Us humans are in the main creatures of habit, we have a set routine of things that we like to do and try to keep to it as often as possible. Training in the gym is one of those routines, I know very few people who train at varying times during the week.
Mostly they are people like myself who have a crazy work schedule. Everyone else has their time to train (6am or 5pm for example) and you always know when to expect them. What’s interesting is how the body adapts to this routine, science tells us that there are people who are better suited to getting up early and there are people who are better suited to going to bed late. Getting your typical night-owl to train at 6am is probably not going to work out too well. Nor would getting your average early-bird to train at 10:30 at night.
This becomes abundantly clear when one of my regular clients does a training session at a different time than usual. So Colin who was knocking out a 180kg deadlift last session (at 6pm) but is now struggling to lift 120kg during a morning session. He has his training time, and really needs to stick to it! Find the right time for you to train, and try your hardest to stick to that routine. Because it can make a BIG difference to the results you get.
Something else that doesn’t get mentioned much when it comes to training is our Circadian rhythms. A study by Mora-Rodriguez et al (2012) discussed the effect of circadian rhythm on performance. Mentioning that power output normally decreases during the morning and increases in the early evening . Interestingly, the study found that caffeine was very effective of reversing the effect of Circadian rhythm on the body.
Matt ‘time to train’ Smith
 Mora-Rodriguez, R., Pallares, J., Lopez-Samanes, A., Ortega, J., Fernandez-Elias. 2012. Caffeine ingestion reverses the Circadian Rhythm effects on Neuromuscular performance in highly resistance-trained men. PLoS One 7(4): e33807