Glenda Bozett
02-28-2009, 08:38 AM
In the July issue of the International Journal of Sports Medicine, researchers examined peak strength at four different times of the day (7-8 am, 12-1 pm, 5-6 pm, 10:30-11:30 pm) for two consecutive days. The researchers reported that on 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 at 8-9 am, 1-2 pm, and 6-7 pm; peak strength was greatest between 6-7 pm. When they compared the percent increase from session to session, there was a 2.76% increase from the morning to afternoon session, but an 11.13% increase from the afternoon to the evening session5. Similar results were also reported in the Journal of Electromyography and Kinesiology where it was found that peak muscle strength was higher at 6 pm compared to 6 am4. The average increase in strength from morning to evening was 4.6%. 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 pm than at 6 am2, 3. This means much like there are changes in GH/cortisol throughout the day; it appears there are also circadian rhythms in strength during the day with strength being higher in the afternoon/early evening.
P.S. article published on MD Feb/ 27th. 2009
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 at 8-9 am, 1-2 pm, and 6-7 pm; peak strength was greatest between 6-7 pm. When they compared the percent increase from session to session, there was a 2.76% increase from the morning to afternoon session, but an 11.13% increase from the afternoon to the evening session5. Similar results were also reported in the Journal of Electromyography and Kinesiology where it was found that peak muscle strength was higher at 6 pm compared to 6 am4. The average increase in strength from morning to evening was 4.6%. 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 pm than at 6 am2, 3. This means much like there are changes in GH/cortisol throughout the day; it appears there are also circadian rhythms in strength during the day with strength being higher in the afternoon/early evening.
P.S. article published on MD Feb/ 27th. 2009