Best time of day to train

Body temperature starts to rise before waking,
reaches a peak at about 1800 hours, then falls
during sleep, with a nadir at around 0400
hours; an amplitude of 0.4–0.5°C is seen in
young adults.13 The circadian rhythm of body
temperature is mainly the result of fluctuations
in heat loss mechanisms rather than heat
production,13 maybe with the intervention of
noradrenergic peaks.14

components of
sports performance exhibit a rhythmic variation
during the day, with a peak in the early evening.
This time of day is characterised by peaks in
reaction time,25 isometric hand grip strength,26
elbow flexion strength,27 back strength,28 total
work performed in high intensity constant work
rate exercise,29 and lactate production,30 and
lowest levels of joint stiffness31 and pain
perception.32 When subjects are free to chose
their submaximal work rate during exercise of
less than 40 minutes duration, higher work rates
are achieved in the early evening without any
change in the perception of effort.33 Moreover,
in young adults, the mean work rate over 80
minutes of exercise was found to be higher in the
afternoon than in the morning.34 Improvements
in muscle strength after training sessions scheduled
in the evening have been found to be 20%
higher than those after training carried out in the
morning.35 Long term memory recall, in which
data must be retained for one week or longer, is
8% greater when the material is presented at
1500 hours than at 0900 hours.36 The implications
are important for the timing of coaching
instructions and strategy, since the 8% difference
in memory retention is similar to the
performance decrement induced when sleep is
restricted to three hours. When individual
differences in performances were controlled for,
a significant early evening peak was found for
length of jump37 and vertical jumping
performance.38 Swimming performance shows
an evening peak too,39 having rhythm amplitudes
of 11 to 14% of the 24 hour mean values. The
circadian variation in swimming performance is
greater than the effect of obtaining only three
hours of sleep for three successive nights.40 It has
to be stressed that there is an inverse relation
between speed and accuracy in a simple repetitive
test,41 with accuracy being worse in the early
evening. Remembering that other aspects of
performance—for example, mental arithmetic
and short term memory—peak in the early
morning rather than evening hours,42 it is possible
that times of day other than the evening may
be better for sports that demand accuracy, for
competitive strategies, and for delivery and
recall of coaching instructions.

phil s wrote:

This is a classic case of over-thinking. Just get out and train, honestly.