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Circadian Rhythms



Senior Member
Oct 21, 2010
This furthered my ideas in believing specific time-of-day environments certainly do have an effect in an individuals overall performance and optimal adaptation is possible. The relationship between the circadian rhythms and the roll it plays C/T levels is interesting. If anyone has anything to input in regards to when they "feel" is the best time for them to train, please discuss if you wish. I'd like to hear more opinions on the majority of our members here and when/why they train when they do. Should be interesting.

"Chronobiol Int. 2010 Jun;27(4):675-705.
Interactions of cortisol, testosterone, and resistance training: influence of circadian rhythms.

Hayes LD, Bickerstaff GF, Baker JS.

Department of Exercise and Sports Science, University of the West of Scotland, Almada Street, Hamilton, Scotland, UK. [email protected]

Diurnal variation of sports performance usually peaks in the late afternoon, coinciding with increased body temperature. This circadian pattern of performance may be explained by the effect of increased core temperature on peripheral mechanisms, as neural drive does not appear to exhibit nycthemeral variation. This typical diurnal regularity has been reported in a variety of physical activities spanning the energy systems, from Adenosine triphosphate-phosphocreatine (ATP-PC) to anaerobic and aerobic metabolism, and is evident across all muscle contractions (eccentric, isometric, concentric) in a large number of muscle groups. Increased nerve conduction velocity, joint suppleness, increased muscular blood flow, improvements of glycogenolysis and glycolysis, increased environmental temperature, and preferential meteorological conditions may all contribute to diurnal variation in physical performance. However, the diurnal variation in strength performance can be blunted by a repeated-morning resistance training protocol. Optimal adaptations to resistance training (muscle hypertrophy and strength increases) also seem to occur in the late afternoon, which is interesting, since cortisol and, particularly, testosterone (T) concentrations are higher in the morning. T has repeatedly been linked with resistance training adaptation, and higher concentrations appear preferential. This has been determined by suppression of endogenous production and exogenous supplementation. However, the cortisol (C)/T ratio may indicate the catabolic/anabolic environment of an organism due to their roles in protein degradation and protein synthesis, respectively. The morning elevated T level (seen as beneficial to achieve muscle hypertrophy) may be counteracted by the morning elevated C level and, therefore, protein degradation. Although T levels are higher in the morning, an increased resistance exercise-induced T response has been found in the late afternoon, suggesting greater responsiveness of the hypothalamo-pituitary-testicular axis then. Individual responsiveness has also been observed, with some participants experiencing greater hypertrophy and strength increases in response to strength protocols, whereas others respond preferentially to power, hypertrophy, or strength endurance protocols dependent on which protocol elicited the greatest T response. It appears that physical performance is dependent on a number of endogenous time-dependent factors, which may be masked or confounded by exogenous circadian factors. Strength performance without time-of-day-specific training seems to elicit the typical diurnal pattern, as does resistance training adaptations. The implications for this are (a) athletes are advised to coincide training times with performance times, and (b) individuals may experience greater hypertrophy and strength gains when resistance training protocols are designed dependent on individual T response."

Circadian Rhythms


Dec 21, 2010
Damn hp you're everywhere I go lol.

Great post.

I like to lift in the evening. I tried a morning routine and it was short lived. Besides lack of motivation from not being a morning person I feel I gain better after having a days worth of meals in. It may be psycological but if I don't get atleast 3-4 good meals in before the gym I feel weak and sluggish.