Hormonal Circadian Rhythm

Discussion in 'Hypertrophy Research' started by ratty, Dec 17, 2008.

  1. ratty

    ratty New Member

    Chronobiol Int. 2004 Jan;21(1):131-46

    Influence of circadian time structure on acute hormonal responses to a single bout of heavy-resistance exercise
    in weight-trained men.

    Bird SP, Tarpenning KM.

    Both testosterone (T) and cortisol © exhibit circadian rhythmicity being highest in the morning and lowest in the evening. T is a potent stimulator of protein synthesis and may possess anti-catabolic properties within skeletal muscle, and C affects protein turnover, thereby altering the balance between hormone-mediated anabolic and catabolic activity. Physiological reactions of these hormones and training adaptations may influence the post-exercise recovery phase by modulating anabolic and catabolic processes, therefore affecting metabolic equilibrium, and may lead to intensification of catabolic processes. We investigated the effect of the circadian system on the T and C response of weight-trained men to heavy resistance exercise. Thirteen young (21.8 +/- 2.2 yr) weight-trained men (12 months training experience) performed an eight-station heavy-resistance exercise protocol on two separate occasions (AM: 06:00 h and PM: 18:00 h), completing 3 sets of 8-10 repetitions at 75% of each subject's one-repetition maximum (1-RM). Blood samples were obtained prior to, during, and following the exercise bout, and serum total T and C concentrations were determined by competitive immunoassay technique. Performing the single bout of heavy-resistance exercise in the PM as compared to the AM positively altered the C and T/C ratio hormonal response. Pre-exercise C concentrations were significantly lower (p < 0.05) in the PM session, which resulted in a lower peak value, and the accompanying increased T/C ratio suggested a reduced catabolic environment. These data demonstrate that the exercise-induced hormonal profile can be influenced by the circadian time structure toward a profile more favorable for anabolism, therefore optimizing skeletal muscle hypertrophic adaptations associated with resistance exercise.

    wondered if anyone has looked at circadian rhythm before? and how significant you think it is for training?

    I found this journal, but couldnt find any studies which monitor chronic strength and size adaptations, which i am doing for my BSc project...
  2. dkm1987

    dkm1987 New Member

    search for these authors
    Ahtiainen JP
    Kraemer WJ
    Häkkinen K
    Smilios I
    Raastad T

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