Friday, January 24, 2014

How to combat the negative effects of hyperthermia on cognitive function?

Although cognitive performance improves with mild heat strain, an impairements might be observed at high levels of hyperthermia (gastrointestinal temperature above 39 oC, Racinais et al., 2008). Neck cooling has been shown to improve enduarnce performance in previous studies but very limited information exists on the effect of this method on cognitive function.

The study by Lee and colleagues, published this week in the European Journal of Applied Physiology, examined the effect of neck cooling on cognitive performance during prologed exercise in the heat. A neck-cooling collar was placed on the neck of individuals who run for 75min or until exhaustion in an environmental chamber which mantained dry bulb temperature of 30 oC and 70% relative humidity.

The main finding was that neck cooling may enhance performance in high complexity tasks. It is important to note that this beneficial effect was observed while the neck-cooling collar was kept at the neck for the enitre period of exercise. Although this method of cooling could be applied in some endurance events, certain questions need to be answered before using it in team sports. For instance, what is the effect of neck cooling when applied just before the start of the match an/or in half-time?

For further reading
Lee et al. Neck cooling and cognitive performance following exercise-induced hyperthermia. Eur J Appl Physiol 2014;114: 375-384
Racinais et al. Hyperthermia impairs short-term memory and peripheral motor drive transmission. J Physiol 2008;586: 4751-4762

Friday, January 3, 2014

Do muscles "remember"? Implications for training

The term "muscle memory" has been used to describe the observation that muscle function related tasks seem to be performed more effectively after a period of detraining in previously trained muscle groups compared with the control ones. Additional evidence on this phenomenon has been published on October 28th 2013 by Egner, Bruusgaard and colleagues in the Journal of Physiology.

What they did?
  •  Mice were treated with testosterone for 14 days. This treatment resulted in 66% increase in the number of myonuclei and 77% increase in fibre cross-sectional area.
  • Fibre size was decreased within 3 weeks of treatment removal. However, myonuclei number remained elevated for at least 3 months post-treatment. 
  • At the end of the 3 month post-treatment period, exercise that lasted 6 days increased cross-sectional area by 31% in the group with elevated myonuclei without any change in the control group.

Potential practical applications
Based on these findings, the authors speculated that muscles might "remember". It can be assumed that previously trained muscles/individuals might improve at a faster rate when they resume training after a period of detraining compared with the control ones. "Muscle memory" could also explain, at least in part, why some individuals improve more with training than others.

Future challenges
Does strength training early in sports life, which results in extra nuclei, maximize the athletic potential?

Egner, Bruusgaard, Eftestol and Gundersen (2013). A cellular memore mechanism aids overload hypertrophy in muscle long after an episodic exposure to anabolic steroids. Journal of Physiology DOI: 10.1113/physiol.2013.264457