Creatine is one of if not the most popular dietary supplement on the market worldwide.  Athletes from many different sports have been known to supplement creatine because it is one of the few supplements that has not been banned.  There are many different opinions in regards to creatine's effectiveness and if it truly do improve athletic performance. Creatine is used by athletes at many levels, from middle school to professional (table 1).

Table 1:  Creatine use in various populations of athletes (Rawson & Clarckson, 2003)

Population	Creatine Users	Reference
High School Athletes	17%	McGuine et al., 2002
High School Football Players	30% (grades 9-12) 50% (12th grade only)	McGuine et al., 2001
NCAA Athletes	28 - 41%	Greenwood et al., 2000; LaBotz & Smith, 1999
Military/Civilian Health Club Members	29 - 57%	Sheppard et al., 2000
Athletes in Power Sports	45 - 74%	Rosen et al., 1999; Stanton & Abt, 2000

Hundreds of studies have been performed to examine if exercise and sport performance is effected by creatine supplementation.  In laboratory tests involving cycling, creatine supplementation was found to improve performance in tests requiring repeated bouts of high intensity exercise lasting <30 seconds in duration.  During tests involving longer duration's of >90 seconds or more creatine was less effective.  This is no surprise since creatine plays such an important role in the regeneration of ATP which is the fuel used during high intense short duration activities.

Anaerobic Strength and Power

Creatine supplementation appears to improve performance the most in activities that consist of repeated bouts that are high in intensity.  This is due to the increased level of PCr in type II muscle fibers. Creatine supplementation has been shown to provide as an ergogenic aid in activities involving repeated bouts of sprinting, jumping, swimming, and weightlifting just to name a few.  Hundreds of studies show that creatine supplementation improves performance in repeated high intensity activities because it provides improved rephosphorylation during recovery so that creatine stores within the muscle do not become depleted.

A study by Stone et al. (1999) tested two groups of football players (one placebo and one supplementing creatine) during a 5 weeks on conditioning on vertical jump power, force, and rate of force development.  The creatine group demonstrated much greater vertical jump power, force, and rate of force development.

Another study by Aaserud et al. (1998) compared the effects of creatine supplementation on a 8 x 40m sprint interval tasks by male handball players.  The increase of time from the first to the last sprint decreased for the group that had supplemented creatine.

Bosco et al. demonstrated that creatine supplementation resulted in a very noticeable increase in jumping performance during  two 15 second jump tests with a 15 second rest period in between.

Earnest et al. discovered that creatine supplementation increased subject's total lifting volume by 43% when performing a repetition to failure test using 70% of their 1RM bench press.

There have been mixed results in regards to the effect creatine supplementation has for improving single bout high intensity activities.  A number of studies which involved jumping, running, swimming and weightlifting have failed to show improvements from creatine supplementation.  It is believed that creatine improves single bouts of high intense exercise when an individual has been fatigued due to prior activities.  Creatine supplementation allows an athlete to train at higher intensities and recover quicker between multiple bouts and sets during exercise.
 

Lim et al. (2003) Study Results of Muscular Strength & Power Measurements Between Placebo & Creatine Groups

Activity	Placebo (n=18)	Creatine (n=18)
Bench Press 1RM (kg):  Baseline	47.4 + 5.8	47.6 + 5.0
Bench Press 1RM (kg):  Post	50.3 + 5.8*	55.2 + 5.0*+
Vertical Jump (cm):  Baseline	49.4 + 1.6	49.4 + 2.6
Vertical Jump (cm):  Post	50.9 + 1.7*	52.3 + 2.1

* significant improvement, p<0.05
+ significant treatment effect compared with placebo, p<0.05
 

 
 

Research is limited in regards to the effects of creatine supplementation and its effects on improving aerobic endurance.  Literature suggests that creatine supplementation does not provide an ergogenic effect for aerobic endurance.  It appears as performance duration increases the ergogenic potential of creatine decreases (Branch and Williams, 2002).  Lack of results could very well be due to the lack of energy system specificity that creatine has regarding aerobic activities.  It has also been reported that the potential for increasing lean body mass due to creatine supplementation could negatively affected endurance performance.
 

Changes in body mass and composition have consistently been reported in literature.  numerous studies present data that shows significant increases in total body mass related to short term creatine supplementation.  There are three known mechanism that can explain how creatine supplementation causes changes in body mass and composition.
 

• 1.  Creatine causes water retention due to its osmotic activity.  This is supported in research from findings of decreased urinary
•      output during creatine supplementation.
• 2.  During creatine supplementation increase in body mass may be a result of higher training volume during resistance training.
•      Training at higher volume and intensity in the long term will increase lean body mass.
• 3.  An increase in cellular hydration due to water retention caused by creatine promotes increased protein synthesis and decreases
•      net protein breakdown.  However, more research is needed to verify this mechanism.