Intra-rater reliability of electromyographic recordings and subjective evaluation of neck muscle fatigue among helicopter pilots

Thuresson, Marcus<sup>1</sup>; Äng, Björn<sup>1</sup>; Linder, Jan<sup>2</sup>; Harms-Ringdahl, Karin<sup>1,3</sup>

Affiliations

¹Section of Physiotherapy, Neurotec Department, Karolinska Institutet, Stockholm, Sweden

²The Armed Forces Headquarters, Aeromedical Section, Stockholm, Sweden

³Karolinska University Hospital, Stockholm, Sweden

Abstract and keywords

The aim was to evaluate the reliability of a method of measuring neck muscle fatigue among helicopter pilots.

Method: Surface EMG from three areas in the neck region, bilaterally, was recorded among 10 male helicopter pilots while they were performing isometric contractions in flexion and extension for 45 s, sustaining a force representing 75% of maximum strength in a seated position. Perceived fatigue was rated using the Borg CR-10 scale. The test was repeated twice the first day and then two additional times with one-week intervals. Variables analyzed were the slope of the median frequency change, the normalized slope, and the ratings after 15, 30 and 45 s; and also the initial median frequency (IMDF). The intra-class correlation (ICC) and the measurement error (Sw), intra- and inter-day were calculated statistically.

Results: The best reliability for the slope was found for the 45 s intra-day analysis taking all measurements into account (ICC 0.65–0.83). The reliability after 30 s was poorer but still acceptable (ICC 0.52–0.71). For the subjective ratings, the highest reliability was found after 30 s inter-day (ICC 0.86–0.88). IMDF showed generally high reliability for the intra-day analyses (ICC 0.63–0.80).

Conclusion: The method is reliable for use in further research. Since performing a contraction of 75% of maximum was quite strenuous, we recommend that the protocol be shortened to 30 s.

Keywords: Borg scale; EMG; ICC; Measurement error; Repeatability

Links

DOI: 10.1016/j.jelekin.2004.11.001

PubMed: 15763680

WoS: 000229066100011

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Cited By (1)

Year	Entry
2013	Äng BO, Kristoffersson M. Neck muscle activity in fighter pilots wearing night-vision equipment during simulated flight. Aviat Space Environ Med. February 2013;84(2):125-133.