The benefits of caffeine on long-term endurance performance are well-known . In contrast, it is not understood if caffeine ingestion is ergogenic during short-term high-intensity exercises. It has recently been reported that caffeine causes ergogenic effects when testing muscle endurance, but there is little evidence to sustain caffeine ergogenic effects on maximum strength . We will take a look at a very recent study that attempts to address the effects of caffeine on single all-out muscle contractions .
It has previously been shown that there is an increase in maximum muscle strength and power output with caffeine ingesting in resistance-trained men , and similar results have been found in women . An ergogenic effect of caffeine on muscle power as low as 5%  may influence performance in sports with short-term actions (e.g. football).
During prolonged exercise, the ergogenic effect of caffeine is different from how caffeine affects neuromuscular performance during short-term exercise. Because caffeine could be acting through a different mechanism of action for endurance than for strength-power performance, the dose of caffeine required to activate the mechanism could also differ. No previous research has addressed the dose of caffeine needed to improve strength and power during isoinertial contractions of large muscle groups. Also, there is limited information regarding the side effects of the caffeine doses typically ingested (3-9 mg/kg) for improving sports performance.
The research on caffeine . . .
A very recent well-controlled study sought to find the oral dose of caffeine that improves the voluntary contraction and power of large muscle groups in resistance-trained athletes . This study also examined the side effects linked with a complete range of caffeine doses and their potential implications for the athletes’ performance. Thirteen highly resistance-trained men participated and underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: 1) placebo, 2) 3 mg/kg BW caffeine, 3) 6 mg/kg BW caffeine, and 4) 9 mg/kg BW caffeine). Bar displacement velocity and muscle power output during free weight full squat and bench press exercises were measured against four incremental loads (25%, 50%, 75%, and 90% one-repetition maximum (1RM). Cycling peak power was also measured, and caffeine side effects were evaluated at the end of each trial and 24 hours later.
The results . . .
The following are the key findings of this research:
- Mean velocity at light loads (25%-50% 1RM) increased significantly above placebo for all caffeine doses.
- At a resistance load of 75% 1RM, 3 mg/kg BW caffeine didn’t improve squat or bench press muscle power or bench press velocity.
- A dose of 9 mg/kg BW caffeine was needed to enhance bench press velocity and squat power at the heaviest load (90% 1RM) along with increasing cycling peak power output.
- Regarding side effects, the 9 mg/kg BW caffeine drastically increased the frequency of the adverse side effects (15-62%).
The chief finding of this research is that caffeine significantly improves movement velocity under all loading conditions (from 25% to 90% 1RM) in both the upper and lower body musculature. The heavier the load, and thus the longer time available to apply force, the higher the caffeine dose needed to achieve an ergogenic effect.
The ergogenic effect of caffeine against the lighter loads (25%-50% 1RM) was maximal with a low dose of caffeine (3 mg/kg). In contrast, higher caffeine doses were needed to improve performance against heavier loads (6 mg/kg for 75% 1RM and 9 mg/kg for 90% 1RM). This seems to dictate that the dose of caffeine will depend on the resistance that the athlete has to overcome.
A key finding was that there was an increase in gastrointestinal problems, anxiety, and headaches that remained 24 hours after the trial in doses at or higher than 6 mg/kg. The presence of negative side effects increased markedly with the 9 mg/kg dose of caffeine
The practical application for performance is that muscle contractions against heavy loads (75%-90% 1RM) also require a high caffeine dose (9 mg/kg) to obtain an ergogenic effect. However, explosive, high-velocity low-resistance actions require a much lower caffeine dose (3 mg/kg), thus avoiding the undesirable side effects.
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