Biochemical changes in relation to a maximal exercise test in patients with fibromyalgia (FM)

Patients with fibromyalgia often complain of fatigue and pain during

exercise and of worsening of pain days after exercise. The aim

of the study described here was to determine if abnormal

changes in potassium or lactate could be observed during an

exercise test in fibromyalgia. Whether an abnormal incline in

plasma creatine kinase or myoglobin could be observed days

after the test was studied also.

Fifteen female fibromyalgia

patients and 15 age- and sex-matched controls performed a

stepwise incremental maximal bicycle-ergometer test. Blood

samples were collected from a catheter in a cubital vein. The

changes in heart rate, potassium levels, and haematocrit

during the exercise test were similar in the two groups. The

maximal obtained lactate concentration was 4.2 mmol l-1

(3.5-5.6) in the patients as compared to 4.9 mmol l-1

(3.9-5.9) in the controls (NS). The estimated anaerobic

threshold of 2 mmol l-1 was reached at a heart rate of 124

min-1 in the patients with fibromyalgia as compared to 140

min-1 in the controls (P = 0.02). In relation to workload, the

patients scored higher on a Borg scale for perceived exertion

during exercise, but if the Borg score was related to lactate

no significant difference was found.

The patients reported 86%

and 79% of maximal pain in the thighs on the visual analogue

scale 1 and 2 days after the test, but the creatine kinase and

myoglobin concentrations were not increased.

Norregaard J, Bulow PM, Mehlsen J, Danneskiold-Samsoe B

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