Creatine Supplementation

Since cr is produced primarily in the liver it must

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: r. Since Cr is produced primarily in the liver, it must therefore be released into the blood and then must enter the muscle cell, against a concentration gradient, with the aid of a sodium-dependent transporter, Cr transporter-1.[7,8] Almost all of the Cr in the human body is located in skeletal muscle with approximately 40% of the Cr in the free form (Cr) and 60% in the phosphorylated form (PCr). In general, a 70kg person with an average Cr pool of 120–140g, would lose about 2 g/day as creatinine in the urine. This loss is replaced by both exogenous consumption of about 1 g/day from a normal mixed diet and the other 1g being synthesised endogenously. 2005 Adis Data Information BV. All rights reserved. There seems to be basic agreement in the literature that PCr levels are slightly higher in type II glycolytic muscle fibres when compared with the more aerobic type I muscle fibres and there is little evidence to suggest any sex differences in PCr concentrations.[9,10] There might be a slight decline in PCr concentration with increased age but it is not clear if this is due to a decline in physical function or to aging itself.[11] 1.2 Brief Historical Perspective Cr was initially discovered in the early 1830s by Chevreul and confirmed as a ‘real’ entity in meat by Liebeg in 1847. Liebeg was also the first to theorise that Cr was somehow linked to muscle performance; however, it was not until the early 1900s when the extraction of Cr from meat began to lead to the investigation of Cr as an oral supplement. The Soviet States and the Eastern block countries began to utilise Cr as a potential performance enhancer in the 1970s,[7,12] but the real push towards studying Cr supplementation did not occur until the early 1990s in the US and Great Britain.[12] Today, it is estimated that >2.5 million kilograms of Cr are used each year,[8] with Cr sales increasing to over $US200 million in 1998.[13] In general, the majority of the scientific literature dealing with young, healthy males, agrees that exercise performance that involves short periods of extremely powerful activity (1–2 seconds) can be enhanced by Cr supplementation, especially if the activity is performed in repetitive bouts separated by short rest periods (30 seconds...
View Full Document

This note was uploaded on 01/28/2014 for the course BI 231 taught by Professor Richardmay during the Fall '13 term at Southern Oregon.

Ask a homework question - tutors are online