Reliability and Physiological Analysis of an Isometric Test of Localized Muscular Fatigue

Introduction: The isokinetic dynamometer, considered a gold standard tool for physical evaluation, is widely used in studies that aim to evaluate the reliability and reproducibility of localized muscular endurance (LME) tests. However, such tests may not represent full LME by fixing time or number of replicates. Therefore, it is relevant to construct a test that respects the actual capacity of each subject to withstand fatigue and to submit such a test to validation, as well as to physiological analysis.

Research objectives: To assess the inter- and intra-rater reliability of a localized isometric endurance test (IET) on the isokinetic dynamometer and to establish the metabolic demand required during the test.

Design: Reliability study with test-reteste dynamic.

Participants and Setting: After fulfilling the eligibility criteria, eighty-eight male participants will participate in the study. The inclusion criteria include: healthy male, aged between 18-30 years who agree to participate in the study. Participants with the following will be excluded from the study: presence of anemia, inflammation, being sick, training or physical activity at least 24 hours prior the application of the test, being influenced in some way by test information, do not understand the teste and occurrence of musculoskeletal injury during the study.

Procedure: In phase 1 forty-eight participants will submitted to reliability of the IET within three sessions: familiarization session, test session and retest sessio. In phase 2 forty participants will be submitted the metabolic demand required during the IET will be analyzed by means of gas analysis, blood lactat concetrate and muscular activation percentage.

Intervention: This is a test that was developed by the Laboratory of Sports Physiotherapy of FCT/UNESP - Presidente Prudente. The test will be performed on the Biodex System Pro 4 isokinetic dynamometer (Biodex Medical System, Shirley-NY, USA). At first, participants will be be positioned and fixed on the device itself by their trunk, hips, thighs and by the distal region of the assessed lower limb (dominant). The protocol is composed by a 10 knee flexo-extension warm up at the speed of 330º/s, respecting the amplitude of 90º, then a 30 second isometric contraction from 50% to 60% of the maximum participant effort, according to the Effort Perception Scale. The test starts after two minutes of rest. So that it can take place, participants will be instructed to make as much effort as possible, according to the same scale, for as long as possible, until they can't keep muscle contraction no longer. To stimulate participants, evaluators will offer verbal motivation and they will follow a monitor, coupled to the device, which offers the power generation line which works as a visual feedback during all test long.

In phase 1, the first of familiarization is to the participants understand the test and familiarize with the equipment after 24 to 48 hours, the participants will do the test applied twice at the same day with 10 minutes of rest. For realization of the IET the participants will be instructe to make the maximum effort as possible and mantain until they can't resiste. After one week the retest session will be doing. The order between the evaluators will be changed in the test and retest sessions. In phase 2, the participants will be submitted two sessions, familiarization session and test session. In the test session there is be two teste applied in the same day with approximately 20 minutes of rest. In the first test, thers is gas analysis during all the test until seven minutes after the test and blood lactat concentrate will be colected before the test with 10 minutes of rest, immediately after the teste and in the first, in the third, fifth and seventh minutes after the test. In the second test will be assess the muscular activation porcentage of lateral vastus muscle by means of twitch interpolation technique there is be performe before and after the test.

Measurements: The measurements include time of execution of test (in seconds), work of test (in N.m), physiological (gas analysis, blood lactate concentration, muscular activation percentage) and psychological outcomes (Psychological Questionnaire, Work Ability Index Questionnaire, Perceived Stress Scale, The Bergen Insomnia Scale, Need for Recovery Scale, The Borg Scale, The Borg CR10 Scale, The Effort Perception Scale and Recovery Perception Scale) and clinical outcomes (heart rate).

Analysis: To analyse the normality will be used Shapiro Wilk test. For analysis of reliability test-retest will be used the intraclasse correlation coefficient (ICC), with confidence interval of 95% to reliability relative. To assess the reliability absolute the typical error and coefficient of variation will be done. The paired test t will be do to verify diferences n the mean of the groups. The psychological outcomes wiil be done with correlation and linear regression as well the physiologica outcomes. A significance level of 5% will be assumed for all statistical analysis.