Assessment of Maximum Inspiratory Pressure. Prior Submaximal Respiratory Muscle Activity ('warm-up') Enhances Maximum Inspiratory Activity and Attenuates the Learning Effect of Repeated Measurement

Background: The variability of maximal inspiratory pressure (PImax) in response to repeated measurement affects its reliability; published studies have used between three and twenty PImax measurements on a single occasion.

Objective: This study investigated the influence of a specific respiratory 'warm-up' upon the repeated measurement of inspiratory muscle strength and attempts to establish a procedure by which PImax can be assessed with maximum reliability using the smallest number of manoeuvres.

Methods: Fourteen healthy subjects, familiar with the Mueller manoeuvre, were studied. The influence of repeated testing on a single occasion was assessed using an 18-measurement protocol. Using a randomised cross-over design, subjects performed the protocol, preceded by a specific respiratory warm-up (RWU) and on another occasion, without any preliminary activity (control). Comparisons were made amongst 'baseline' (best of the first 3 measurements), 'short' series (best of 7th to 9th measurement) and 'long' series (best of the last 3 measurements).

Results: Under control conditions, the mean increase ('baseline' vs. 'long' series) was 11.4 (5.8)%; following the RWU, the increase (post RWU 'baseline' vs. 'long' series) was 3.2 (10.0)%. There were statistically significant differences between measurements made at all 3 protocol stages ('baseline', 'short' and 'long' series) under control conditions, but none following the RWU.

Conclusions: The present data suggest that a specific RWU may attenuate the 'learning effect' during repeated PImax measurements, which is one of the main contributors of the test variability. The use of a RWU may provide a means of obtaining reliable values of PImax following just 3 measurements.