The main causes of athletic fatigue are carbohydrate depletion and dehydration

Second Half Slump

The main causes of athletic fatigue are carbohydrate depletion and dehydration.

CARBOHYDRATES: Glycogen is carbohydrate fuel stored in the muscles and liver; carbohydrate is the fuel of choice for high intensity exercise. The alternating fast and slow running in soccer can easily deplete glycogen stores. Studies show that many elite soccer players eat only ~300 grams (1,200 kcal) of carbohydrate per day, far below the optimal level of 500-750 grams (2,000-3,000 kcal) of carbohydrate required. As a result, many soccer players start their competitions with low glycogen levels. Players who start a match with low glycogen levels usually have little carbohydrate left in their muscles by the time the second half starts resulting in poor second half performances:
• Glycogen depleted soccer players usually run more slowly – sometimes by as much as 50% - during the second half of matches compared to the first.
• Glycogen depleted players spend more time walking and less time sprinting.
• Total distance covered during the second half is often reduced by 25% or more in players with low glycogen levels, indicating that overall quality of play deteriorates as glycogen levels go down.
• In one study that compared the impact of using a sports drink versus water during 10 matches found in the games when they used sports drink, the team allowed fewer goals and scored significantly more times, especially in the second half. When they only drank water, the players were less active and reduced their contacts with the ball by 20-50% during the final 30 minutes of the game
• Another study showed that consuming a sports drink immediately before and at the halfway mark of a soccer match simulation improved dribbling, agility and shooting performance in elite soccer players.

HYDRATION: Athletes typically drink only HALF of what they need. This is true for soccer players! Sweat losses of 4-10 cups per 90 minute game in cool conditions and approximately 17 cups during hot conditions have been reported in studies on elite soccer players:

Session Season Men
Sweat Losses-(ml/hr) Men
Fluid Intake
(ml/hr) Women
Sweat Losses
(ml/hr) Women
Fluid Intake
(ml/hr)
Practice Summer 985 ± 320 429 ± 312 814 ± 244 395 ± 154
Winter 746 ± 259 311 ± 257 - -
Game Summer 1209 ± 330 516 ± 337 761 ± 220 408 ± 154
Winter 1027 ± 267 361 ± 195 - -

ACTION STEPS:
1. Increase daily carbohydrate intake to 3.6-4.5 grams per pound body weight per day. A 150 lb player would require 540-675 g CHO/day; a 175 lb player would require 630-788 g CHO per day.
2. Eat a high carbohydrate meal 3-4 hours before competition with~150 grams carbohydrate. Example: 2 cups pasta + ½ cup marinara + 8 oz. milk OR Turkey sandwich + large piece of fruit and water to drink.
3. Consume carbohydrate DURING competition with 30 g CHO 10-15 minutes before competition and again at half time. Practice using different carbohydrate sources at practice to see what you tolerate best (16 fl. oz. Gatorade Thirst Quencher = 28 g CHO)
4. Hydrate!
o Athletes require 10-12 cups (80-96 oz.) of fluid per day PLUS fluid ~2 cups before, 4-8 oz. every 15-20 minutes during and ~ 3 cups after exercise.
o To know if you are drinking enough, check your weight before and after exercise several times per year. Your goal is to limit weight loss through dehydration to no more than 2% of your body weight (Example: A 150 lb athlete should lose no more than 3 lbs during exercise). Drink 24 oz. fluid for every pound lost during exercise.
o Monitor your urine color: Aim for a pale to light colored urine throughout the day and to need to void your bladder at least 3 times prior to an afternoon workout.
o If you’re a salty sweater or prone to cramping, replace electrolytes (sodium & potassium) by drinking a sports drink and eating salty foods (pretzels, pickles, pasta sauce, soup) and/or salting your food.
o Drink on a schedule - not just when you’re thirsty.
o Eat more fruits & veggies – they’re high in water content.