The 2- and 6-Minute Walk Tests in Neuromuscular Diseases: Effect of Heart Rate Correction on the Learning Effect

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.

Aerobic anti‐gravity exercise in patients with Charcot–Marie–Tooth disease types 1A and X: A pilot study

“…Thus, at least some of the increased walking distance at posttest is explained by a learning effect with greater physical effort at retest. A learning effect for 6MWT has previously been documented for NMDs (Knak, Andersen, Witting, & Vissing, 2017;Prahm, Witting, & Vissing, 2014). Caution should be exercised when applying HR as an indicator of physical effort in training studies, as HR is influenced by fitness, but this is primarily of relevance if HR is reduced after the aerobic intervention, which was not the case in the present patient.…”

Moderate‐intensity aerobic exercise improves physical fitness in bethlem myopathy

“…In the training group, when correcting for heart rate to abolish the learning effect, no significant change in the 6MWT occurred (3.7 ± 0.4 to 4.2 ± 0.4 meters/bpm; P = 0.054). However, distance walked compared with the predicted distance was corrected for gender, height, weight, age and exertion in the 6MWT, changes were significant (73 ± 15 to 79 ± 15% of predicted walking distance; P = 0.004).…”

“…Patients participated in a 6‐min walk test (6MWT), 5‐times‐sit‐to‐stand‐test (5TSTST), and a 14‐step stair‐test (14SST) as previously described …”

Prospective Natural History Study in 24 Adult Patients With LGMDR12 Over 2 Years of Follow-up

“…This is possibly due to a learning effect, as has been previously described for the 6MWD in both the healthy controls and patients with neuromuscular disorders. 32 The fact that only patients with early-stage fat replacement also experienced a significant decrease in the 10MWT, but not more severely affected patients, presents a further argument for this hypothesis.…”