Twenty-four-hour rhythms of muscle strength with a consideration of some methodological problems

Abstract

The aim of the present study was to show the presence of circadian rhythm of muscle strength under a standardised protocol with controlled parameters to support suitable observation of variability during the day. Eight male volunteers were evaluated once a week for 6 weeks at six different times. Rectal temperature, peak torque (PT), maximum work and the average power of the flexor and extensor knee muscles in the isokinetic mode, as well as of PT in maximum voluntary isometric contraction of knee extensors at 60° knee flexion, were measured. The present study showed rhythms with a period of 24 hours in some indices of muscle strength performance at both speeds of movement and muscle groups. To our knowledge, this is the first study that has shown the presence of circadian rhythm in all speeds of movement and muscle groups tested under strict standardised protocol.

Keywords:

• daily rhythm
• muscle strength
• standardisation
• isokinetic movement