Can Caffeine Improve Quadriceps Performance After Eccentric Exercises?
Title: Effect of Caffeine Supplementation on Quadriceps Performance After Eccentric Exercise
Author: Green et al
Journal: Journal of Strength and Conditioning Research (2018)
Objective: To study the effects of caffeine on uninjured and injured muscle
Caffeine is the most commonly used stimulant in the world and provides a wide variety of benefits. Most commonly, it is obtained from drinking coffee or tea. As many as half of athletes use coffee for its performance enhancing potential.
The effects of caffeine on strength are mixed, with some showing benefits and others not. Similarly, research isn’t clear on whether it improves muscle endurance. The most recent large scale study suggests that it helps with strength and endurance compared to placebo. The effects of caffeine on exercise induced muscle damage (EIMD), of which delayed onset muscle soreness (DOMS) is the most common symptom, are not currently known.
Caffeine appears to act as an ergogenic aid via its role as an adenosine agonist and modified pain perception. Caffeine has been shown to reduce pain during cycling and resistance training. The authors of this study wanted to determine the response of injured muscle to caffeine consumption and determine the fatigue resistance of injured muscle after caffeine ingestion.
16 total individuals (8 men, 8 women), physically active
Average age 24, weight 75 kg, body fat 18.2%
One leg was assessed under uninjured and injured (100 eccentric quadriceps contractions) conditions after caffeine supplementation
The other leg assessed under both conditions after placebo supplementation.
Caffeine increased peak isokinetic torque by nearly 7% in uninjured muscle and 9% in injured muscle.
Caffeine had no effect on isometric torque, ratings of soreness or fatigue index compared to placebo
Caffeine appears to help with dynamic muscle contractions in both injured or uninjured states.
In isometric movements where the muscle group is neither shortening or lengthening, this study does not find caffeine helps. Other studies have shown benefit in isometric movements.
How much caffeine masks exercise induced muscle damage or delayed onset muscle soreness is less clear.
My thoughts are that caffeine has a lot of benefits and is clearly ergogenic, so if you want to supplement this is a fairly safe way to do it. The authors of this study used 6 mg per kg.