title: Effect of constant, predictable, and unpredictable motor tasks on motor performance and blood markers of stress.
abstract: An unfamiliar or novel physical stimulus induces activation of dopaminergic neurons within the brain and greater activity in areas involved in emotion; considering this, we aimed to establish whether unpredictable prolonged (fatiguing) motor task (vs. constant vs. predictable) evokes greater dopaminergic activity, enhances neuromuscular performance, motor accuracy, and perception of effort, and delays overall central fatigue. Fifteen healthy male volunteers (aged 22 ± 4 years) were required to perform 1 of 3 exercise trials (at least 1 week apart) of 100 intermittent isometric contraction (IIC) tasks involving knee extensions at 60° flexion. Trials were structured differently by simulated contraction intensity. A fatigue task involved 5-s contractions and 20-s rest. Variables measured before, during, and after IIC were electrically induced force, maximal voluntary contraction, central activation ratio, intramuscular temperature, and blood levels of dopamine, cortisol, and prolactin, and intraindividual motor variability and accuracy (constant and absolute error). We found that IIC increased central and peripheral fatigue, force sensation, and Tmu, and decreased absolute and constant error without visual feedback, but did not affect motor variability. There were no significant differences between the three IIC tasks. However, only unpredictable tasks increased dopaminergic activity, which was insufficient to affect central motivation to perform isometric exercise and alter centrally mediated components of fatigue.
authors.affiliation: Department of Applied Biology and Rehabilitation, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Laura
authors.initials: L
authors.lastname: Kyguoliene
authors.affiliation: Department of Applied Biology and Rehabilitation, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.|Sports Science and Innovation Institute, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Albertas
authors.initials: A
authors.lastname: Skurvydas
authors.affiliation: Sports Science and Innovation Institute, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Nerijus
authors.initials: N
authors.lastname: Eimantas
authors.affiliation: Sports Science and Innovation Institute, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Neringa
authors.initials: N
authors.lastname: Baranauskienė
authors.affiliation: Department of Applied Biology and Rehabilitation, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Dalia
authors.initials: D
authors.lastname: Mickeviciene
authors.affiliation: Department of Laboratory Medicines, Medical Academy, Lithuanian University of Health Science, Kaunas, Lithuania.
authors.forename: Daiva
authors.initials: D
authors.lastname: Urboniene
authors.affiliation: Sports Science and Innovation Institute, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania.
authors.forename: Margarita
authors.initials: M
authors.lastname: Cernych
authors.affiliation: Department of Applied Biology and Rehabilitation, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania. marius.brazaitis@lsu.lt.|Sports Science and Innovation Institute, Lithuanian Sports University, Sporto str. 6, 44221, Kaunas, Lithuania. marius.brazaitis@lsu.lt.
authors.forename: Marius
authors.initials: M
authors.lastname: Brazaitis
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D000886:Anthropometry; D004298:Dopamine / Q000097:blood*; D004558:Electric Stimulation; D004576:Electromyography; D004797:Enzyme-Linked Immunosorbent Assay; D005221:Fatigue / Q000097:blood* / Q000503:physiopathology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology; D010807:Physical Endurance / Q000502:physiology; D011388:Prolactin / Q000097:blood*; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult
chemical_list: D011388:Prolactin; D004298:Dopamine; D006854:Hydrocortisone
keywords: Central and peripheral fatigue; Dopaminergic activity; Motor accuracy; Motor task specificity; Perception