Combined findings from 34 studies
In Souza and colleagues’ meta-analysis of 34 studies, a single intake of caffeinated energy drinks was associated with favourable results in some measures of muscle strength, muscular endurance, endurance testing and jumping performance.
A 5 km run
In Prins and colleagues’ randomised, double-blind study, 18 recreational endurance runners completed a 5 km run approximately half a minute faster on average after consuming 500 ml of an energy drink than after a placebo.
A cycling time trial
In Ivy and colleagues’ 2009 study, 12 trained cyclists completed a simulated time trial faster after consuming 500 ml of an energy drink than after a placebo, without an increase in perceived exertion.
Lane keeping and sleepiness
In Mets and colleagues’ 2011 simulated motorway driving study, 250 ml of an energy drink reduced participants’ sleepiness and improved lane keeping. It does not replace rest.
Alertness in a driving simulator
In Reyner and Horne’s 2002 controlled simulator study, the tested energy drink reduced sleepiness during driving and improved alertness.
Simulator results do not mean that driving while tired is safe; if you feel sleepy, stop and rest.
Reaction time and physical performance
In Chtourou and colleagues’ 2019 randomised, double-blind study, the tested energy drink improved reaction time and some measures of short-term maximal physical performance in 19 male physical education students.
Memory and speed of attention
In Scholey and Kennedy’s 2004 controlled study, the tested drink improved some measures of secondary memory and speed of attention compared with a placebo.
Physical and cognitive results
In the 2001 studies by Alford, Cox and Wescott, some measures of physical and cognitive performance were more favourable after consumption of the tested energy drink than under the control conditions.