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Reliability of the First Ventilatory Threshold Assessment in People With Neuromuscular Diseases: Impact on Exercise
Tim Veneman1, Eric Lukas Voorn1, Jacco Engel1
1Amsterdam UMC location University of Amsterdam, Rehabilitation Medicine, Amsterdam; Amsterdam Movement Sciences, Rehabilitation & Development, Amsterdam, The Netherlands.
Objective:
To determine the interrater and test-retest reliability of the first ventilatory threshold (VT1) assessment in people with neuromuscular diseases (NMD) and its impact on exercise prescription and evaluation.
Design:
Reliability study.
Setting:
Academic hospital.
Participants:
Fifty-one ambulatory adults (mean ± SD age: 63.2±10.3) with Charcot-Marie-Tooth disease (n=20), chronic idiopathic axonal polyneuropathy (n=12), postpolio syndrome (n=11), muscular dystrophy (n=6), or other NMD (n=2).
Interventions:
Not applicable.
Main Outcome Measures:
Oxygen uptake, heart rate, and workload at VT1 were assessed independently by 2 raters from 2 submaximal incremental exercise tests on a cycle ergometer, 1 week apart. VT1 was determined using the V-slope and ventilatory equivalents methods. Reliability was determined using intraclass correlation coefficients (ICCs) and a paired t test for systematic differences. Measurement error was expressed as the standard error of the mean (SEM) or coefficient of variation (CV), and limits of agreement (LoA).
Results:
ICCs were good to excellent for interrater reliability (95% confidence interval, 0.80-0.98), and moderate to excellent for test-retest reliability (95% confidence interval, 0.73-0.95). Interrater and test-retest SEM and CV ranged between 4.9% and 12.6%, with limits of agreement ranging from 14% to 31%.
Conclusions:
ICCs indicated moderate to excellent reliability of VT1 assessments. Measurement errors were low at the group level, with small SEM values, but higher at the individual level, with wide LoA. Considering these results, VT1 can be used to detect changes in aerobic capacity in NMD at the group level, but not at the individual level. If VT1 is used to guide personalized exercise prescription, clinicians should anticipate that target intensity zones may be over- or underestimated in some cases, requiring close monitoring.
