Chronotype and response to training during the polar night: a pilot study

Background: An individual's chronotype influences his or her physiological rhythms. Some studies have looked at the effect of time of day on the responses to exercise, but studies on the effect of long-term training are lacking. Objective: To report the effects of an 8-week training period during the polar night in nonathletes of different chronotypes living at 70 degrees N. Design: In all, 10 morning (M), 10 neither (N) and 10 evening (E) types were recruited, and their aerobic capacity (VO2max), strength, flexibility and balance before and after the training period were tested. Results: 3 E-types, 5 N-types and 6 M-types completed the protocol. An increase in VO2max and strength was observed for the whole group. The best negative correlation (r=-0.5287) was found between the Morningness-Eveningness Questionnaire (MEQ) score and the increase in VO2max, and the best positive correlation (r=0.4395) was found between MEQ and the increase in strength. Changes in balance and flexibility did not show any clear trends. Conclusion: In an environment with no outdoor daylight, it seems that the response to 8 weeks of aerobic training is larger in the E-than in the M-types, although the M-types showed a larger improvement in strength.