was wrongly named, e.g., the colour was yellow but the word was red, referred to as the naming of word not colour test, WC). In this fourth sheet, the words were printed in the reverse order to the third sheet.

Mean Skin temperature (Tsk) was assessed simultaneously by skin thermistors (Grant Instruments, Squirrel 2010 series, Shepreth, UK), which were placed at four locations on the left side of the body (chest [ch], forearm [f], thigh [th] and calf [ca]). Duration in each session no longer than 35 mins.

Mean Tsk was calculated as follows:

Tsk = (0.34 x Tch) + (0.33 x Tth) + (0.18 x Tca) + (0.15 x Tf)

The mean body temperature (Tmb) was calculated using skin thermistors from 4 skin sites on the left side of the body (chest [ch], forearm [f], thigh [th] and calf [ca]). : Tmb = (0.64 x Tr) + (0.36 x Tsk)

Morning profile of mood states questionnaire (POMS; Version 32) for moods: vigour, tension, calmness, happiness, confusion, depression and fatigue on a visual analogue scale (0=not at all and 4 = extremely). Each mood is the addition of scores for the 4 questions associated with the mood. ~ 60 s each task.

Sleep questions from the Liverpool Jet lag Questionnaire: get to sleep, how well slept, waking time and alertness after waking. Measured on a -5 (later or worst) to +5 scale (more or earlier) where ZERO is compared to normal.

7-day food diary that was analyzed using Nutritics® analysis software by a SENr registered Sports and Exercise Nutritionist. Data is presented in macro-nutrients and micro-nutrient diet (mg or g).

Habitual caffeine consumption was assessed using the caffeine consumption questionnaire (CCQ), where caffeine intake was assessed in the morning, afternoon, evening and night. Total daily intake was expressed in mg.

No preference to training regarding time-of-day by a weekly self-reported 2-week training diary for type of exercise, duration, intensity and time of day. With time of day of exercise preference recorded.

Extreme chronotype (assessed via the Composite Morningness Questionnaire) to assess morning, intermediate and evening types. Where Evening type scores 22 and less, Intermediate type 22-43 and Morning type 44 and above.

Poor sleep quality (as indicated by the Pittsburgh sleep quality index global score >5).

Depressed mood severity from the Beck depression inventory (BDI).21 questions were answered (with 4 answers, 0= I do not feel and 3 = I am so..). The values summated to scores where 0-9 is minimal depression, 10-18 mild and 19-29 moderate depression. 30-63 sever depression. This takes 60 s to complete.

Caffeine withdrawal symptoms (total score) assesses caffeine withdrawal symptoms. Participants were asked to rate each of the 32 questions in terms of how they were feeling at that moment on a 5-pt. scale from 0 (not at all) to 4 (extremely). Eight of the items are positively worded (e.g., energetic) and were reversed scored prior to analyses. At start and during the protocol.]