Night and Day

In the quest to maximize exercise results, athletes and fitness enthusiasts look at every exercise variable. Types of exercises, the frequency of exercise, rest periods, and so forth are studied to the nth degree. A recent study looked at the effects of circadian rhythm of cortisol(C) and testosterone(T) on maximal force production and power output. What did the study find?


The study concluded that, in general, strength and power training should be scheduled later in the day. There appears to be a relationship between the circadian rhythm of T and C with strength and power performance.


As you know, T promotes anabolism( promotion of protein synthesis within the muscular system) and C, the so-called "stress" hormone, is associated with muscle atrophy and strength loss. T and C levels ebb and flow throughout the day, so understanding these rhythms could help you exercise at the optimal time of day.


Without getting too technical, T and C levels were tested at 0800, 1200, 1600, and 2000. These levels showed a clear circadian rhythm, peaking at 0800 and reaching its lowest point at 2000 hours.


Rate of perceived exertion(RPE) is a measure of effort that is self-generated based upon a standardized scale. it helps the exerciser assess the intensity of their exercise session or individual exercise. RPE was significantly higher at 0800 and 2000 hours. This means that the exact same exercise seemed significantly harder at 0800 and 2000 hours than at the other times of day. And that can impact how hard you are able to exercise.


Of course, individuals vary, but, in general as core body temperatures rise throughout the day, physical performance improves. But if you can only exercise in the morning, by all means, do it. It's great for you both "Night and Day."


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