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Laurance Johnston, Ph.D.

If you wander through health-food stores, you may see muscular bodybuilders checking out creatine supplements. Many athletes now consume them to build strength and enhance athletic performance, especially for physical efforts requiring energy bursts. Since English Olympians initially brought attention to creatine’s performance-enhancing benefits at the 1992 Barcelona games, creatine’s popularity has skyrocketed.  Its effectiveness is now supported by numerous scientific studies, including those suggesting benefits for people with physical disabilities, including spinal cord injury (SCI). Furthermore, animal studies indicate that creatine supplementation exerts a neuroprotective effect after SCI and traumatic brain injury (TBI) and with amyotrophic lateral sclerosis (i.e., Lou Gerhig’s Disease).

Our bodies contain more than 100 grams (28 grams = 1 ounce) of creatine, mostly in our muscles, heart, brain, and testes. Physical activity stimulates primarily the liver to produce about two grams of creatine daily from three key amino acids: glycine, arginine, and methionine. The creatine is then sent through the blood and transported into muscle cells. 

Creatine can also be provided by diet, especially one rich in meat and fish. Vegetarian diets, however, often lack not only creatine, but also the methionine precursor needed for internal production. For comparison’s sake, a pound of meat contains about 40-times more creatine (two grams) than a pound of milk.

Creatine-Generated Energy:

Most muscle creatine is converted into the energetically powerful creatine-phosphate. The high-energy molecular bond connecting the creatine to the phosphate group is an energy source that can quickly fuel muscle activity. This fueling, however, is mediated through the creation of yet another powerhouse molecule called adenosine triphosphate (ATP).

ATP is extremely important because it is the body’s energy currency, expended to drive most biochemical processes. Like creatine-phosphate, ATP’s terminal phosphate group is connected by a high-energy bond that when severed provides energy needed for muscle contraction.

Under more constant or endurance working conditions, the body obtains ATP by metabolizing carbohydrates and fats, a relatively slow process that cannot generate immediately needed ATP energy.

When energy bursts are required, the body uses instead creatine-phosphate. Specifically, the phosphate group on this molecule is transferred to replenish spent ATP, transforming it into its energetically powerful form.  During rest periods, creatine-phosphate is then replenished by the ATP generated by the slower metabolic processes.

Phosphocreatine + Adenosine-diphosphate ---> Creatine + ATP

If intracellular creatine-phosphate levels can be increased, for example, through supplementation, it will take longer before the short-term energy source is depleted and a switchover to slower carbohydrate or fat metabolism is needed. 

This process can be visualized as if you have a large wad of cash (i.e. creatine-phosphate) in your wallet. It’s there, ready to be used to meet your immediate needs. The more you supplement this wad, the more energy purchases you can quickly make.  In contrast, generating your energy through carbohydrate or fat metabolism is the equivalent of writing a check that must clear the system, a more time-consuming process better suited to meet your long-term, larger needs.

Strength & Muscles:

Creatine supplementation is most useful for physical activities that require intense bursts of energy - e.g., a bench press, a sprint, or games requiring energy bursts. It is less useful for endurance events, except when such events are enhanced by building-up muscle strength through creatine-stimulated weightlifting.

Creatine can build muscle mass by several mechanisms. For example, because weightlifting is exactly the sort of short-term, intense physical activity fostered by creatine, more repetitions and harder workouts can be achieved, building up muscle. In addition, however, creatine increases water uptake into the muscle, a process called cell volumizing that bulks up the muscles in a fashion that may not add much real strength.

Supplementation Cycle:

In one commonly used, creatine-supplementation cycle, four 5-gram doses of creatine are consumed daily for five days. These are often dissolved in a sweetened solution to enhance uptake. After this loading phase, the daily dose is reduced to two grams for a month, after which supplementation is discontinued for an additional month. The cycle then starts over.

The washout period is recommended because increased creatine levels will eventually trigger the body to shut down its creatine production and transport into muscle from the blood. After the washout period, the body regains these functions. Although some physical gains may be lost, because more intense workouts were achieved during the earlier supplementation phase, the next cycle will start at a higher baseline.

Side Effects:

In addition to potential transient gastrointestinal disturbances, chronic creatine supplementation may stress kidneys and increase exposure to potential, manufacturing-process contaminants. Although risk appears low given its extensive history of use, normal metabolic patterns are affected to obtain the desired benefits, which over time may have yet undefined deleterious effects.

Physical Disability:

Studies suggest that creatine can enhance strength compromised by physical disability.

First, investigators at the Miami Project have shown that creatine promotes upper-extremity work capacity in quadriplegics (Jacobs, et al, Arch Phys Med Rehabil, 83, January 2002, pp. 18-23).

In this study, 16 male quadriplegics with complete cervical C5-7 injuries were randomly assigned to receive either 20 grams/day of creatine or placebo maltodextrin (a common food ingredient) for seven days. Treatment was then discontinued for a three-week washout period, after which the treatment groups were reversed for another seven days - i.e., the initial placebo group now received creatine, and the initial creatine group now was given maltodextrin.

Work capacity was assessed before and after each dosing period using arm ergometry, a common SCI-rehabilitation exercise. Specifically, subjects faced a series of two-minute, increasing-intensity work stages with one-minute, intervening recovery periods.

After creatine supplementation, improvements were noted in various respiratory measurements, including oxygen uptake, carbon dioxide production, tidal volume (amount of air that enters the lungs), and breathing rate. For example, 14 of the 16 subjects demonstrated increased oxygen uptake, averaging an impressive 18.6 %. Improvements were also noted in peak power output and increased time to fatigue.

Second, Dr. Kenneth Adams and colleagues, University of Texas, Southwestern Medical Study Center, Dallas carried out a creatine-loading study in 10 subjects with SCI. The subjects had their peak-power production tested on an upper extremity exercise machine before and after creatine supplementation. Eighty-eight percent improved their peak-power production, with quadriplegics and paraplegics averaging 21and 13% improvement, respectively (Adams, et al, Arch Phys Med Rehabil, 81, September 2000, p. 1263).

Third, Drs. Stephen Burns and Richard Kendall, University of Washington have also evaluated the effects of creatine supplementation on arm strength in C-6 quadriplegics (personal communication). In this study, however, preliminary analyses indicated no major benefits. Burns speculates that creatine supplementation provides to both SCI and neurologically intact individuals similar modest benefits in response to repeated maximal efforts on short-duration exercises. However, these benefits may be offset by weight gains attributed to non-strength-associated water uptake. In other words, you may be hauling around more weight that will enhance neither sporting nor transfer ability.

Finally, investigators have shown that creatine can increase handgrip, knee-extension, and ankle strength in individuals with various forms of neuromuscular disease (Tarnopolsky, M. & Martin, J., Neurology, 52, 1999, pp 854-7).

The differences in the indicated benefits between studies are not surprising because results can be affected by many interacting factors, including, in these cases, the selected outcome measures, dosing regimens, and sample sizes (e.g., more subjects may statistically demonstrate subtler effects).

Neuroprotective Effect?

Animal studies indicate that creatine exerts a neuroprotective effect in SCI and TBI. For example, Sullivan et al. (U. Kentucky) demonstrated that creatine supplementation ameliorated the extent of experimentally induced brain injury 36% in mice and 50% in rats (Ann Neurol,48(5), 2000, pp 723-729). Hausmann et al. (2002, U. Zurich) demonstrated that 4-weeks of creatine supplementation before experimental spinal cord injury reduced glial scar formation and enhanced functional recovery in rats (Spinal Cord, 40(9), 2002, pp 449-456). Finally, Rabchevsky and colleagues (2003, U. Kentucky) showed that creatine supplementation spared spinal cord gray matter in injured rats (gray matter contains neuronal cell bodies and dendrites and glial cells; white matter consists mainly of axons). The investigators felt that the neuroprotective effects were less for SCI than TBI because the latter affects gray matter to a much greater degree (J Neurotrauma., 20(7), 2003, pp 659-669)

These studies suggest that dietary supplementation with creatine may be a promising approach for reducing neurological damage after TBI or SCI.

Concerning ALS, in a mouse model of the disorder, Klivenyi et al (Harvard U.) showed that creatine supplementation protected mice from neuronal loss and suggested that such supplementation may be a new therapeutic strategy for ALS (Nat med, 5(3), 1999, pp 347-350).


In conclusion, although more definitive studies are needed, creatine’s potential benefits have important ramifications for many with physical disabilities because the enhancement of residual strength, even to a limited degree, often can have profound quality-of-life implications. Furthermore, creatine supplementation may exert neuroprotective effects after TBI and SCI and also with ALS.

Resources: An excellent review of creatine studies has been posted on (click on CareCure Community and scroll down to the creatine article).

Adapted from article appearing in Paraplegia News, November 2002.

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