Journal Title (Medline/Pubmed accepted abbreviation): Med. & Sci. Sports & Exerc.
Page numbers: 1538-1543
Summary of background and research design:
Background: Osteoarthritis (OA) is a disease associated with pain and stiffness in joints. An association has been noted between increased quadriceps strength and improved knee function. Since exercise is very painful with OA, there is interest in potential ways to increase quadriceps strength with minimal exercise. Creatine increases muscle mass and strength by increasing energy provision.
Hypothesis: Creatine will enhance the effects of a resistance exercise routine on knee function in patients with OA.
Subjects: Twenty-four women, age about 53-61yrs old
Experimental design: randomized, double-blind, parallel-group, placebo-controlled
Treatments: Creatine monohydrate: 20 g/day divided into 4 doses per day for 7 days and then single 5 g doses per day for 11 wks, or a placebo: dextrose.
Protocol: The participants were randomized to take one of the two treatments for 12 wks. In addition to supplementation, they participated in a resistance training program during the same 12 wks. Before and after 12 wk supplementation, the participants completed exercise tests assessing physical function of their knees and amount of muscle mass and strength. The physical performance test before and after supplementation/exercise involved the time-stand test which assesses the number of times a person can stand (and then sit) from a 45 cm armless chair in 30 sec. To evaluate strength, participants determined their 1 repetition maximum on the leg press. They also completed questionnaires regarding joint stiffness, pain, and quality of life.
The exercise program involved leg press, leg extension, and half-squat exercises, completing 4 sets of 8-12 repetitions of a given percentage of their 1 repetition maximum. Weight was increased as strength increased.
Summary of research findings:
- About 50% of the participants correctly identified their supplement. Since this is the proportion that would be expected from random guessing, the supplements were likely indistinguishable.
- Adherence to the exercise program was about 70-85% and was not different between groups.
- Those in the creatine group significantly increased performance on the time-stand test but the placebo group did not (creatine: 15.7 ± 1.4 for pre-intervention and 18.1 ± 1.8 for post; placebo: 15.0 ± 1.8 for pre and 15.2 ± 1.2 for post).
- Muscle strength on the leg press increased for both groups similarly with intervention.
- Both groups reported less pain. On average, only the creatine group reported less stiffness and improved quality of life.
- Total lean body mass increased similarly in both groups. Lower leg mass increased to a greater extent in the creatine group.
- No adverse effects were reported; creatinine clearance was similar for both groups indicating no deterioration in kidney function.
Key practice applications:
With a resistance training program, creatine can help alleviate the debilitating effects of OA to a greater extent than the resistance training program alone. This is important because it is common for those with OA to have reduced lower limb muscle size and strength, which can exacerbate their condition. Creatine might be recommended for those with OA, especially since no adverse effects were reported, and many could not distinguish between creatine and dextrose (sugar). It would have been interesting, also, to see if creatine supplementation might have had an effect on muscle function without the resistance training program.
In Table 3, the pre-supplementation scores for the Lequesne and WOMAC pain, stiffness, and physical function scales appear to be somewhat higher for the placebo vs. creatine group. Given these differences, which might have been significant in some cases, the ANCOVA statistical approach, with the pre-supplementation value as the covariate, might have been a better method. There are some potentially questionable findings of statistical significance in the table. For example, the pre-post difference in the Lequesne scale for the creatine group was 1.6 units and was reported to be statistically significant. However, the pre-post difference in the placebo group was 2.1 units and was not significant. In both groups, the variability was similar. A potential explanation is the slightly smaller sample size in the placebo (n=11) versus creatine (n=13) group, but these data are still somewhat equivocal. In fact, for the WOMAC pain scale, both the creatine and placebo groups improved significantly (P = 0.012 and 0.049, respectively). The same was true for the PVNS values. Thus, these data are not overwhelmingly supportive of a positive effect of creatine on quality of life and pain ratings in knee osteoarthritis.