PMID- 21273912
OWN - NLM
STAT- MEDLINE
DCOM- 20110921
LR  - 20161018
IS  - 1533-4287 (Electronic)
IS  - 1064-8011 (Linking)
VI  - 25
IP  - 6
DP  - 2011 Jun
TI  - The effects of circadian rhythmicity of salivary cortisol and testosterone on 
      maximal isometric force, maximal dynamic force, and power output.
PG  - 1538-45
LID - 10.1519/JSC.0b013e3181da77b0 [doi]
AB  - The study investigated the effects of circadian rhythm of cortisol (C) and 
      testosterone (T) on maximal force production (Fpeak) and power output (Ppeak). 
      Twenty male university students (mean age = 23.8 +/- 3.6 years, height = 177.5 +/- 
      6.4 cm, weight = 78.9 +/- 11.2 kg) performed 4 time-of-day testing sessions 
      consisting of countermovement jumps (CMJs), squat jumps (SJ), isometric midthigh 
      pulls (IMTPs), and a 1-repetition maximum (1RM) squat. Saliva samples were 
      collected at 0800, 1200, 1600, and 2000 hours to assess T and C levels on each 
      testing day. Session rate-of-perceived exertion (RPE) scores were collected after 
      each session. The results showed that Fpeak and Ppeak presented a clear circadian 
      rhythm in CMJ and IMTP but not in SJ. One repetition maximum squat did not 
      display a clear circadian rhythm. Session RPE scores collected at 0800 and 2000 
      hours were significantly (p </= 0.05) higher than those obtained at 1200 and 1600 
      hours. Salivary T and C displayed a clear circadian rhythm with highest values at 
      0800 hours and lowest at 2000 hours; however, no significant correlation was 
      found between T and C with Fpeak and Ppeak. A very strong correlation was found 
      between Taural with Fpeak of CMJ and IMTP and Ppeak of CMJ (r = 0.86, r = 0.84 
      and r = 0.8, p </= 0.001). The study showed the existence of a circadian rhythm in 
      Fpeak and Ppeak in CMJ and IMTP. The evidence suggests that strength and power 
      training or testing should be scheduled later during the day. The use of Taural 
      seemed to be a more effective indicator of physical performance than hormonal 
      measures, and the use of session RPE should also be closely monitored because it 
      may present a circadian rhythm.
FAU - Teo, Weipeng
AU  - Teo W
AD  - Exercise and Sports Science Department, School of Exercise, Biomedical and Health 
      Sciences, Edith Cowan University, Joondalup, Australia. weipeng.teo@ecu.edu.au
FAU - McGuigan, Michael R
AU  - McGuigan MR
FAU - Newton, Michael J
AU  - Newton MJ
LA  - eng
PT  - Journal Article
PT  - Randomized Controlled Trial
PL  - United States
TA  - J Strength Cond Res
JT  - Journal of strength and conditioning research
JID - 9415084
RN  - 3XMK78S47O (Testosterone)
RN  - WI4X0X7BPJ (Hydrocortisone)
SB  - IM
MH  - Adult
MH  - Circadian Rhythm/*physiology
MH  - Humans
MH  - Hydrocortisone/analysis/*physiology
MH  - Isometric Contraction/*physiology
MH  - Leg/physiology
MH  - Male
MH  - Muscle Strength/*physiology
MH  - Muscle, Skeletal/*physiology
MH  - Saliva/chemistry/*physiology
MH  - Testosterone/analysis/*physiology
MH  - Weight Lifting/physiology
MH  - Young Adult
EDAT- 2011/01/29 06:00
MHDA- 2011/09/22 06:00
CRDT- 2011/01/29 06:00
PHST- 2011/01/29 06:00 [entrez]
PHST- 2011/01/29 06:00 [pubmed]
PHST- 2011/09/22 06:00 [medline]
AID - 10.1519/JSC.0b013e3181da77b0 [doi]
PST - ppublish
SO  - J Strength Cond Res. 2011 Jun;25(6):1538-45. doi: 10.1519/JSC.0b013e3181da77b0.