Biomedical Sciences and Engineering MS Thesis Defense by Beatrice Selen Şenocak

KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

BIOMEDICAL SCIENCES AND ENGINEERING

MS THESIS DEFENSE BY BEATRİCE SELEN ŞENOCAK

Title: Standardization of maximal voluntary isometric contraction (MVIC) measurements from the elbow flexors

Speaker: Beatrice Selen Şenocak

Time: June 4, 2018, 10:00

Place: SOS 277

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Prof. Dr. Kemal Türker (Advisor, Koç University)

Prof. Dr. İsmail Lazoğlu (Koç University)

Doç. Dr. Barış İşak (Marmara University)

Abstract:

Despite the routine measurement of maximal voluntary isometric contraction (MVIC) in research and in the clinic, no reference protocol for collecting MVIC measurements exists in the literature, specifically, with regards to the number of MVIC attempts to be performed and the duration of the rest period between contractions. The aim of this study was to develop a non-fatiguing MVIC protocol for the elbow flexors of healthy subjects. A total of 51 subjects, ages 18-34, participated in the study. Subjects were randomly assigned to complete 1 of 4 MVIC protocols with different rest periods (i.e. 10, 15, 30, and 60 seconds) between each maximal contraction. Maximum force applied to a force sensor, surface EMG of the biceps brachii muscle, subjective pain and subjective fatigue self-report scores were recorded for each attempt. Nonparametric statistical tests were used to determine differences between attempts but were inconclusive. As the development of fatigue is gradual, cumulative sum (CUSUM) charts were also constructed to explore subtle but persistent shifts in the data from the average of the first 10 attempts. An error box method, similar to what has previously been employed to detect reflex onset from electromyography records was used to determine whether continuous positive or negative deflections in the CUSUM charts were significant. CUSUM charts of the force data revealed significant negative deflections in force in the 60s, 15s and 10s groups, and in median frequency in the 15s and 10s groups. Significant positive deflections in the CUSUM charts of pain and fatigue self-report data were evident in all groups. For both pain and fatigue self-report scores, the deflections with the earliest onset were seen in the 10s group. It was concluded that the protocol with 15s of rest resulted in peripheral fatigue starting after attempt 5, but no central fatigue even after 25 successive attempts. The protocol with 15s of rest seems to have been conducive in maintaining the subject’s attention to the task and motivation to do well. We therefore suggest an MVIC protocol consisting of 5 attempts, with a rest period of 15s between each attempt. We also suggest that the research team provides live encouragement during the contractions and averages the force values from the 5 attempts, given normal fluctuations in human performance. Finally, we propose a method for detecting fatigue from maximal force, median frequency and subjective fatigue data using CUSUM charts with error boxes.