title: Free-running circadian rhythms of muscle strength, reaction time, and body temperature in totally blind people.
abstract: Light is the major synchronizer of circadian rhythms. In the absence of light, as for totally blind people, some variables, such as body temperature, have an endogenous period that is longer than 24 h and tend to be free running. However, the circadian rhythm of muscle strength and reaction time in totally blind people has not been defined in the literature. The objective of this study was to determine the period of the endogenous circadian rhythm of the isometric and isokinetic contraction strength and simple reaction time of totally blind people. The study included six totally blind people with free-running circadian rhythms and four sighted people (control group). Although the control group required only a single session to determine the circadian rhythm, the blind people required three sessions to determine the endogenous period. In each session, isometric strength, isokinetic strength, reaction time, and body temperature were collected six different times a day with an interval of at least 8 h. The control group had better performance for strength and reaction time in the afternoon. For the blind, this performance became delayed throughout the day. Therefore, we conclude that the circadian rhythms of strength and simple reaction time of totally blind people are within their free-running periods. For some professionals, like the blind paralympic athletes, activities that require large physiological capacities in which the maximum stimulus should match the ideal time of competition may result in the blind athletes falling short of their expected performance under this free-running condition.
authors.affiliation: Universidade Estadual do Sudoeste da Bahia, Rua José Moreira Sobrinho, s/n, Zipcode 45206-190, Jequiezinho, Jequié, BA, Brazil. csquarcini@gmail.com
authors.forename: Camila Fabiana Rossi
authors.initials: CF
authors.lastname: Squarcini
authors.forename: Maria Laura Nogueira
authors.initials: ML
authors.lastname: Pires
authors.forename: Cleide
authors.initials: C
authors.lastname: Lopes
authors.forename: Ana Amélia
authors.initials: AA
authors.lastname: Benedito-Silva
authors.forename: Andrea Maculano
authors.initials: AM
authors.lastname: Esteves
authors.forename: Germaine
authors.initials: G
authors.lastname: Cornelissen-Guillaume
authors.forename: Carolina
authors.initials: C
authors.lastname: Matarazzo
authors.forename: Danilo
authors.initials: D
authors.lastname: Garcia
authors.forename: Maria Stella Peccin
authors.initials: MS
authors.lastname: da Silva
authors.forename: Sergio
authors.initials: S
authors.lastname: Tufik
authors.forename: Marco Túlio
authors.initials: MT
authors.lastname: de Mello
mesh_terms: D000328:Adult; D001683:Biological Clocks; D001833:Body Temperature Regulation; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011930:Reaction Time