Strenua's World» Drink

Can Caffeine Improve Competitive Performance?

Strenua — Fri, 10 Jul 2009 15:09:27 +0000

This weekend sees the first of the long training runs for this November’s New York City Marathon. These long training runs are good opportunities to test new race strategies ranging from what to eat for breakfast before the race, discovering if you can tolerate NSAID’s with exercise, or finding which energy gels or drinks you can stomach best. This weekend I’m going to be introducing caffeine into my pre run diet. Since 2004, caffeine is no longer banned by the World Anti Doping Agency, and many sports products have started to include it.

Sporting Benefits of Caffeine

Consuming moderate amounts of caffeine (3-6mg/kg Body Mass), 60 minutes prior to exercise has been shown to enhance performance during prolonged, sub maximal exercise, and during short bursts of high intensity exercise. It has been consistently shown to reduce an athlete’s rating of perceived exertion and the reporting that exercise feels easier.

Caffeine can stimulate the Central Nervous System and reduce the perception of effort so you feel better and can increase push yourself harder or for longer. In both time trials, and exercise to exhaustion tests, caffeine has been shown to improve performance and delay the onset of fatigue, but benefits varies between individuals, another reason you should try before using caffeine in a competition.

Caffeine has also been shown to improve an athlete’s ability to maintain performance during repeated bouts of high intensity activity, by improving mental processing important to sport alertness, concentration, reaction time, focus. Improvements have been seen with concentrations of just 1-2 mg/kg Body Mass.

Caffeine Side Effects

Caffeine has been reported to produce minimal adverse effects, but include insomnia, headaches, dizziness, flushing, tachycardia (rapid heart rate), trembling and gastrointestinal distress. Whilst these symptoms are caused by the effect of caffeine on the Central Nervous System, they are individual in nature which is why trying caffeine should be trialed in training prior to use in competition especially if you aren’t used to consuming caffeine on a regular basis.

When ingested in high doses (greater than 500 mg per day) for use in sport, caffeine can have side effects. Consuming too much caffeine may reduce the performance benefit due to reducing your sensitivity to caffeine. As a result, caffeine is best used as a performance aid in competition, and not regularly in training except in the right circumstances such as a tough training session.

Whilst caffeine is a known diuretic, (generally at doses exceeding 9mg/kg Body Mass), if it is consumed just before or during exercise it doesn’t affect known markers of hydration. In moderation caffeine also has no effect on thermoregulation during exercise.

How Much Caffeine Should You Consume?

3-13mg/kg Body Mass caffeine is suggested to improve endurance performance. For someone weighing 60kg this is around 180-780mg, although unless you normally consume a lot in your diet, there isn’t much benefit reported with more than 3mg/kg.

Caffeine is found already in many foods and drinks so you may not need to supplement your diet that much, although here are some common caffeine sources:

40-100mg in cup of instant coffee
60-150mg in brewed coffee
40-50 mg in 12oz cola drink
100mg in 2 tablets of caffeine tablets such as Pro Plus
80mg in 250ml can of Red Bull
80mg in 500ml of Lucozade Sport with caffeine

It is recommended to consume caffeine 1 hour prior to exercise to allow the caffeine to peak in the blood stream. However, caffeine is likely to start to exert an effect within 15 minutes and therefore consuming a caffeine drink or supplement at the start of exercise could still have a beneficial effect as long as the duration of exercise is longer than 45 minutes.

Cereal and non-fat milk support muscle recovery after endurance exercise

Strenua — Tue, 09 Jun 2009 22:28:38 +0000

It’s something I know I’m guilty of. Come back from a long run, get in the bath and forget all about eating and refuelling.

Endurance exercise affects skeletal muscle by reducing energy stores and increasing muscle protein breakdown. So after exercise it’s important to refuel and replace the bodies main source of stored energy, glycogen. During endurance exercise glycogen stored in skeletal muscle is reduced which can limit exercise duration and intensity. Therefore, it is important to replenishing these energy stores before your next training session or competition.

In addition, muscle protein breakdown is continuously occurring, even at rest, releasing amino acids to be used for protein synthesis. However, protein synthesis is stimulated by exercise and muscle protein breakdown is increased. So it’s important that consumption of food must offset breakdown to create a positive net muscle protein balance.

Taking these two facts into account suggests that the ideal recovery food must contain both carbohydrate and protein to provide substrate for glycogen synthesis and achieve net protein balance. But what’s the best fuel to use?

Commercial carbohydrate-electrolyte sports drinks are available for post exercise recovery, but how do they compare with eating regular food. A group of researchers from the University Texas have compared the effects of ingesting regular cereal and non-fat milk, with drinking carbohydrate-electrolyte sports drink immediately following endurance exercise, investigating muscle glycogen synthesis and the regulation of proteins controlling protein synthesis.

Whilst many studies use untrained subjects or exercise to exhaustion Dr Kammer’s study a more realistic training scenario. The study published in Journal of the International Society of Sports Nutrition involved trained cyclists and triathletes who completed 2 hours of cycling at 60-65% of their predetermined VO₂MAX (this is the maximum volume of oxygen that can be used during one minute of maximal exhaustive exercise).

Immediately after exercise the subjects consumed either a drink (containing 78.5 g carbohydrate) or cereal (77 g carbohydrate, 19.5 g protein and 2.7 g fat). The researchers found that after 60 min following refuelling with either the drink or cereal:

blood glucose levels was similar between both drink and cereal;
significant changes did occur in glycogen levels following both methods of refuelling;
glycogen and muscle proteins were not different between treatments.

BUT

after cereal blood insulin levels was significantly higher;
after cereal blood lactate was significantly lower;
only cereal significantly affected glycogen synthase.

The researchers were able to conclude that while the drink provided carbohydrate, only the cereal and milk provided carbohydrate and essential amino acids necessary to support both glycogen and protein synthesis. This is due to the cereal option also providing easily digestible and quality protein in the milk. The benefits of the findings to the everyday athlete is that cereal and non-fat milk provide a less expensive whole food option as compared to sports drinks.

Whilst Dr Kammer and colleagues now suggest cereal and non-fat milk as a potential option for athletes who refuel at home, the down side was that to eat the necessary amounts of carbohydrates required consuming the equivalent of two potions according to the recommended sizes on the box.

So now we know what to eat, I just need to schedule time for it straight after training, before I head for the bath.

Chill as you rehydrate to improve endurance

Strenua — Tue, 02 Jun 2009 11:15:44 +0000

With summer arriving and temperatures rising, it’s even more important than ever that you take out your drinks bottles when you are training or competing.

We all are aware that dehydration through sweating can compromise athletic performance. Evaporating sweat from the skin surface is the body’s way of regulating our core body temperature, essential whilst exercising in this summer heat. Unfortunately if our sweat loss exceeds fluid intake we can become dehydrated, this is increased if you are involved in intense exercise, in a hot, humid environment. Dehydration of just 1-2% of body weight begins to compromise physiological function and negatively influence performance. However you should drink according to individual needs and not on published recommendations as hyperhydration can be as dangerous as dehydration. I shall write more about how to determine your own personal fluid intake in a later article.

You probably have your own personal favourite drink when training or competing, whether it’s a manufactured sports drink, your home made recipe, or just plain water. But have you considered the effect the temperature of the drink may have on your performance?

In the journal Medicine & Science in Sports & Exercise,researchers from Loughborough University investigated the effect of drink temperature on cycling capacity in the heat. The two groups of males cycled to exhaustion in hot (35^oC) and humid (60%) environments. The subjects drank three 300-mL volumes of either a cold (4^oC) or a warm (37^oC) drink during 30 mins of seated rest before exercise and 100 mL of the same drink every 10 mins during exercise.

They found that compared to the warm drink, drinking cold drink resulted in:

Longer exercise time – (64mins with cold 52 mins with warm).
Lower mean skin temperature after 20 mins during exercise.
Lower heart rate before exercise and for the first 35 min of exercise.
Reduced sweat rate (1.22 L/hr for the cold and 1.40 L/ hr with the warm drink).
Lower perceived exertion during exercise.
There was no effect of drink temperature on mean skin temperature at rest.
Overall improved endurance capacity of around 23%.

Author of the paper, Dr Jason Lee, concluded that compared with a drink at 37^oC, the ingestion of a cold drink before and during exercise in the heat reduces physiological strain during exercise due to reduced heat accumulation.

Obviously keeping your drink at 4^oC isn’t practical if you have to carry it as you run or cycle, but how about keeping your drink in the fridge before you start exercising. During exercise you can make sure it’s kept in the shade or a bucket of iced water, if you are playing sport in a fixed location. I also like to put my drink in the freezer before I go out. Not enough for the drink to freeze solid but enough to allow a few ice crystals to form to keep it chilled for longer. If I can make my endurance capacity increase by 23% just through the temperature of my drink, I think this is one suggestion I’m going to try to incorporate in my running this summer.

Do you have any suggestions how to keep you drink colder, for longer whilst exercising during the summer? If so let us know.