AbstractsMedical & Health Science

Reliability of Measuring Voluntary Quadriceps Activation Using the Burst Superimposition and Interpolated Twitch Techniques

by Kimberly N Frissora

Institution: University of Toledo
Department: Exercise Science
Degree: MS
Year: 2014
Keywords: Health Sciences; Sports Medicine
Record ID: 2025804
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396516819


Objective: To determine the reliability of quantifying quadriceps percent activation of both the burst superimposition stimulation technique (SIB) and interpolation twitch technique (ITT) of stimulation. Additionally, this investigation will identify the reliability of using train and doublet stimuli during both stimulation techniques. Assessment of reliability was conducted over two separate testing sessions spaced one week apart. Design and Setting: Intraclass Correlation Coefficients (ICCs) were created to assess the reliability of SIB train, SIB doublet, ITT train, and ITT doublet conditions. All data were collected in a research laboratory. Subjects: Sixteen healthy subjects (9 female, 6 male,) participated in this study. Measurements: A Digitimer DS7AH constant current stimulator with a 200 µs max pulse duration (Digitimer Ltd., Hertfordshire, England) and Digitimer DG2A train/delay generator (Digitimer Ltd.), was used for muscle stimulation. Torque data were quantified using a custom-written computer software program (Microsoft Visual Basic, Redmond, WA). Subject-specific maximal current intensities were used during testing. Maximal current was determined by stimulating the quadriceps muscle (SIB) or femoral nerve (ITT) with an individualized intensity not exceeding 400 V and a pulse duration/width of 1000 µs. Individualized intensity was determined at rest, with single pulses of increasing intensity until the torque associated with the electrically evoked muscle contractions reached a plateau and then decreased. During testing conditions (both ITT and SIB) the current that produced the greatest knee extensor torque at rest, plus an additional 20% (typical range of 100 to 400 mA), was given during a maximal quadriceps contraction. An additional 20% was added to that intensity to ensure a supramaximal stimulus during testing. Results: The SIB train showed a poor reliability (ICC = 0.087) while the SIB doublet showed less consistency, with a poor reliability (ICC = 0.349). For the ITT, the train condition also displayed fair reliability (ICC = 0.071) while the ITT doublet had the most dependability, with a strong reliability over the course of the two testing sessions (ICC = 0.312). Conclusions: Ideally, a strong reliability is demonstrated by ICC values of 0.8-1.0. This study determined that none of the techniques or conditions were reliable over the course of the two testing sessions. However, further research must be done in order to determine further reliability of these studies.