New article published

Finally, our review on the role of Testosterone and Cortisol in modulating training responses in athletes has been published on Sports Medicine.

 

Here are the details:

Sports Med. 2011 Feb 1;41(2):103-23. doi: 10.2165/11539170-000000000-00000.

Two Emerging Concepts for Elite Athletes: The Short-Term Effects of Testosterone and Cortisol on the Neuromuscular System and the Dose-Response Training Role of these Endogenous Hormones.

Crewther BT, Cook C, Cardinale M, Weatherby RP, Lowe T.

The New Zealand Institute for Plant Food Research Limited, Hamilton, New Zealand.

Abstract

The aim of this review is to highlight two emerging concepts for the elite athlete using the resistance-training model: (i) the short-term effects of testosterone (T) and cortisol (C) on the neuromuscular system; and (ii) the dose-response training role of these endogenous hormones. Exogenous evidence confirms that T and C can regulate long-term changes in muscle growth and performance, especially with resistance training. This evidence also confirms that changes in T or C concentrations can moderate or support neuromuscular performance through various short-term mechanisms (e.g. second messengers, lipid/protein pathways, neuronal activity, behaviour, cognition, motor-system function, muscle properties and energy metabolism). The possibility of dual T and C effects on the neuromuscular system offers a new paradigm for understanding resistance-training performance and adaptations. Endogenous evidence supports the short-term T and C effects on human performance. Several factors (e.g. workout design, nutrition, genetics, training status and type) can acutely modify T and/or C concentrations and thereby potentially influence resistance-training performance and the adaptive outcomes. This novel short-term pathway appears to be more prominent in athletes (vs non-athletes), possibly due to the training of the neuromuscular and endocrine systems. However, the exact contribution of these endogenous hormones to the training process is still unclear. Research also confirms a dose-response training role for basal changes in endogenous T and C, again, especially for elite athletes. Although full proof within the physiological range is lacking, this athlete model reconciles a proposed permissive role for endogenous hormones in untrained individuals. It is also clear that the steroid receptors (cell bound) mediate target tissue effects by adapting to exercise and training, but the response patterns of the membrane-bound receptors remain highly speculative. This information provides a new perspective for examining, interpreting and utilizing T and C within the elite sporting environment. For example, individual hormonal data may be used to better prescribe resistance exercise and training programmes or to assess the trainability of elite athletes. Possible strategies for acutely modifying the hormonal milieu and, thereafter, the performance/training outcomes were also identified (see above). The limitations and challenges associated with the analysis and interpretation of hormonal research in sport (e.g. procedural issues, analytical methods, research design) were another discussion point. Finally, this review highlights the need for more experimental research on humans, in particular athletes, to specifically address the concept of dual steroid effects on the neuromuscular system.

Sleep and teenagers

Sleep (or lack of…) is an interesting topic. Quality of sleep has been shown to negatively affect human performance for various reasons. Furthermore, there have been numerous reports suggesting a link between lack of sleep and depression.

The relationship between short sleep duration and depression has been suggested to be bidirectional,¹ with chronic partial sleep deprivation being a potential risk factor for depression. Cross-sectional studies have found relationships between inadequate sleep and depression in adolescents,^2,3 and a longitudinal study has shown that getting less sleep over time increased the symptoms of depression among middle school students.⁴ Short sleep duration has also been shown to be associated with suicidal ideation⁵ and suicidal behavior⁶ in adolescents and adults⁷ in cross-sectional studies.

A recent quasi-experimental study conducted by Gangwish et al. (2010) has looked at the relationships between parental set bedtimes, sleep duration, and depression in adolescents to explore the potentially bidirectional relationship between short sleep duration and depression.

For this scope they analysed 15,659 US adolescents in grades 7 to 12. The results showed that adolescents with parental set bedtimes of midnight or later were 24% more likely to suffer from depression (OR = 1.24, 95% CI 1.04-1.49) and 20% more likely to have suicidal ideation (1.20, 1.01-1.41) than adolescents with parental set bedtimes of 10:00 PM or earlier, after controlling for covariates. Consistent with sleep duration and perception of getting enough sleep acting as mediators, the inclusion of these variables in the multivariate models appreciably attenuated the associations for depression (1.07, 0.88-1.30) and suicidal ideation (1.09, 0.92-1.29).

From Table 3

Odds ratios (95% CI) for depression

	Model 1a	Model 2b	Model 3c	Model 4d
Parental set bedtime on weekday nights
10:00 PM or earlier	1.00	1.00	1.00	1.00
By 11:00 PM	1.15 (0.94-1.40)	1.13 (0.90-1.42)	1.10 (0.87-1.39)	0.97 (0.76-1.24)
By or after midnight	1.42 (1.21-1.67)	1.28 (1.07-1.52)	1.24 (1.04-1.49)	1.07 (0.88-1.30)
Self-perception of how much parents care
1 – Not at all			6.82 (3.11-14.98)	5.88 (2.79-12.40)
2 – Very little			8.32 (4.58-15.12)	6.73 (3.49-12.98)
3 – Somewhat			5.50 (3.72-8.13)	4.93 (3.32-7.30)
4 – Quite a bit			2.43 (1.89-3.13)	2.16 (1.69-2.76)
5 – Very much			1.00	1.00
Adolescent-reported sleep duration
≤ 5 h				1.71 (1.22-2.39)
6 h				1.29 (0.97-1.70)
7 h				1.19 (0.96-1.48)
8 h				1.00
9 h				1.17 (0.88-1.56)
≥ 10 h				1.34 (0.95-1.89)
Enough Sleep				0.35 (0.28-0.43)

^aModel 1 – Unadjusted.

^bModel 2 – Adjusted for age, sex, race/ethnicity, parent's marital status, and family receipt of public assistance.

^cModel 3 – Adjusted for variables in Model 2 plus self perception of how much parents care.

^dModel 4 – Adjusted for variables in Model 3 plus adolescent reported sleep duration and perception of getting enough sleep.

From:

Sleep. 2010 January 1; 33(1): 97–106.

The results from this study provide new evidence to support the notion that short sleep duration could play a role in the etiology of depression. Earlier bedtimes could therefore be protective against adolescent depression and suicidal ideation by lengthening sleep duration.

Young athletes have to cope nowadays with various stresses, not only performance related. Studying, maintaining social contacts, training, family and peer pressure are all parts of young athlete’s  lives. Sleep is a simple thing that can make sure they recover properly and can cope with everything they have to deal with.

So, are we making sure they get good quality and good amounts of sleep?

Do we advice them on appropriate bed time?

Do we make sure they don’t spend the night playing videogames or chatting on social networks?

Do we create the right sleeping environment and routines?

Do we know if they are sleeping well?

How about a checklist?

Read Atul Gawande’s book about checklists, The Checklist Manifesto. Not only is the book loaded with fascinating stories, but it honestly changed the way I think about the world. The book’s main point is simple: no matter how expert you may be, well-designed check lists can improve outcomes. So, let’s make sure our young athletes tick all the boxes when it comes to sleep.

Sleep is good for you

Sunday is one of my favourite days as I tend to have time to do some reading. I like to read everything, but today i particularly enjoyed something recently published on sleep using an interesting animal model.

The benefits of sleep seem obvious. However, scientists have long debated precisely how it improves brain performance at the cellular level. One theory argues that sleep reduces the unimportant connections between neurons, preventing brain overload. Another theory maintains that sleep consolidates memories from the previous day.

I have previously discussed in this blog the importance of sleep for athletes with particular reference to the possibility of videogames altering the normal sleep-wake cycle.

Recent work published on Neuron shows how the circadian clock and sleep affect the scope of neuron-to-neuron connections in a particular region of the brain. The authors also identified a gene that appears to regulate the number of these connections.

The study was conduced studying the larvae of a common see-through aquarium pet, the zebrafish. Like humans, zebrafish are active during the day and sleep at night.

The researchers, led by Lior Appelbaum and Philippe Mourrain of Stanford University, tagged the larvae neurons with a dye (Synaptophysin,  pre-synaptic marker) so that active neuron connections, or synapses, appeared green, whereas inactive ones appeared black.

After following the fluctuations of these synapses over the course of a day, the team found that the zebrafish did indeed have lower overall synapse activity during sleep.

The scientist are pretty much of the impression that sleep is an active process that reduces the activity in the brain. This reduction in brain activity allows the brain to recover from past experiences.

Without the synapse reduction that happens during sleep the brain would not have the ability to continually take in and store new information. So the importance of sleep i an athletic population is not relevant only for physical recovery, but possibly to facilitate learning and memory all activities incredibly important in sports where tactical aspects are crucial.

More studies are needed but this particular study provides the first insights on NPTX2, a protein implicated in AMPA receptor clustering which modulates circadian synaptic changes. Overexpression of NPTX2b in hypocretin/orexin (HCRT) neurons induces melatonin resistance, so for sure there is a need for more studies in this field to understand the links between sleep and brain function.

New recommendations for dietary intake of Vitamin D and Calcium

Most Americans and Canadians up to age 70 need no more than 600 international units (IUs) of vitamin D per day to maintain health, and those 71 and older may need as much as 800 IUs, says a new report from the Institute of Medicine. The amount of calcium needed ranges, based on age, from 700 to 1,300 milligrams per day, according to the report, which updates the nutritional reference values known as Dietary Reference Intakes (DRIs) for these interrelated nutrients.

The report's recommendations take into account nearly 1,000 published studies. A large amount of evidence, which formed the basis of the new intake values, confirms the roles of calcium and vitamin D in promoting skeletal growth and maintenance and the amounts needed to avoid poor bone health. The current evidence in fact seems to suggest the need for increasing Vitamin D levels not only in the elderly, but also in athletic populations. In fact, young athletes and dancers have been recently identified to present vitamin D insufficiency, despite the fact they live in a sunny country, suggesting that screening and increase Vitamin D intake is necessary to avoid health problems.

The committee that wrote the report also reviewed hundreds of studies and reports on other possible health effects of vitamin D. While these studies point to possibilities that suggest potential benefits of Vitamin D supplementation, they have yielded conflicting and mixed results. Rigorous trials that yield consistent results are vital for reaching conclusions, as past experiences have shown. Vitamin E, for example, was believed to protect against heart disease before further studies disproved it.

Adequate Vitamin D levels seem to be important in athletes (in particular female athletes) as a serum 25(OH)D concentration of >or=32 and preferably >or=40 ng.mL(-1) can reduce the risk for conditions such as stress fracture, total body inflammation, infectious illness, and impaired muscle function.

A part from supplementation, outdoor training time (during peak sunlight) is important and can influence Vitamin D levels.

Something else to think about, in particular in athletes training and competing indoor and in athletes leaving in “dark” countries.