Eccentric Knee Strength and Coffee

I don’t know about you, but as soon as my feet are on the ground in the morning, my body is on autopilot to the coffee machine.  It does not matter if what I am doing that day, I can not function without a cup of coffee.  Caffeine is always a hot topic when it comes to athletes, there was even a time that it was on the banned substance list (thank goodness that changed).  Interestingly, most studies on caffeine have been done on men, not women.  This study looked at the effects caffeine would have on strength and power of the knee flexors and extensors.  

Ten female soccer players were assigned to either a placebo or caffeine group.  The caffeine (or placebo) was ingested 60 minutes prior to starting activity.  They firs ran 6 15 minute treadmill intervals, with 2 minutes of each block corresponding to specific percentages of VO2max.  Each participate then performed 5 concentric contractions, eccentric contractions and isometric contractions of the knee flexors and extensors.  The caffeine group had significantly higher values for the knee flexor eccentric contractions but not for the knee extensors and there was no difference with concentric contractions.  

So what does a knee flexor eccentric contraction do for you? During the stance phase of running, and into the push off phase, your need eccentric control of knee flexion to keep your leg stable.  If there is weakness, you can compensate with rotation or hip drop.  So an extra cup of coffee may not be a bad idea if you are looking to improve your running gait!


Ali, A., O’Donnell, J., Foskett, A., Rutherfurd-Markwick, K.  The influence of caffeine ingestion on strength and power performance in female team-sport players.  Journal of International Society of Sports Nutrition.  2016. 13:46. DOI 10.1186/s12970-0157-4. 

Leah Peterson