Circannual period of physical performance analysed by means of standard cosinor analysis: a case report.

Variation of physical fitness during the day is well investigated and is used both in athletes training as well as during sports contests. Circannual periodicities, on the other hand, seem to exist but have not been investigated systematically so far. The present case report shows that absolute increase in the number of press-ups varies during the year and can be modelled by means of standard cosinor analysis. Moreover, published data dealing with circannual rhythm of muscle strength could be fitted into a cosinor model. These results indicate a circannual increase of performance and warrant further controlled investigations. Due to methodological problems in trials for circannual rhythms, population cosinor models may be a suitable approach.