Abstract
Objective: The 2- and 6-minute walk tests are common measures for evaluating walking ability, but reliability is weakened by a well-documented learning effect. Since heart rate is related to workload, any change in walking distance, which is unrelated to change in clinical function, should be reflected in a change in heart rate during walking. Therefore, the aim of the present study was to investigate test-retest reliability of the 2- and 6-minute walk tests with and without heart rate correction. Methods: Ninety-three adult patients (mean age of 53 years, range; 22-83 years) with 12 different neuromuscular diseases (myotonic dystrophy type 1, limb-girdle muscular dystrophy, facioscapulohumeral muscular dystrophy type 1, Charcot-Marie-Tooth disease, mitochondrial myopathy, Becker muscular dystrophy, spinobulbar muscular atrophy, sporadic inclusion body myositis, spinal muscular atrophy, myotonia congenita Thomsen disease, congenital myopathy, polymyositis) were recruited in the study. One 2- and 6-minute walk test was performed on two occasions, 1-2 weeks apart. Heart rate was monitored by a pulse-watch. Results: The distance walked increased significantly with repeated 2- and 6-minute walk tests (2-minute walk test increased by 4 ± 9 m and 6-minute walk test by 11 ± 26 m, p<0.001). Heart rate correction eliminated the learning effect in the 6-minute walk test (+0.01 m/heartbeat, p=0.84), but not in the 2-minute walk test (+0.03 m/ heartbeat, p=0.018). The same pattern of heart rate-correction in the 6-minute walk test was observed in all subgroup diagnoses. There was no difference in the learning effect between disease severities. Conclusion: Both the 2- and 6-minute walk tests are associated with a learning effect. The learning effect is eliminated when correcting for heart rate in the 6-minute walk test, but not in the 2-minute walk test. The results suggest using a heart rate corrected 6-minute walk test to weed out day-to-day variations that are not due to a real change in the patient’s clinical condition.
Highlights
The 2-minute walk test (2MWT) and 6-minute walk test (6MWT) are submaximal exercise tests that are easy to administer and require no expensive equipment [1]
The total walked distance in the 2- and 6MWTs correlated with average heart rate (HR) during the walk tests (r=0.47 and r=0.49 respectively, p
The same pattern of HR-correction in the 6MWT was observed in all subgroup diagnoses
Summary
The 2-minute walk test (2MWT) and 6-minute walk test (6MWT) are submaximal exercise tests that are easy to administer and require no expensive equipment [1]. Both tests are used in the clinic and in clinical trials for evaluating walking ability in patients with neuromuscular diseases (NMDs). A pilot study in 16 patients with neuromuscular diseases indicated that the variability of the 6MWT can be eliminated by correcting for heart rate (HR) during the test [2]. The rationale for eliminating variation in walking distance in the walk tests that is not due to a real change in the patient’s clinical condition, by HR-
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