16/3/2017 0 Comments
The importance of hydration
Water plays an important role in exercise, especially for thermoregulation. Inadequate hydration or dehydration not only affects performance, but also causes serious health complication or even death, if not managed properly. In Singapore’s hot and humid weather, the risk of dehydration through sweat loss during exercise is even more significant. Fluid loss of 3%-5% of body weight results in cardiovascular strain and impaired function to dissipate heat. Collapse is likely at 7% loss. 
Here are several tips on combating dehydration during exercise
The guidelines for proper hydration are shown below 
 Greenleaf, J. E., & Harrison, M. H. (1986). Water and electrolytes.
 Sports Singapore (2017, March 16). Safety Resources & Useful Links. Heat Disorders Prevention Guide. Retrieved from https://www.sportsingapore.gov.sg/sports education/sports-safety/safety-resources-and-useful-links
Strength and power athletes typically have to develop and maintain excessive body mass (especially lean mass) and also extreme strength and power. Thus, sound dietary practices are just as important as proper training practices. There are three components to consider in regard to the energy requirements of these athletes.
1. Daily energy requirement
This is determined by three factors which are the basal metabolic rate (BMR), physical activity and the thermic effect of food. According to Wilmore and Costil (2001) as cited in Antonio (2008), of these three factors, BMR accounts for about 60-70% of the total daily calories. This is followed by physical activity which is the most variable factor. The least significant factor is thermic effect of food which refers to the amount of calories required to digest and absorb the consumed foods.
The Harris-Benedict equations (Harris and Benedict, 1919 as cited in Antonio, 2008) are most frequently used to calculate BMR or more practically, resting metabolic rate (RMR) instead.
Males: BMR (calories/day) = 66.5 + (13.75 x weight in kg) + (5.003 x height in cm) – (6.775 x age in years)
Females: BMR (calories/day) = 655.1 + (9.5663 x weight in kg) + (1.85 x height in cm) – (4.676 x age in years)
This will provide us with the minimum amount of daily calories required by a person at rest. However, we need to also consider their daily physical activity level (PAL) to calculate their daily energy expenditure and thus their minimum daily calorie requirement. We have to multiply the RMR by a PAL factor that best resembles them. Table 1 below shows the various PAL factors.
Table 1: Physical activity level factors
Example: I am 170 cm in height and 62 kg in weight. I would consider myself to be active. Thus my PAL factor is 1.76.
Calculations: BMR (calories/day) = 66.5 + (13.75 x 62) + (5.003 x 170) – (6.775 x 32)
= 1553 calories/day
Minimal daily calories requirement = 1553 x 1.76
= 2733 calories
2. Body weight goals
If the athlete needs to increase or decrease body mass, we need to adjust the daily calorie intake to be above or below the minimal daily calories requirement. One pound of body fat is about 3500 calories. For weight/fat loss, the athlete should ingest 500 calories lesser daily which would allow him/her to lose one pound of fat per week.
One pound of muscle is about 2500 calories. So for muscle gains, the athlete should ingest about 300-500 calories more daily. It is recommended that the athlete eat about 4-6 meals per day in order to meet this required intake.
3. Macronutrient needs
Once these two factors are addressed, we need to consider the issue of macronutrient intake. Most strength/power athletes should get 12-15% of their calories from protein, 55-60% from carbohydrates and 30% from fats (<10% from saturated fats) (Kreider and Almada, 2004 as cited in Antonio, 2008)
Antonio, J., Kalman, D., Stout, J. R., Greenwood, M., Willoughby, D. S., & Haff, G. G. (Eds.). (2008). Nutritional needs of strength/power athletes. In A. Stopppani, J, Scheett, T.P. and Mcguigan, M.R. (Eds.), Essentials of sports nutrition and supplements (pp. 350-352). Chapter Humana Press.
Harris, J. S., & Benedict, F. G. (1919). A Biometric Study of Basal Metabolism in Man (Carnegie Institution of Washington publication# 279). Washington, DC: Carnegie Institute.
Kreider, R. B., Almada, A. L., Antonio, J., Broeder, C., Earnest, C., Greenwood, M., & Ziegenfuss, T. N. (2004). ISSN exercise & sport nutrition review: research & recommendations. Sports Nutr Rev J, 1(1), 1-44.
Wilmore JH, Costill DL. Metabolism, energy, and the basic energy systems. In: Physiology of Sport and Exercise. 3rd ed. Champaign, IL: Human Kinetics Publishers; 2001: 139
For the endurance athletes, their performances are heavily dependent on having adequate supply of carbohydrate. Our body has a limited supply of carbohydrate compared to the amount of fat and protein. About 300-500 g of glycogen is stored in the muscles and another 75-100 g is stored in the liver (Bjorkman and Wahren, 1988). However, this amount is sufficient for us to run at moderate intensity for 20 miles (32 km)! An increase in exercise intensity will lead to an exponential increase in this utilization rate with the major contribution from muscle glycogen (Saltin and Karlsson, 1971).
It is not necessary for endurance athletes such as runners to engage in special dietary strategies such as carbohydrate loading during practices and races especially if the intensity is not high and the distance is relatively short.
Bjorkman, O., & Wahren, J. (1988). Glucose homeostasis during and after exercise. RL Terjung. New York: Macmillan, 100-115.
Saltin, B., & Karlsson, J. (1971). Muscle glycogen utilization during work of different intensities. In Muscle metabolism during exercise (pp. 289-299). Springer US.
It is common for endurance athletes to engage in glycogen loading or carbohydrate loading as it is more commonly called. They believe that this coupled with a modified training programme will maximize glycogen stores and lead to improved performance. Some researchers such as Hawley et al. (1997) as cited in Antonio (2008) suggested that glycogen loading of supercompensation can be beneficial for endurance bouts that last longer than 90 minutes. It is reported by Hawley et al. (1997) that glycogen loading can reduce fatigue during endurance training and increase duration of exercise bout by 20% while increasing workload or distance completed by 2-3%.
Accordingly to Antonio (2008), the classic carbohydrate loading method requires a 3-4 day glycogen-depleting regime which contained hard exercise coupled with a low carbohydrate diet followed by a 3-4 day repletion phase in which training volume and intensity were decreased whereas carbohydrate consumption was significantly increased. The drawback of this method is that workout quality suffered during the depletion phase and optimal performance was not achieved.
Sherman et al. (1981) as cited in Antonio (2008) proposed an alternative method. It required the athlete to consume a 50% carbohydrate diet for 3 days while slowly reducing training volume. The athlete will consume 70% carbohydrate diet from the fourth day while still reducing training volume. On the seventh day, the athlete will compete. The authors reported that this modified method is highly effective for loading glycogen with less risk of performance decrements than the classic method.
Antonio, J., Kalman, D., Stout, J. R., Greenwood, M., Willoughby, D. S., & Haff, G. G. (Eds.). (2008). Carbohydrates. In A. Haff, G.G (Eds.), Essentials of sports nutrition and supplements (pp. 301). Chapter Humana Press.
Hawley, J. A., Schabort, E. J., Noakes, T. D., & Dennis, S. C. (1997). Carbohydrate-loading and exercise performance. An update. Sports medicine (Auckland, NZ), 24(2), 73.
Sherman, W. M., Costill, D. L., Fink, W. J., & Miller, J. M. (1981). Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance. International Journal of Sports Medicine, 2(2), 114.
2/11/2013 0 Comments
Recommended protein intakes
It has been argued that physically active individuals need more protein than is currently recommended. Antonio (2008), p.255-256 gave some guideline for the recommended daily allowance (RDA) (grams of protein/kg body weight/day) for protein for sedentary adults as well as physically active individuals.
Sedentary (adult) – 0.8
Recreational exerciser (adult) – 1.0-1.4
Resistance-trained (maintenance) – 1.2-1.4
Resistance-trained (gain muscle mass) – 1.4-1.8
Endurance-trained – 1.2-1.4
Intermittent, high intensity training – 1.2-1.8
Weight-restricted sports – 1.4-2.0
Adapted from Williams (2005) and other sources as cited in Antonio (2008)
Antonio, J., Kalman, D., Stout, J. R., Greenwood, M., Willoughby, D. S., & Haff, G. G. (Eds.). (2008). Protein. In A. Ziegenfuss,T.N. and Landis, J. (Eds.), Essentials of sports nutrition and supplements (pp. 255-256). Chapter Humana Press.
Williams MH. Nutrition for Health, Fitness, and Sport. 7th ed. New York: McGraw-Hill; 2005
Skeletal muscle is approximately 72% water, 22% protein, and 6% fat, glycogen, and minerals. One pound (~ 0.45g) of muscle tissue contains ~ 100g of protein. In order to gain 1 lb of lean mass per week, an athlete would have to ingest an extra 14g of protein per day (100g/7 days). This calculation seems easy but in practice, it is not that simple. Most experts believe that the single most important factor in gaining lean mass (along with resistance training) is to consume a hyperenergetic or excess calories diet. The individual should consume an additional 200-400 kcal/day (3-5kcal/kg/day) above maintenance requirements in addition to consuming the extra protein intakes as recommended.
Antonio, J., Kalman, D., Stout, J. R., Greenwood, M., Willoughby, D. S., & Haff, G. G. (Eds.). (2008). Protein. In A. Ziegenfuss,T.N. and Landis, J. (Eds.), Essentials of sports nutrition and supplements (pp. 259). Chapter Humana Press.
All information presented on this site is meant for general purposes. It is not meant to replace health and medical advice from healthcare professionals.
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