Caffeine: Caffeine An Effective PED, PWO
TL:DR - caffeine is shown to be performance enhancing, for most people. There are genetic variables, as well as environmental factors that that could cause subjects to not respond under different conditions.
Caffeine is a popular choice for PWO and is known within the bromunity to improve performance. But is that true for all people, and how much does it impact performance, if at all?
The study I am referring to mostly appeared in Sports Medicine in January 2018. Per the report, current guidelines recommend consuming 3-9mg/kg 60min before exercise. That translates to 270mg-810mg for a 90kg (200 pound) person, or roughly 2-5 cups of 8oz coffee.
For some, caffeine is highly ergogenic, or performance enhancing and is a popular choice for professional athletes pre-competition. From 2004 to 2008, 74% of athletes sampled after national or international competitor had levels sufficient to register in a test after a ban on caffeine in competition was lifted. Between 1984 and 2004 caffeine was banned for in-competition use at doses exceeding 12 ug mL.
In a very simplistic explanation caffeine is performance enhancing by reducing the effectiveness of the body in down regulating nervous activity and arousal. It also increases the muscle firing rates, stimulates adrenaline, and decreases pain. You can perform quicker, and go farther.
That said, the performance enhancement results touted of caffeine are based on the mean result, or an estimate of likely responses of each individual within a group. Variation in studies is considerable, with a running trial demonstrating the wide variation of ergogenic response available – ranging from 105% to 205% when compared against the placebo or control group.
The wide range of variation of response is based on genetics, within the gene CYP1A2. There are two variations (for our purposes): individuals with AA homozygotes (fast metabolizers) and C allele carriers (slow metabolizers). The former benefits the most from caffeine in terms of performance enhancement and health benefits, while the latter benefits only a small performance benefit and an increased risk of myocardial infarction and hypertension. Further, those with a genetic variation in adenosine receptors (ADORA2A) can increase anxiety in individuals following caffeine, to an ergolytic, or performance impairing, level as well disrupting sleep and leading to poor recovery. That said, I imagine the increase in anxiety that causes performance impairments is specific to certain activity or a competitive setting - I can’t imagine anxiety impacting my own strength training regimen for example.
There are a ton of other variables that impact how well you might respond to caffeine: smoking, vegetable consumption, fitness level, timing and dose. Habitual use of caffeine induces tolerance, though it’s thought it only increases the dose needed to gain benefit. Anecdotally, I notice this and increase my own consumption of caffeine beyond my standard double shot strategically prior to certain key workouts (e.g. high volume days). Caffeine effectiveness is going to be highly individual and your own experimentation is necessary to determine the right performance enhancing dose for you, but I do conclude the caffeine is almost always effective as a PWO.