Research into various amino acids, stimulants and other ergogenic ingredients has shown that many can have positive acute effects on athletic performance when taken prior to training. Pre-workout formulas typically contain ingredients such as creatine, arginine, beta alanine and caffeine as all of these are well researched into their abilities to enhance performance by either increasing strength, endurance or mental focus and energy. The dosages of these ingredients can vary greatly depending on the main focus of the formula as some are designed primarily to enhance strength whilst others are designed to focus more heavily on stimulating the central nervous system.
The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine . 
Thanks for this post, Matt! What kind of timing do you recommend before a race like a half marathon? I ran VCM on Sunday (I think I might’ve spotted you there last year!). I had some banana and PB like an hour before. It is not the first time I’ve done that, but anyway I ended up with really bad cramping, had to stuff a pile of tums onboard right before the race and had a really tough run. I mean, I clearly had a bug or something, but I want to be like extra careful next time. Hoping to make up for it in Ithaca in June. Any advice? I’m thinking of running on empty. I usually make a little homemade chia gel that I start to sip at mile 5. (I’m vegan, too!)