When Is The Best Time Of Day To Train?

It’s 8:00 a.m. and all the football players have arrived for preseason “max out” in the bench press, squat and power clean. Many of the players still look like they are not completely awake and others just seem stiff, yet they are expected to max out! I never understood when I was a strength coach why these sessions were scheduled so early in the morning, when the latest research suggests that maximal strength is best achieved in the afternoon.1
In the July issue of the International Journal of Sports Medicine, researchers examined peak strength at four different times of the day (7 a.m.-8 a.m., 12 p.m.-1 p.m., 5 p.m.-6 p.m., 10:30 p.m.-11:30 p.m.) for two consecutive days. The researchers reported that the morning values were significantly lower when compared to the rest of the day. There are many variables which can affect a lifter’s ability to generate peak force; however, none of the variables measured (sleep, stress level, normal circadian rhythms of the person, morning or night person) had a significant effect on the outcome. This study was similar to an earlier study, which had subjects perform peak isometric strength parameters from 8 a.m.-9 a.m., 1 p.m.-2 p.m. and 6 p.m.-7 p.m.; peak strength was greatest between 6 p.m.-7 p.m. When they compared the percent increase from session to session, there was a 2.76 percent increase from the morning to afternoon session, but an 11.13 percent increase from the afternoon to the evening session.5
Similar results were also reported in the Journal of Electromyography and Kinesiology. Researchers found that peak muscle strength was higher at 6 p.m. compared to 6 a.m.4 The average increase in strength from morning to evening was 4.6 percent. Clearly, this is not a psychological issue, yet more of a physiological condition. This is not the first study to demonstrate this effect; at least two other studies have demonstrated peak strength to be higher at 6 p.m. than at 6 a.m.2, 3 This means that much like there are changes in GH/cortisol throughout the day, there are also circadian rhythms in strength during the day, with strength being higher in the afternoon/early evening.

Temperature And Muscle Strength
The circadian rhythm amplitude of muscle strength has been found to range from 3.9 percent for the biceps muscles to 10.6 percent for the back muscles. So why is muscle strength higher in the afternoon compared to the morning? There is one physiological variable that seems to correlate with the peak increases in strength: body temperature. Body temperature is lowest in the morning and increases throughout the day. Muscular strength and body temperature appear to be associated by some researchers.6, 7 It is now recognized that torque and temperature vary during the day, but fluctuations in torque cannot be entirely explained by change in temperature. Maximal performance is generally improved by the end of the afternoon, at the peak of the body temperature curve.7, 8 Some studies have suggested that the simultaneous increases in both body temperature and muscular performance are causally related, and that the circadian rhythm of body temperature could be regarded as a passive warm-up effect.9