The Effects of Circadian Rhythmicity of Salivary Cortisol and Testosterone on Maximal Isometric Force, Maximal Dynamic Force, and Power Output

Teo, W, McGuigan, MR, and Newton, MJ. The effects of circadian rhythmicity of salivary cortisol and testosterone on maximal isometric force, maximal dynamic force, and power output. J Strength Cond Res 25(6): 1538-1545, 2011—

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.

I have found that using cortisol (C) and testosterone (T) testing with athletes has given me new insight into performance and recovery and this piece of research I find very interesting.

Effects of Saddle Height on Economy and Anaerobic Power in Well-Trained Cyclists

Effects of Saddle Height on Economy and Anaerobic Power in Well-Trained Cyclists

Peveler, WW and Green, JM. Effects of saddle height on economy and anaerobic power in well-trained cyclists. J Strength Cond Res 25(3): 629-633, 2011-In cycling, saddle height adjustment is critical for optimal performance and injury prevention.

A 25-35° knee angle is recommended for injury prevention, whereas 109% of inseam, measured from floor to ischium, is recommended for optimal performance. Previous research has demonstrated that these 2 methods produce significantly different saddle heights and may influence cycling performance. This study compared performance between these 2 methods for determining saddle height. Subjects consisted of 11 well-trained (V̇o2max = 61.55 ± 4.72 ml·kg−1·min−1) male cyclists. Subjects completed a total of 8 performance trials consisting of a graded maximal protocol, three 15-minute economy trials, and 4 anaerobic power trials. Dependent measures for economy (V̇o2, heart rate, and rating of perceived exertion) and anaerobic power (peak power and mean power) were compared using repeated measures analysis of variance (α = 0.05). V̇o2 was significantly lower (reflecting greater economy) at a 25° knee angle (44.77 ± 6.40 ml·kg−1·min−1) in comparison to a 35° knee angle (45.22 ± 6.79 ml·kg−1·min−1) and 109% of inseam (45.98 ± 5.33 ml·kg−1·min−1). Peak power at a 25° knee angle (1,041.55 ± 168.72 W) was significantly higher in relation to 109% of inseam (1,002.05 ± 147.65 W). Mean power at a 25° knee angle (672.37 ± 90.21 W) was significantly higher in relation to a 35° knee angle (654.71 ± 80.67 W). Mean power was significantly higher at 109% of inseam (662.86 ± 79.72 W) in relation to a 35° knee angle (654.71 ± 80.67 W). Use of 109% of inseam fell outside the recommended 25-35° range 73% of the time. Use of 25° knee angle appears to provide optimal performance while keeping knee angle within the recommended range for injury prevention.

Not sure about this study.....looking for a comment by my friend Paraic McGlynn

Update:

I talked to Praic McGlynn the famed bike fitter from serotta that I trained under and he is working on some comments about this study. This article is a hot topic on my blog page and has gotten a ton of traffic so if you have an opinion then please leave a comment.

Relationship Between Strength, Power, Speed, and Change of Direction Performance of Female Softball Players

Relationship Between Strength, Power, Speed, and Change of Direction Performance of Female Softball Players

by Nimphius, Sophia; Mcguigan, Michael R; Newton, Robert U
Nimphius, S, McGuigan, MR, and Newton, RU. Relationship between strength, power, speed and change of direction performance of female softball players. J Strength Cond Res 24(4): 885-895, 2010-The purpose of this study was to investigate (a) the cross-sectional relationship of strength, power, and performance variables in trained female athletes and (b) determine if the relationship between these variables changes over the course of a season. Ten female softball players (age = 18.1 +/- 1.6 years, height = 166.5 +/- 8.9 cm, and weight = 72.4 +/- 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (one repetition maximum [1RM]), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, unloaded countermovement vertical jump height (VJH) 1 base and 2 base sprint performance and change of direction performance on dominant and nondominant sides. The testing sessions occurred pre, mid, and post a 20-week training period. Relationship between body weight (BW), relative strength (1RM/BW), VJH, relative PP, relative PF, PV, speed, and change of direction variables were assessed by Pearson product-moment correlation coefficient at each testing session. Significant relationships were found across all time points with BW, speed, and change of direction measures (r = 0.70-0.93) and relative strength and measures of speed and change of direction ability (r = -0.73-0.85). There were no significant relationships between VJH and any measure of performance at any time point. In conclusion, BW and relative strength have strong to very strong correlations with speed and change of direction ability, and these correlations remain consistent over the course of the season. However, it seems as if many relationships vary with time, and their relationships should therefore be investigated longitudinally to better determine if these cross-sectional relationships truly reflect a deterministic relationship. (C) 2010 National Strength and Conditioning Association
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