Circadian variation of the effect of isometric strength training in man

Journal/Book: J. interdiscipl. Cycle Res. 19: 181 (1988).. 1988;

Abstract: (Institut für Arbeitsphysiologie and Rehabilitationsforschung der Philipps-Universität Marburg und Institut für kurmedizinische Forschung Bad Wildungen Marburg/Lahn FRG) In a first study four groups of healthy subjects (n-6-7) performed a 7-day muscular strength training of three different muscle groups (knee extensors. elbow extensors elbow flexors) by means of 10 maximal contractions of 6 sec duration wich 1 min intervals each day and that at four different times of day (3.00 9.00 15.00 21.00 h). In a second study eight groups of healthy subjects (n-4) performed a 1 -day muscular strength training of the elbow flexors using 20 maximal contractions of 6 sec duration with 1 min intervals at eight different times of day (3.00 6.00 9.00 h etc.). The training effects were followed up by means of 1 -sec maximal contractions during 3 weeks in the first study in most of the cases up to 7 weeks. The results of both experiments concerning the time of day effect were in good agreement showing maximal long-term training effects in the groups trained at 18.00 and 21.00 h whereas minimal effects were observed in the groups trained at 3.00 6.00 or 9.00 h. The circadian variation of the training effects started already at the first day after onset of training. It is concluded that not only processes of functional adaptation undergo circadian variations but also long-term processes of trophoplastic adaptation.

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