Can the knowledge of chronotype be useful for the motivation and the training plans?

Introduction: General knowledge of “time of day” effects on exercise might not be enough, since everyone can have a different circadian propensity (chronotype) based on their position on a Morningness- Eveningness Scale (ranges from a morning-type = M-type to evening- type = E-type, or neither-type = N-type) (3). In this project we studied the response to the same physical activity performed in the morning and evening by different chronotypes. Methods: Each of 22 subjects (12 males and 10 females, age: 23.2 ± 3.6, BMI: 22.45 ± 2.7) filled out the Horne-Ostberg Morningness- Eveningness Questionnaire (MEQ) and the results have been com- pared to the Morningness-Eveningness Scale to determine their chronotype (3). They then performed, at their own voluntary speed, a walking session, consisting of three repetitions uphill and downhill, first in the late afternoon at 16:30h and then the next morning at 8:30h. The performance time was recorded by an EKT-orienteering system. Each subject wore a HR monitor (PolarTeam 2) to record their HR during each entire walking session and reported their perceived exer- tion (Borg scale 6-20) upon completion (1). Results: MEQ= 14 N-types, 4 E-types and 4 M-types. Results from one M-type, one E-type and two N-types (as controls) are discussed in detail for the case-study. The M-type walked faster in the morning than in the late afternoon, but showed no difference in HR response. Conversely, the E-type walked faster in the evening than in the morn- ing, with similar HR in both sessions. The N-types showed increased HR when performance time decreased. Conclusion: This case-study showed that response to physical activi- ty can be influenced by chronotype, in agreement with other reports in the literature (2),(4). While a follow-up study with more subjects is necessary, the results suggest that when trying to increase the health and well-being in the population, it would be advisable to arrange physical activity classes both in the morning and in the evening, and have the public join the classes according to their chronotype to achieve the most benefit. References 1. Borg, G. A. (1982). Psychophysical bases of percieved exertion. Medicine and Science In Sports and Exercise, 14(5), 377-381 2. Brown, F. M., Neft, E. E., & LaJambe, C. M. (2008). Collegiate rowing crew performance varies by morningness-eveningness. J Strength Cond Res, 22(6), 1894-1900 3. Horne, J. A., & Ostberg, O. (1976). A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms. Int J Chronobiol, 4(2), 97-110 4. Sugawara, J., Hamada, Y., Nishijima, T., & Matsuda, M. (2001). Diurnal variations of post-exercise parasympathetic nervous reacti- vation in different chronotypes. Jpn Heart J, 42(2), 163-171