Synthesized by the liver, kidney and pancreas, creatine occurs naturally and is found primarily in skeletal muscle. It can be obtained from eating foods rich in creatine such as meat and fish or be consumed in the form of supplement powders. The most predominant form of creatine is phosphocreatine which contributes to the rapid re-synthesis of adenosine triphosphate (ATP) during short-term, high-intensity exercise. Dietary supplementation of creatine has been shown to improve strength, power and recovery from high-intensity exercise in the non-SCI population (Balsom et al. 1995; Casey et al. 1996; Earnest et al. 1995; Harris et al. 1993). Creatine serves as a short duration reservoir for the energy required for muscle contraction in skeletal muscle. Low levels of intramuscular creatine are seen in some neuromuscular diseases. Creatine supplementation improves muscle strength in some patient populations with neurological disorders (Kendall et al. 2005).
|Kendall et al. 2005
Population: Level of injury: C5/C6; Severity of injury: AISA A-C; Time since injury=16.5 yr.
Intervention: Subjects were randomized into one of two groups receiving either 10 g creatine orally twice daily for six days, then maintained on 5 g daily until testing, or placebo. After a wash-out period they crossed over to the other arm.
Outcome Measures: Grasp and Release Test (GRT) and Functional Independence Measure.
|1. There were no significant between-group differences for GRT or FIM scores.|
|Jacobs et al. 2002
Population: Mean age=35.3 yr; Gender: males=16 females=0; Level of injury: tetraplegia; Mean weight=71.4 kg.
Intervention: Individuals received 20 g of creatine monohydrate 4x/day mixed with 8 oz water or placebo powder for 1 wk. A washout period occurred for 3 wk and then individuals crossed over to receive the alternate treatment protocol.
Outcome Measures: Power output, time to fatigue, heart rate (HR), oxygen uptake (VO2), minute ventilation (VE), ventilatory frequency (VF), respiratory exchange ratio (RER), tidal volume (VT).
1. No adverse effects were reported.
2. There was no change in HR, RER and VE, although there were significant difference in VO2, VCO2, VF and VT between trials (p<0.001).
3. VO2 increased by 18.6% with creatine treatment versus placebo.
4. After creatine consumption, VO2, VCO2 and VT reached their highest peak.
|Effect Sizes: Forest plot of standardized mean differences (SMD ± 95%C.I.) as calculated from pre- and post-intervention data.
Kendall et al. (2005) reported findings of a study that sought to determine whether creatine supplementation improves muscle strength, endurance and function in weak upper limb muscles in person with tetraplegia. Eight individuals with tetraplegia and mild wrist extensor weakness were randomized to receive creatine or a placebo in a double-blind crossover design. During creatine supplementation, participants received oral doses of creatine monohydrate powder. There was no change in any of the functional tests performed by the participants and none of the participants had a change in self-reported motor Functional Independence Measure scores.
Persons with SCI have decreased upper extremity work capacity. Individuals with cervical SCI have limited proficiency in the repeated tasks of daily living that require endurance and strength (Hopman et al. 1992; Jehl et al. 1991; Lin et al. 1993; Van Loan et al. 1987). A study by Jacobs et al. (2002) sought to determine the effects of oral creatine monohydrate supplementation on upper-extremity work capacity in persons with complete cervical SCI. Sixteen men with complete tetraplegia (C5-7) were randomly assigned to one of two groups and received either 20g of creatine monohydrate supplement powder daily or placebo for the first treatment phase; treatment was reversed in the second phase. Each treatment phase lasted for 7 days with a 21-day washout period. Peak power output, time to fatigue, HR, and metabolic measures including oxygen uptake, minute ventilation, tidal volume and respiratory frequency were assessed. Significantly greater values of oxygen uptake, tidal volume and carbon dioxide production were observed in the groups receiving the creatine monohydrate supplementation. The investigators concluded that creatine supplementation enhances exercise capacity in persons with complete tetraplegia and may promote greater exercise training benefits.
There is level 1a evidence (from one RCT: Kendall et al. 2005) that creatine supplementation did not result in improvements in wrist extensor strength or muscle function.
There is level 1a evidence (from one RCT cross-over trial: Jacobs et al. 2002) that creatine supplementation enhances exercise capacity in persons with complete tetraplegia and may promote greater exercise training benefits.