Caffeine (1, 3, 7-trimethylxanthine) which can be ubiquitously found in energy drinks, sodas, coffee, and supplements, is one of the principal legal drugs consumed worldwide. Caffeine based ergogenic aids are utilized prolifically within training and competition for an ergogenic benefit to enhance sporting performance by both recreational and elite athletes. The evidence of caffeine's ability to enhance endurance performance is well established, however, evidence of an ergogenic benefit for muscular endurance and strength-based tasks is limited. Moreover, the limited evidence for caffeine's ergogenic benefit in muscular endurance and strength is equivocal, and therefore, practical recommendations for the implementation of caffeine supplementation in training and competition for coaches, and practitioners is difficult. Indeed, it is currently not known if, and how caffeine may improve muscular endurance and/or strength based tasks. Variability in the findings could be due to several factors including muscles tested, participant characteristics, exercise protocol, type and dose of caffeine used. This brief review will discuss the current literature relating to the potential efficacy of caffeine to enhance muscular endurance and strength based performance, and provides evidence based recommendations for athletes and coaches to implement. attempt to aid recreational performance . This has promoted an increase in the sale of caffeine based supplements and energy drinks  and these readily available forms of the drug are now typically consumed by younger populations and even those not participating in sport or exercise . In a sport and exercise context, caffeine has been consistently shown to aid a variety of endurance based tasks [5-7] with significant enhancements in cycling [8,9], swimming  and rowing  performance all being reported. On the other hand, both supporting [12-18] and contradicting [19-23] research has been published in terms of muscular endurance. Furthermore, the evidence of caffeine improving muscular strength is a concept that produces additional equivocal conclusions. Few studies have reported increases in one repetition maximum (1RM) post caffeine supplementation in comparison to placebo [21,23] and control  trial with a superior number reporting no change [20,25,26]. Caffeine's primary mechanistic process likely occurs through the antagonising of adenosine . This process is achieved by caffeine binding to adenosine receptors, reducing adenosine's ability to slow neural activity, reduce arousal, and induce sleep . Further rewards from caffeine's effect on adenosine receptors include enhanced neurotransmitter release, increased firing rates, and amplified spontaneous and evoked potentials . Caffeine has also been shown to alter metabolic substrate utilization  and provide enhanced fat oxidation and consequential glycogen sparing . Alterations to pain perception following caffeine supplementation have also been reported  most likely due to enhanced secretion of β-endorphins . More specifically to strength performance, possible mechanisms also include increased muscle activation , motor unit recruitment , and enhanced excitation contraction coupling . It should be noted, that it is beyond the scope of this review to provide a comprehensive overview of the mechanisms of caffeine. The primary purpose of this review is to provide in depth analysis of the evidence relating to the use of caffeine in muscular endurance and strength based exercise, and provide coaches and athletes, at both elite and recreational level, with recommendations for the use of caffeine with regards to muscular strength and muscular endurance. For a complementary, wider-ranged review of all current literature, readers is direct to other published review articles [36,37] and a meta-analysis .