The aim of the present study was to investigate whether creatine supplementation may have an additive effect on physical performance in COPD patients participating in a pulmonary rehabilitation programme including exercise training. We failed to prove any differences in walking time (ESWT) after the training period between the groups receiving creatine supplementation or placebo. Our data did not show that exercise training and creatine supplementation improved walking time in ESWT in relative to exercise training and placebo.
All patients included in the study were referred from the Primary Health Care in Stockholm and Linköping County and seemed to be representative for a group of patients with moderate to severe COPD. Today the effect of exercise training in patients with COPD is well established and there are several studies including patients with moderate to severe stage of COPD showing benefits of pulmonary rehabilitation (Wijkstra et al 1994
; Donner and Muir 1997
; Tiep 1997
). When we formed our programme we followed the evidence-based guidelines as outlined in “Pulmonary rehabilitation” (ACCP/AACVPR 1997
). There were no difficulties for the patients to accomplish the exercise programme and reach the desired levels of dyspnea. The ESWT test is a submaximal test of physical performance and should therefore reflect a person’s daily physical performance better than a maximal test. The test has also showed sensitivity to changes after exercise training in COPD patients (Revill et al 1999
In the present study, ESWT improved in both groups. However, the improvement was significant only in the creatine group. There was no significant difference when comparing the results of the ESWT between the groups. Hence, we failed to show any benefit of creatine supplementation in combination with exercise training.
In healthy subjects an increase of 25%–30% of total creatine concentration in the muscles was found after oral creatine supplementation, as well as a significant increase in maximal short-lasting muscle work after oral creatine supplementation. The size of the increase in strength power was approximately 4%–6% (Balsom et al 1993
Gordon and colleagues (1995)
found significantly increased skeletal muscular performance in patients with chronic heart failure compared with a placebo group after oral supplementation of creatine during ten days without any exercise training. They concluded that both patients with heart failure and healthy individuals with low levels of creatine in the muscles show better muscle function after oral supplementation.
Studies of skeletal muscle metabolite concentrations in leg muscle of patients with COPD have shown deranged muscle metabolism with decreased concentrations of ATP and creatine phosphate (Jakobsson and Jorfeldt 1995
). A positive effect in physical performance was therefore expected when creatine was supplemented to training.
A recently reported study, also investigating the effect of creatine supplementation on physical performance in patients with COPD, Fuld and colleagues (2005)
, reports an increase in fat-free-mass, upper and lower limb muscle strength and endurance, but no improvement in whole body exercise capacity. In this study the patients had a loading phase of supplements for 14 days, then a maintenance phase during a 10 week training programme.
In contrary to Fuld and colleagues (2005)
our patients started supplementation with creatine/placebo and exercise training at the same time with one week higher intake of creatine and then a maintaining phase during the rest of the training period, ie, seven weeks. The quantity, duration, and intensity of the training sessions seem to be equal to Fuld’s study except for the fact that we did not provide a home training program to the participants during the exercise programme.
The lacking effect in our study may be due to the fact that we used the submaximal performance test and that the sample size in measuring lower limb muscle strength was low. Also, our programme was not formed to train specified muscle groups. Furthermore, we have no data of skeletal muscle metabolic concentration to show that oral creatine supplementation was accompanied by increased concentration of high-energy phosphates in the leg muscles.
The questionnaire for measuring health-related quality of life (SGRQ) was found suitable for the group of COPD-patients included in the present study. That the degree of physical ability affects the quality of life, and that rehabilitation programmes for COPD patients have a positive effect on physical performance and quality of life has been shown by Jones and colleagues (1992)
. In the creatine group, all three dimensions (symptoms, activity and impact) and the total score in SGRQ changed in a positive direction, but did not reach clinical significance (Jones 2002
). In the placebo group there was a surprisingly large improvement in the dimension of symptoms (15 units) and when we analyzed the data we found that two patients had 40 units in difference from baseline compared with a mean of 7 units change for the rest of the group (n = 6). We speculate that these two patients have had an exacerbation close to baseline and recovered during the training programme.
There is to our knowledge only one study published investigating the effects of creatine supplementation in patients with COPD (Fuld et al 2005
). The results in the present study failed to show an effect of oral creatine supplementation in contrast to Fuld and colleagues (2005)
. Further research in this field to find individual modalities of treatment for patients with COPD is needed (Griffiths and Proud 2005
Our conclusion is that because COPD patients are a very heterogeneous group, they could probably respond very differently to oral creatine supplementation and we need larger studies to find whether oral creatine supplementation is of any benefit for patients with COPD or not.