Diurnal variation in maximal and submaximal strength, power and neural activation of leg extensors in men: multiple sampling across two consecutive days

Int J Sports Med. 2008 Mar;29(3):217-24. doi: 10.1055/s-2007-965125. Epub 2007 Jul 5.


This study aimed to compare day-to-day repeatability of diurnal variation in strength and power. Thirty-two men were measured at four time points (07 : 00 - 08 : 00, 12 : 00 - 13 : 00, 17 : 00 - 18 : 00, and 20 : 30 - 21 : 30 h) throughout two consecutive days (day 1 and day 2). Power during loaded squat jumps, torque and EMG during maximal (MVC) and submaximal (MVC40) voluntary isometric knee extension contractions were measured. The EMG/torque ratio during MVC and MVC40 was calculated to evaluate neuromuscular efficiency. A significant time-of-day effect with repeatable diurnal patterns was found in power. In MVC, a significant time-of-day effect was present on day 2, whereas day 1 showed a typical but nonsignificant diurnal pattern. EMG and antagonist co-activation during MVC remained statistically unaltered, whereas neuromuscular efficiency improved from day 1 to day 2. A similar trend was observed in MVC40 neuromuscular efficiency with significant time-of-day and day-to-day effects. Unaltered agonist and antagonist activity during MVC suggests that modification at the muscular level was the primary source for the diurnal variation in peak torque. A learning effect seemed to affect data in MVC40. In conclusion, the second consecutive test day showed typical diurnal variation in both maximum strength and power with no day-to-day effect of cumulative fatigue.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Body Temperature / physiology
  • Circadian Rhythm / physiology*
  • Electromyography
  • Humans
  • Isometric Contraction / physiology
  • Lower Extremity / physiology*
  • Male
  • Motor Neurons / physiology*
  • Muscle Fatigue / physiology
  • Muscle Strength / physiology*
  • Muscle, Skeletal / innervation
  • Muscle, Skeletal / physiology*
  • Torque