Tag Archives: human physiology

Live High Train Low

Altitude has well established benefits for an athlete. Increased red blood cell production through increased erythropoietin (EPO) levels, results in a better ability of the blood to carry and deliver oxygen. Oxygen supply is one of the critical factors determining oxidative capacity and VO2max. At increasing altitude the partial pressure of oxygen decreases. This means that oxygen defusing from the lungs to the blood is reduced. Sensors in the body detect this reduction of oxygen dissolved in the blood. A series of physiological responses then act compensate. The magnitude and “shelf life” of these responses is dependant on the duration of exposure to a high altitude (hypoxic) environment. Most athletes therefore believe that the longer they stay at altitude the more beneficial it will be for them in terms of performance. A greater oxidative capacity is a major contributing factor in aerobic endurance and performance. While there is no doubt that altitude improves an athletes physiology and oxidative capacity, it may not always benefit athletic performance.

At altitude the poor supply of oxygen will make relative efforts more intense depending on the height above sea level. The higher an athlete goes the harder exercise at relative efforts will become. In some ways this is a benefit, as the athlete can improve both mentally and physiologically. With time it can also become a disadvantage. The athlete becomes accustomed to working at lower power outputs and pace in comparison to sea level. When they return to sea level they can struggle to maintain high pace even though they are physiologically capable. Technique and exercise efficiency can be greatly diminished by the time spent at altitude. For this reason an athlete will need to find a compromise between the physiological improvements and maintenance of technique. The live high, train low model is one such strategy which has shown success in overcoming this. An athlete will spend non training hours living in a hypoxic environment and will then return to sea level for training. They can also do this artificially by creating a hypoxic environment such as an “altitude house” or by sleeping in an “oxygen tent”. In either case the athlete is in an artificially controlled environment. They now can ensure sufficient duration in hypoxia to elicit a physiological response. They do not experience the issue with training intensity as they can complete their training at a sea level environment. When this method is adopted for a number of days or weeks the athlete can experience a significant overall improvement to aerobic performance. One exception to this theory is when an athlete is preparing for a competition that is at a high altitude venue. In this case the athlete must become acclimated to their competition environment. The loss in sea level performance is acceptable as the athlete must now focus his efforts around a performance in a new environment.

cat-430-walk-in-tent-system

Oxygen tent. Source http://www.snipview.com/q/Altitude%20tent

Depending on the goals and schedule of the athlete, altitude training can be a major benefit. Like with most training concepts there is a time and a place. Multiple factors must be considered in order to create an effective training strategy. We a constantly learning from science and real world experience. New technology such as oxygen tents can now allow us to make much better use of our knowledge of physiology and performance. Coaches and athletes should make a strong effort to stay informed about rapidly improving techniques.

Carbs and competition.

First off, I am not a dietician, nutritionist or even self proclaimed food guru. There are plenty of folk out there willing to preach about what you should and should not eat but that’s not my area. I am purely going to focus on the role of carbohydrate in sporting performance. Quite recently there has been large debate over carbohydrate in our diets. The “Health and Fitness revolution” has given rise to an enormous amount of conflicting information. People very easily fall for the latest fitness trends in search of the magic pill! The role of carbohydrate in human performance is pretty simple, it is fuel! Lately we have seen a large amount of athletes at the performance lab attempting to eat paleo. While I don’t have an issue with the paleo concept we have noticed that their diet, while rich in fruit and vegetables, is still generally quite low in carbohydrate as a nutrient. Paleo foods tend not to be very carb dense in comparison to other sources which they have now eliminated from their diet. As a result their performance tends to suffer somewhat. Dr. Loren Cordain one of the founders of the paleo diet concept also states this concern quite clearly in his work. We go to great lengths, explaining to athletes why carbohydrates are so important in their diet. That will be the focus of this post.

The Science

As most of you are aware the body uses three main energy systems. Glycolysis is the system which deals with carbohydrate as it uses glucose to generate ATP. At low intensity exercise the oxidative (Aerobic) system is most active. At increasing intensity larger motor units become active. These motor units tend to be glycolytic in nature (Anaerobic). These consume glucose which is sourced either from the bloodstream or stores known as glycogen. Once glucose and glycogen stores are depleted higher intensity cannot be maintained. This translates to a reduction in power output and speed. It is therefore important that an athlete has an adequate amount of glycogen stored prior to competition to maintain performance. Athletes will try to develop their oxidative system in an attempt to preserve glycolytic fuel stores. Fat stores contain more energy. The longer they can run on fat for energy the less glycogen they will use. The mistake people make is in thinking there is a distinct switch between fuels and energy systems. This is not the case. At all times all three systems are active but one will be more dominant. For this reason all systems must be considered in terms of diet and training. The nature of their sport will influence the nature of an athletes metabolism.

Game sports

rugby world cup 2011 NEW ZEALAND ARGENTINA

Image: rugby world cup 2011 NEW ZEALAND ARGENTINA by Jeanfrancois Beausejour

The level of intensity varies greatly in team sports. Depending on position there can be an extremely varied utilisation of one energy system or another. Glycolysis is however generally very active throughout game scenarios in team sports. Numerous studies have examined carbohydrate supplementation during a games. The supplementation groups showed a better maintenance of speeds and a greater distance covered in the later stages of a game than the non supplementation groups. In addition to this other studies have shown in soccer that better performing teams cover larger distances per game than poorer performing teams of the same league. It is pretty clear that carbohydrate is quite an important factor in performance.

Endurance sports

Photo Chris McCormack https://creativecommons.org/licenses/by-nd/2.0/

Photo Chris McCormack
https://creativecommons.org/licenses/by-nd/2.0/

Endurance sports are a little more interesting as the success of an endurance athlete is heavily related to fuel management and efficiency. A successful endurance athlete will dedicate a large amount of training time aimed at increasing oxidative capacity. This allows them to stay aerobic for longer essentially preserving glycogen. They aim to be as effective as possible at utilising fat metabolism. This will allow them to save glycogen for periods where they need to call on larger motor units. In short they try to use glycolysis only when they need to maintain a higher pace. The length of their event will determine the pace they wish to maintain and therefore the reliance on glycolysis and carbohydrate as a fuel source.

I will not mention individual foods or diets as I think that is mostly down to individual preference. The point I want to stress is that carbohydrate plays a very important role in performance for nearly all sports. It is important for an athlete to understand that role and not neglect it. They must choose a nutritional strategy that best suits the requirements of their given sport. At the end of the day their performance will reflect wether their diet is good for them or not!