Conventional wisdom says to train in the morning to kick off the day right and increase the chances of sticking to routine. However, research has uncovered evidence that training in the late afternoon provides the best results.

Psychological and physiological functions change relative to the time of the solar day. These changes are known as circadian rhythms. But what effect does this have on training performance over time?  A variety of studies found that short-term maximal performance peaks in the late afternoon between 4pm and 8pm due to body temperature. Researchers believe that the increase in core temperature may have a passive warm up effect which enhances metabolic reactions, increases extensibility of connective tissue, reduces muscle viscosity and increases the conduction velocity of action potentials.

Some studies attribute the difference in performance to hormones since hormone levels can fluctuate based on the time of day. Testosterone and growth hormone for example, are important for muscle growth. There is evidence that testosterone rises more after a late afternoon training session in comparison to a morning workout. For this reason alone, some experts have begun to recommend PM workouts. However, research still remains inconclusive about how much hormone fluctuations actually affect performance and long term results.

So, what time should you train? The subject is still being researched and there are surely pros and cons to every training time. In the end, it becomes a matter of convenience, personal preference and behavioral factors. Don’t let rigid guidelines tell you that you must train at one particular time – instead, customize your training time similar to the rest of your workout plan. Train at the time when you feel your best and perform your best.