American Journal of Sports Science and Medicine, 2014, Vol. 2, No. 2, 65-69 Available online at http://pubs.sciepub.com/ajssm/2/2/2 © Science and Education Publishing DOI:10.12691/ajssm-2-2-2 Circadian Cycle and Its Influence on Parameters of Aerobic Training Ramon Cruz 1 , Francisco de Assis Manoel 2 , Bruno Pereira Melo 2 , Sandro Fernandes da Silva 3,* 1 Faculdade de Educação Física e Desporto, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil 2 Departamento de Educação Física, Universidade Estadual de Maringá, Maringá, Brazil 3 Departamento de Educação Física, Universidade Federal de Lavras, Lavras, Brazil *Corresponding author: sandrofs@gmail.com Received January 29, 2014; Revised March 05, 2014; Accepted March 09, 2014 Abstract Objectives: This study aims to evaluate the Influence of two distinct Periods of the day on maximal aerobic power in young Athletes mountain bike. Volunteers are the mountain bike Athletes, 37.83 ± 8.87 years, and underwent two progressive maximal exercise test on a cycle Ergometer at two times of day. Gauging the behavior glucose and heart rate. The verification of normality of data was performed by the Shapiro-Wilk test for analysis of variables was Adopted t test for paired samples. Statistical we Adopted an evidence for p <0.05. Results: Were the glucose threshold results not statistically significant. However trends indicating were there a better outcome in the evening. The maximal workload, maximal heart rate and glycemic load threshold. Conclusions: The results show trends on performance and circadian rhythm, and yet, the routine or team chosen for sensivity training appears to the circadian cycle. Keywords: circadian cycle, training and cycling Cite This Article: Ramon Cruz, Francisco de Assis Manoel, Bruno Pereira Melo, and Sandro Fernandes da Silva, “Circadian Cycle and Its Influence on Parameters of Aerobic Training.” American Journal of Sports Science and Medicine, vol. 2, no. 2 (2014): 65-69. doi: 10.12691/ajssm-2-2-2. 1. Introduction The performance variables physiological and psychological suffers interference of biological rhythms, which are cyclic changes that are regularly repeated in a given time interval generated in periods of 24 hours [1]. Some studies had been made identifying the influence of circadian cycle in determining variables on performance, as cardiovascular function [8], metabolic [9] and respiratory [2]. Physiological control of the circadian cycle is determined by changes in frequency environmental, and the light / dark cycle is one of the main synchronizers. Another way for the body to control their circadian mechanisms is necessary external and internal stimuli, acting as guides. These two pieces of information are transmitted to a biological oscillator, located in the suprachiasmatic nucleus of the hypothalamus, which acts as an integrator [3]. The interferon Consistency of the circadian cycle in human performance seems to follow the rhythm of body temperature [4,5]. Body temperature is often used as a marker rhythm, ease of measurement and its strong endogenous component. The minimum body temperature curve occurs during sleep, around 4:00 [7]. From this point, it starts increasing which increases upon awakening. After noon, there is a slight decrease, a phenomenon called post-lunch dip, then rise again, which leads to the occurrence of higher values at about 18:00 [9]. Similar to body temperature, heart function has also changes according to time of day, consistently lower at evening, independent of load, with a difference between day and night for 5-10 bpm. The HR max has been studied by different researchers [1,6]. In the literature we apply the cycle ergometer exercise at various times, such as: 2:00, 6:00, 10:00, 2:00pm, 6:00pm and 10:00pm and has been found that significant circadian variation in the Fc max [10]. Moreover, also the use of cycling were their used the time, 4:00, 8:00, 12:00, 3:00pm, 6:00pm, 9:00pm and 24:00 h [11], and in another study that found no significant differences between the different periods [5], used four times (8:00, 12:00, 4:00pm and 8:00pm) [5]. For best response to training, it is necessary to control some markers of performance. An important marker of human performance, VO 2MAX shows a circadian cycle of the interference [6] as well as other markers performance aerobic and anaerobic most [1,6] such as lactate, and the critical velocity (CV) [12]. The anaerobic threshold (AT) is a parameter widely used for exercise prescription and research in exercise physiology [13]. The AT can be determined by the behavior of blood lactate, which is a body's metabolic response to stress and that means a gradual transition between the energy systems [11]. Yet another method has been highlighted in order to identify the AT, which is the blood glucose response during progressive exercise [5]. But the blood glucose response has yet been the focus of many studies seeking its new relationship with other