With over 90% of North Americans as regular users, caffeine is the most enjoyed stimulant on the planet. In fact, history dates caffeine use back to cavemen, where they would chew caffeinated seeds, leaves, bark, and plants to give them energy, stamina, and stave off hunger during long treks and hunts. Certainly, we have evolved from the days of cave-dwellers, and so has the way we get our daily caffeine. Today, you can get a quick caffeine pick-me-up from one of many sources— caffeinated energy drinks, pre-workout supplements, caffeinated gum, and caffeine pills to name a few.
Research over the past decade provides compelling support for caffeine ingestion prior to exercise, where it has been most commonly reported to decrease central nervous system fatigue and ratings of perceived exertion—equating to longer and more intense training sessions. Notably, past studies have shown that central fatigue limits performance when exercising in the heat and women tend to experience less central fatigue during exercise than men. Moreover, studies suggest that males tend to be more responsive to preworkout caffeine than women.
A recent study published in Applied Physiology, Nutrition, and Metabolism, compared the impact of caffeine supplementation on exercise capacity and psychological state in young females and males walking briskly to exhaustion in the heat (42 °C/107.6 °F). Based on past data, it was hypothesized that the performance enhancing effects of caffeine on exercise in the heat would be greater in males than females. Congruent with their hypothesis, the researchers found that pre-workout caffeine ingestion (6 mg/kg) decreased ratings of perceived exertion and fatigue in males, but not in females when exercising in high temperatures. Interestingly, caffeine promoted greater increases in HR and blood lactate concentrations during exercise in the heat in both males and females.
ACTION POINT: Overall, it seems that males benefit most from taking caffeine before exercising in the heat; but, this doesn’t mean women cannot benefit from everything else caffeine has to offer (i.e., fat burning, focus, intensity, etc). Although dosing varies from study to study, for safety and efficacy, we recommend taking 200-400 mg of caffeine up to an hour prior to training. If you have never consumed caffeine, start with the lowest dose and work up accordingly. If you exhibit symptoms like shaking, nervousness, heart palpitations, or anxiety then you have taken too much.
Suvi S, Timpmann S, Tamm M, Aedma M, Kreegipuu K, Ööpik V. Effects of caffeine on endurance capacity and psychological state in young females and males exercising in the heat. Appl Physiol Nutr Metab. 2017 Jan;42(1):68-76.