Evening chronotype predicts dropout of physical exercise: a prospective analysis.

Purpose: Eveningness preference to sleep/wake and perform physical/cognitive activities has been associated with worse health outcomes, when compared to morningness preference. Physical activity is one potential mediator that could explain this relationship; however, most of these evidences come from cross-sectional design studies. Our goal was to assess whether chronotype could predict the risk of dropout of physical exercise programs. Methods: We followed 153 newly enrolled volunteers at three different gyms, from both sexes, aged between 18 and 65 years, during 12 weeks. The daily frequency of exercises in the programs was objectively measured (gym's electronic turnstiles). Using questionnaires, we collected data of variables related to demographic characteristics, health, physical activity, sleep, anthropometric and chronobiological parameters (Morningness-Eveningness Questionnaire-MEQ). Two multivariate models were created using Cox regression analysis to test the risk of dropout of physical exercise practice. Both models accounted for age, educational level, civil status, membership plan duration, physical exercise practice frequency during week 1 and chronotype (MEQ score and chronotypes). Results: Model 1 results showed that higher MEQ score was associated with a lower chance of quitting the program (HR = 0.98; CI95% 0.95-1.00; p = 0.046). Considering the chronotypes, E-types showed the highest dropout risk compared to that of M-types (HR = 2.22; CI95% 1.09-4.52; p = 0.027). Conclusion: Our results suggest that chronotype is another variable to be considered in future studies on promoting PAs in formal environments. Likewise, the practice frequency during week 1 and duration of membership plan also deserve more attention in additional studies.

Worse sleep quality predicts early drop out from physical exercise programs.

Introduction and Objective: Sleep quality (SQ) benefits from regular physical exercise (PE) practice, but the effect of SQ over behavioral aspects of PE is not well known. In this study, we tested whether sleep variables can predict the drop out risk for PE programs during a six-week critical period for habit formation at gyms. Material and Methods: We assessed 153 volunteers, freshly enrolled at three different gyms and from both sexes, with average age of 33.6 (±11.9) years. Questionnaires provided sociodemographic, health, sleep, physical activity and circadian rhythmicity information. Daily PE practice frequency was monitored using the gym's turnstiles electronic records. We created a multivariate model using Cox regression in order to test the risk of PE program drop out during the first six weeks. Results: Worse SQ predicted a higher drop out risk (HR=1.11; 95%CI = 1.02-1.21; p<0.05), even when adjusted for other potential confounding variables. Conclusion: We found that worse SQ predicted a higher early drop out from PE programs in the formal context of gyms during the first six weeks, along with other variables related to PE practice.

Sincronização não-fótica: o efeito do exercício físico aeróbio: [revisão] / Non-photic synchronization: the effect of aerobic physical exercise: [review]

As principais alterações, agudas e crônicas, provocadas pelo exercício físico aeróbio (EF) sobre o organismo são, de maneira geral, bem conhecidas. No entanto, existe um efeito em particular do EF que começou a ser elucidado no começo da década de 90, em humanos, que tem a capacidade de alterar a relação temporal do organismo com o meio. A modificação da expressão dos ritmos circadianos, causada pelo EF, qualifica-o como sincronizador dos osciladores biológicos. O principal sincronizador da ritmicidade biológica é o ciclo geofísico claro/escuro. A alternância do dia e da noite, através de diferenças nos níveis de luminosidade, é percebida por meio de vias fóticas pelo sistema de temporização circadiana (STC). Esses estímulos, chamados fóticos, fornecem informações temporais para o STC sincronizando os osciladores biológicos com esse ciclo ambiental. Outros estímulos também são capazes de sincronizá-los e são chamados de sincronizadores não-fóticos. Esta revisão aborda o efeito do EF sobre o sistema de temporização e, ao mesmo tempo, discute as possíveis e prováveis aplicações cronobiológicas dos conhecimentos abordados. O EF pode afetar o STC através de vias não-fóticas, podendo beneficiar a saúde de indivíduos em diversas situações, tais como vôos transmeridianos, trabalhos noturnos e distúrbios do sono. Ressalta-se, também, que devem ser realizados mais estudos no cotidiano das pessoas para compreender melhor a relação entre, e a contribuição dos, diferentes sincronizadores em um contexto real.

The main alterations, either acute or chronic, caused by aerobic physical exercise (PE) over the body are generally well-known. However, there is a particular effect of PE which started to be elucidated in the beginning of the 90's in humans which has the capacity to alter the temporal relationship of the body with the environment. The modification of the expression of the circadian rhythms caused by PE qualifies it as a synchronizer of the biological oscillators. The main synchronizer of the biological rhythm is the light/dark geophysical cycle. The day/night rotation which occurs through differences in the luminosity levels is perceived through photic ways by the CTS. These stimuli, called photic, provide temporal information to the CTS synchronizing hence the biological oscillators to this environmental cycle. Other stimuli are also capable to synchronize them and are called non-photic synchronizers. This review writes about the effect of PE over the temporization system as well as discusses the possible and probable chronobiological applications of the mentioned knowledge. PE may affect the CTS through non-photic ways, being hence able to benefit health of individuals in several situations, such as transmeridian flights, night shift tasks and sleep disturbs. Moreover, we highlight that further studies should be conducted on individuals' routine in order to better understand the relationship between different synchronizers as well as their contribution in a real context.

Freqüência cardíaca máxima em esteira ergométrica em diferentes horários / Frecuencia cardíaca máxima en cinta ergométrica a diferentes horarios / Maximal heart rate on treadmill at different times

Como muitas medidas do desempenho humano apresentam variações circadianas que parecem acompanhar o ritmo da temperatura corporal, o objetivo deste estudo foi comparar a freqüência cardíaca máxima (FCmax) no teste de Bruce (Tbruce) em diferentes horários do dia. Foram estudados 11 indivíduos do gênero masculino, com 22,0 ± 1,6 anos, fisicamente ativos e do cronotipo intermediário. Observaram-se FC de repouso (FCrep), FC máxima (FCmax), percepção de esforço (PE) e tempo até a exaustão (TBruce). Para medir a FC, foi utilizado o cardiofreqüencímetro Polar Vantage NV. A PE foi obtida pela escala de Borg (6-20). Aplicou-se o protocolo de Bruce para esteira ergométrica, até a exaustão, em seis horários distintos: 9:00, 12:00, 15:00, 18:00, 21:00 e 24:00 horas. Os resultados foram submetidos à análise de variância para medidas repetidas, seguida do teste de Tukey (p < 0,05) e ao ajuste Cosinor para identificação de padrões rítmicos. Houve diferença significativa entre a FCrep das 15:00 e 24:00 horas (67,2 ± 6,9 e 60,4 ± 6,4bpm) e na FCmax das 12:00 e 24:00 horas (197,4 ± 7,9 e 191,3 ± 5,8bpm). Não foi observada diferença na PE e no TBruce. Foi encontrada ritmicidade em um indivíduo na FCrep, um na FCmax e dois no TBruce. Concluiu-se que, em condições não controladas, mantendo-se as atividades diárias, tanto a FCrep quanto a Fcmax apresentam valores mais baixos por volta das 24:00 horas, sem perda no desempenho aeróbio máximo e sem alteração da PE. Esses achados devem ser considerados na avaliação aeróbia e na prescrição de exercícios em horários mais tardios.

The aim of this study was to compare the maximal heart rate (HRmax) in the Bruce test (TBruce) at different times of the day, since several measurements of the human performance present circadian variations which seem to follow the body temperature rhythm. Eleven male individuals, with 22.0 ± 1.6 years, physically active and from the intermediate chronotype were studied. The resting HR (HRres), maximal HR (HRmax), perceived exertion (PE) and time until exhaustion (TBruce) were observed. The Polar Vantage NV cardiofrequencymeter was used in order to measure the HR. The PE was obtained through the Borg's scale (6-20). The protocol by Bruce for treadmill was applied until exhaustion, at 6 different times: 9:00; 12:00; 15:00; 18:00; 21:00 and 24:00 hours. The results were submitted to the variance analysis for repeated measurements, followed by Tukey test (p < 0.05) and the Cosinor adjustment for identification of rhythmic patterns. There was significant difference between the HRres of the 15:00 and 24:00 h (67.2 ± 6.9 and 60.4 bpm) and in the HR max of the 12:00 and 24:00 hours (197.4 ± 7.9 and 191.3 ± 5.8 bpm). No difference was identified in the PE and in the TBruce. Rhythmicity was found in 1 individual in the HRres, 1 in the HRmax and 2 in the TBruce. It was concluded that in uncontrolled conditions, whenever daily activities are kept, both HRres and HRmax present lower indices around 24:00 hours, with no loss in the maximal aerobic performance and no PE alteration. These findings should be considered in the aerobic evaluation and in the exercises prescription at later times.

Debido a que muchas medidas de desempeño humano presentan variaciones circadianas que parecen acompañar el ritmo de la temperatura corporal, el objetivo de este estudio ha sido el de comparar la frecuencia cardíaca máxima (FCmax) en el test de Bruce (TBruce) en diferentes horarios del día. Fueron estudiados 11 individuos del género masculino, con 22,0 ± 1,6 años, físicamente activos y de cronotipo intermedio. Se observó la FC de reposo (FCrep), FC máxima (FCmax), percepción de esfuerzo (PE) y tiempo hasta la extenuación (TBruce). Para medir la FC se usó el cardiofrecuencímetro Polar Vantage NV. La PE se obtuvo por la escala de Borg (6-20). Se aplicó el protocolo de Bruce para cinta ergométrica, hasta la extenuación, en 6 horarios distintos: 9:00, 12:00, 15:00, 18:00, 21:00 y 24:00 horas. Los resultados fueron sometidos a análisis de varianza para medidas repetidas, seguida del test de Tukey (p < 0,05) y al ajuste Cosinor para identificación de los padrones rítmicos. Hubo diferencia significativa entre la FCrep de las 15:00 y 24:00 h (67,2 ± 6,9 y 60,4 ± 6,4 bpm) y en la FCmax de las 12:00 y 24:00 horas (197,4 ± 7,9 y 191,3 ± 5,8 bpm). No fue observada diferencia en la PE y en el TBruce. Se encontró ritmo en 1 individuo en la FCrep, 1 en la FCmax y 2 en el TBruce. A partir de esto se concluyó que, en condiciones no controladas, manteniéndose las actividades diarias, tanto la FCrep, como la Fcmax, presentan valores más bajos alrededor de las 24:00 horas, sin pérdida en el desempeño aeróbico máximo y sin alteración de PE. Estos resultados deben ser considerados en la evaluación aeróbica y en la prescripción de ejercicios en horarios más tardíos.