Most of the athletes have good days when they are full of strength and vitality but also bad days when they barely have enough energy to finish their usual workout. Are the hormonal changes that appear during the day responsible for these variations in performance?
The scientists from New Zealand and Australia discovered that the daily temperature variations of the body, but not those of testosterone and cortisol are influencing the performance on some exercises like the squats. The temperature of the body varies during the day and reaches the highest levels at the end of the afternoon. This time of the day is the most favorable for achieving top performance.
So when you choose the time of the workout you have to put in balance the following two elements: performance and coherence (the possibility of missing a workout). But of course this is just one of the ingredients of a successful workout... (The Journal of Strength and Conditioning 25: 1538-1545, 2011)
Article by Craig Wilson