~1.2 g of carbohydrate/kg body weight at 2-h inter-
vals up to 4 h (van Loon et al, 2000). The athlete
should also maintain a daily carbohydrate intake of
8–11 g/kg body weight per day to ensure optimal
muscle glycogen for repeated training bouts
(Burke, 1997; 2001).- Some research has indicated that consuming car-
bohydrate and protein following exercise increases
muscle glycogen synthesis rates more so than car-
bohydrate consumption alone (Ivy et al, 2002;
Zawadzki et al, 1992); however, other studies have
not confirmed this finding (Jentjens et al, 2001;
van Hall et al, 2000; Carrithers et al, 2000). - Adding protein to carbohydrate probably does not
increase muscle glycogen resynthesis but may stim-
ulate muscle protein synthesis. Data does indicate
that the optimal amount of carbohydrate required to
promote glycogen repletion is ~1.2 g/kg body
weight. The addition of protein to carbohydrate
may allow athletes to recover faster and perform
better during multiple training or competition bouts
and may help to repair damaged muscle fibers.
FLUID REPLACEMENT BEVERAGES
- During and after exercise of ~1-h duration, a fluid
replacement beverage containing 4–8% carbohydrate
(consisting of glucose, sucrose, glucose polymers,
fructose), sodium (10–20 mmol/L), and potassium
(3–5mmol/L) will provide both fluid and energy
(Convertino et al, 1996). - Fluid replacement beverages exhibit high rates of gas-
tric emptying compared to water and their taste facil-
itates increased consumption compared to water
(Tsintzas et al, 1995). - Urinary losses are less and fluid retention is greater
after training or exercise when consuming fluid
replacement beverages because of the increased drive
to drink owing to electrolyte content, particularly
sodium (Burke, 1997). - Some research suggests that even for intermittent,
high intensity, short duration type activities such as
sprinting, running, or jogging, there may be benefit in
use of fluid replacement beverages compared to water
(Sugiura and Kobayashi, 1998). - Carbonated beverages and fruit juices are not optimal
fluid replacement beverages because the carbohydrate
content is typically between 10 and 11%, too high to
ensure rapid fluid absorption, and the low electrolyte
content will not increase the drive to drink or maintain
fluid balance. In addition, carbonation will increase
the carbon dioxide content in the stomach and can
lead to gastric distress. Caffeinated products can
increase fluid loss, as well, but not all studies support
this view (Wemple et al, 1997).- Fructose as the sole carbohydrate source in fluid
replacement beverages should be avoided because
fructose absorption is considerably slower than glu-
cose and sucrose absorption which can contribute to
gastrointestinal distress (Murray et al, 1989). - The American College of Sports Medicine and the
National Athletic Trainers’ Association both recom-
mend drinking 400 to 600 mL (17–20 oz) of fluid 2–3 h
before exercise, another 7–10 oz, 10–20 min before
the event and then 150 to 350 mL (6–12 oz) every
15–20 min during exercise, beginning at the start of
the activity (Convertino et al, 1996).
•Following training or competition, it is necessary to
rehydrate with ~150% of fluid lost to completely
rehydrate (Burke, 1997).
ERGOGENIC AIDS- Ergogenic aids are products that have work-enhancing
effects (Burke and Read, 1993). Although many prod-
ucts are advertised as nutritional ergogenic aids, few
products are actually supported by research. Many
purported ergogenic aids provide no benefit (but are
harmless, e.g., coenzyme Q 10 , pyruvate, and the like),
while others may be harmful (bee pollen, dehy-
droepiandrosterone (DHEA), ma huang, and the like). - The use of creatine and caffeine as ergogenic aids has
been supported by research in some instances. Some
research does support creatine supplementation in
high-intensity strength activities such as resistance
exercise (Kreider et al, 1998). A common side effect
of this product is weight gain. Most studies that have
investigated creatine have used creatine phosphate
supplementation for 5 to 7 days (20 g/day) followed
by a maintenance dose of 2 g/day. - Caffeine is a stimulant that may have ergogenic
effects in those who respond to supplementation
(Bruce et al, 2000). Possible side effects include upset
stomach, nervousness, irritability, and diarrhea.
Caffeine is a banned substance at college, national,
and international competitions; however, ergogenic
benefits can be seen with as little as 5–6 mg/kg body
weight, and positive drug tests are not likely at this
level (Pasman et al, 1995). Tea, coffee, and sodas with
caffeine can provide 50–100 mg/serving.
•A careful review of literature is necessary when deter-
mining if an ergogenic aid should be consumed. Most
advertisements use personal testimonials that may be
convincing, but are not based on research that has
been duplicated and widely accepted. Some health
care professionals oppose the use of all nutritional
88 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE