CREATINE RESPONDERS VS. NONRESPONDERS

[Gregor]

Schoch et al. JISSN 3(1):60-66, 2006--06/23/2006

Abstract

Schoch, R.D., D. Willoughby, M. Greenwood. The regulation and expression of the creatine transporter: a brief review of creatine supplementation in humans and animals. Journal of the International Society of Sports Nutrition. 3(1): 60-65, 2006.

RESPONDERS VS. NONRESPONDERS

Most studies have reported an increase in

intramuscular creatine levels with

supplementation; however, variability does

exist. This poses the possible scenario of

“responders†versus “nonresponders†to creatine

supplementation. It is hypothesized that much

of this variability lies within the regulation and

activity of the creatine transporter.

Unfortunately, most of the limited creatine

supplementation research conducted

investigating the expression of CreaT has been

through animal models, as previously noted.

Greenhaff et al observed that approximately 20-30%

of participants following a creatine loading

regime did not respond with an increase in

intracellular creatine 24 . This was defined as

resting total muscle creatine levels less than

10mmol/kg following a 5 day creatine loading

phase at 20g/d. Responders were then classified

as achieving a 20mmol/kg increase following

the loading phase. Recently, Syrotuik and Bell 25 conducted a descriptive profile of individuals

portraying Greenhaff’s classification of

“responder†and “non-responderâ€Â

characteristics. Results of this study concluded

that the responders generally:

1) possessed a

lower initial quantity of intramuscular creatine

and were able to absorb and take up a greater

amount through supplementation; 2) had a

greater percentage of type II fibers; 3) had a

greater fiber cross sectional area; and 4)

possessed more fat-free mass. This data

suggests that an individual’s biological profile

may partially determine the efficacy of a

creatine supplementation protocol.