Examples of fluids used by Sports nutrition in London

Sports nutrition in London – dehydration can have a serious negative effect on performance.

As little as 2% dehydration causes:

• 8% loss of speed
• 10% loss of strength
• 20% loss of cognitive function

Dehydration occurs through the loss of water from the body, mainly in the form of sweat that is evaporated from the skin as the body tries to prevent overheating. Sweat volume and electrolyte loss varies from individual to individual and depending on the ambient temperature. Some individuals can produce large volumes of sweat during exercise but may be very good at retaining electrolytes preventing camps and decreased performance, while others may be “salty sweaters” and lose large amounts of electrolytes leading to cramping and decreased performance.

Monitoring hydration status, sweat volume and electrolyte loss is an important job for Steve Hines sports nutrition in London; clearly both examples previously mentioned would require different strategies to maintain hydration and performance.

Sports nutrition in London and monitoring hydration status

There are different ways of monitoring hydration levels employed by Steve Hines sports nutrition in London before, during and after exercise including:

Urine testing

• Urine colour – basing your urine colour against a chart of different colours has been used for some time to determine hydration status. A dark yellow / brownish colour indicates dehydration, whereas a clear light yellow colour indicates hydration. This form of hydration assessment can be quite inaccurate, for example if you take a multivitamin your urine will be bright yellow regardless of whether you are hydrated or not.
• Specific gravity (SG) measures the concentration of particles in the urine; the normal range is considered 1.020-1.030g/ml. A high specific gravity (i.e. above 1.030, thus more concentrated particles in the urine) indicates dehydration. A urine sample can be collected and measured with a SG device or pee sticks.
• Osmo check measures refractive index, which is directly correlated to specific gravity and indirectly related to osmolality of the urine you pass (a high osmolality value means the urine is more concentrated and the body is dehydrated, whereas a low osmolality means the urine is less concentrated and the body is hydrated). Values of 400 mOsmols/kg H2O or below generally indicate hydration, values of 400-800 mOsmols/kg H2O indicate dehydration and values above 800 mOsmols/kg H2O indicate severe dehydration. A urine sample can be collected and measured with an osmo check device.

Sports nutrition in London and measuring sweat volume loss

Stofan et al (2003) demonstrated that gross sweat loss were slightly greater for American football players who suffered cramp (4 litres over a 2 and a half hour session) compared to those who did not suffer cramp (3.5 litres over a 2 and a half hour session) and demonstrates that actual fluid loss seems to play some role in dehydration, cramp and decreased performance.

Sweat loss during exercise has been reported in a variety of other sports and ambient temperatures. In elite footballers at an ambient temperature of 6-8 degrees C averaged sweat lost was 1.68 litres over 90 minutes and at an ambient temperature of 24-29 degrees C it was 2.03 litres. (Maughan et al 2007, 2004). Average sweat losses of 2.6 litres per hour have been reported at an average temperature of 31 degrees C in tennis players (Bergeron 2003), and 1.8 litres per hour at an average temperature of 14 degrees C in ice hockey players (Palmer and Spriet 2008). There were quite large variations in total sweat losses between individuals and across the different sports, generally with more sweat volume lost as the ambient temperature increased.

Sweat rate is usually calculating by recording before and after training body weight whilst considering fluid intake and urine passed:

Sweat rate = (pre training weight – post training weight) + fluid intake – urine passed / time of the session.

General advice is to consume 1.5 litres of fluid for every kg of body weight lost and is quite a simple strategy for elite and amateur athletes to employ to maintain hydration.

Sports nutrition in London and measuring electrolyte loss

Electrolytes lost in sweat include sodium (Na), chloride (Cl), potassium (K) and magnesium (Mg). Electrolyte loss is believed to contribute to cramping and fatigue due to the following mechanisms:

• Loss of muscle Mg – Mg is required for the myosin head to detach from actin, and a loss of Mg can cause a “permanent contraction” experienced during cramping.
• Loss of Na and K affects the Na / K pump in nerve and muscle tissue affecting nerve condition leading to neural fatigue.

Patches can be applied to the skin such as the chest and back, absorbing sweat that can be analysed for sweat electrolyte concentrations. A lot of research has measured Na loss in sweat; values have been reported at 15-66mmol/L (Shirreffs et al, 2005) and 33-79mmol/L (Maughan et al, 2007) in footballers, 23-83mmol/L in tennis players (Bergeron, 2003) and 27-88mmol/L in ice hockey players. There is less data on other minerals lost in sweat such as K, Cl and Mg, but K losses can be 3.7-8.5 mmol/L (Maughan et al, 2007), and 2.96-4.5mmol/L in football (Shirreff’s et al 2005) and mean Cl losses of 43mmol/L have been reported in footballers (Maughan et al, 2004). Mg losses in sweat may be negligible.

Stofan et al (2003) reported sweat K losses were similar between American footballer players who experienced cramp or who did not experience cramp, but sweat Na was significantly greater in those that experienced camp compared to those who did not (55mmol/L v 25mmol/L). Thus it would appear that Na lost in sweat plays the major role in dehydration, cramp and decreased performance.

It’s also clear to see there is quite a large difference in total “salt” losses between individual athletes. Some athletes are “salty sweaters” and suffer from heat cramping and severe decreases in performance whereas others may only lose small amounts of salt. Research has found that 1 in 20 white adults are heterozygous for the CF gene and can have 3-5 times the normal salt concentration in their sweat (Eichner, 2008). Clearly these individuals would need advice to salt their food and consume sports and other beverages with added electrolyte content.

These Na losses can equate to between 2.4-5.3g and research has also shown that during training athletes are not replacing sufficient amounts of Na and also possibly not enough Cl, K and Mg leaving themselves under recovered and at risk of poor subsequent performance (Palmer and Spriet, 2008).

Sports nutrition in London rehydration strategies

Drinking water is usually the first line strategy to replace fluids lost through sweat, however consuming large amounts of plain water is not recommended to replace fluid or electrolyte losses and can lead to hyponatremia and even death. Consuming beverages that contain electrolytes is the most senisble way to replace salt and water lost in sweat. These include sports drinks such as lucozade hydro, which contains 185mg of Na per 500ml. However, it would take between 13-28 500ml litre bottles of lucozade hydro to replace the amounts of Na that can be lost during training and games, which is obviously not a good idea. Drinking between 2 and 4 bottles of s sports drink such as Lucozade hydro may be appropriate during activity. Lucozade also produce a product called hydro plus powder sachets that contains 91mg per 100ml of fluid consumed which may be more appropriate to use if you regularly experience cramp or it is a particularly hot day. Beyond this and depending on the length of time and ambient temperature you train at, it may be wise to salt your food, however if you consume any processed foods you will need to take in to account the amount of salt in these products.

Another good option is to use the product Elete which provides 45mg of Mg, 390mg of Cl, 130mg of K and 125mg of Na per litre of water, this can be added to water, juice, tea and other beverages that you consume throughout the day to improve rehydration. More simply you could just add a pinch of good quality salt such as Celtic Sea Salt to your beverages – this is less scientific but a good option for those who do not want to spend money of pre-designed products. Other naturally “salty” drinks such as Vita Coco contain 40mg of Na, 66mg of calcium, 40mg of Mg and a whopping 740mg K. It also contains 16.5g of carbohydrates and 148mg of vitamin C and is a great alternative to a sports drink and could be consumed pre, during and after training and games.

Sports nutrition in London assessing your hydration status

To replace fluid loss after activity the easiest thing you can do to assess your hydration status is to record your pre and post training weight, adjust this for fluid consumed and urine passed and drink 1.5 litres of fluid for every kg of body weight lost. Once again these beverages should contain electrolytes and can be consumed gradually after activity.

For those more serious athletes or people who suffer from cramp it may be worth investing in a device that can measure urine osmolality or specific gravity, these devices cost approximately £300-400 and this way you can monitor your hydration on a daily basis. The use of sweat patches are not commercially available, however may be available if you work with a sport scientist or performance nutritionist and this can establish exact electrolyte loss from which a tailored rehydration and recovery protocol can be established such as whether you need to salt your food and / or consume certain amounts of sports drinks.

Sports nutrition in London References

Bergeron, M. F. (2003). Heat cramps: fluid and electrolyte challenges during tennis in the heat. Journal of Science and Medicine in Sport, 6 (1): 19 – 27.

Eichner, E. R. (2008). Genetic and other determinants of sweat sodium. Current Sports Medicine Reports, 7 (4): S36 – S40.

Maughan RJ, Merson SJ, Broad NP, Shirreffs SM. (2004). Fluid and electrolyte intake and loss in elite soccer players during training. International Journal of Sport Nutrition and Exercise Metabolism. 14 (3): 333 – 346.

Maughan, R. J. Watson, P. Evans, G. H. Broad, N. Shirreffs, S. M. (2007). Water balance and salt losses in competitive football. International Journal of Sport Nutrition and Exercise Metabolism, 17 (6): 583 – 594.

Palmer, M. S. Spriet, L. L. (2008). Sweat rate, salt loss, and fluid intake during an intense on-ice practice in elite Canadian male junior hockey players. Applied Physiology Nutrition and Metabolism, 33 (2): 263 – 271.

Shirreffs, S. M. Aragon-Vargas, L. F. Chamorro, M. Maughan, R. J. Serratosa, L. Zachwieja, J. J. ( 2005). The sweating response of elite professional soccer players to training in the heat. International Journal of Sports Medicine, 26: 90 – 95.

Stofan, J. R. Zachwieja, J. J. Horswill, C. A. Lacambra, M. Murray, R. Eichner, E. R. Anderson, S. (2003). Sweat and Sodium Losses in Ncaa Division I Football Players With A History of Whole-Body Muscle Cramping. Medicine and Science in Sports and Exercise: 35 (5): S48.

Sports nutrition in London – hydration strategies for elite performance.