CHO metabolism during prolonged exercise (~72% VO 2max ) to exhaustion w/ and w/out CHO feedings (every 20 min) Coyle et al., JAP, 1986

Fat metabolism during prolonged exercise (~72% VO 2ma x) to exhaustion w/ and w/out CHO feedings (every 20 min) 1 hr2 hr3 hr4 hr Placebo CHO RER data Coyle et al., JAP, 1986

Substrate use during exercise to exhaustion w/ and w/out CHO feeding Coyle et al., JAP, 1986

Fluid & CHO Intake during Exercise  water (placebo)  5% glucose polymer  6% glucose/sucrose solution  7% glucose polymer/fructose Murray et al., MSSE, 1987

CHO and fluid feeding during intermittent exercise  no difference for plasma Na + or K +  no difference in RPE  no difference in RER  no difference in plasma La  no difference in Power 1 (240 revolutions)  time of Power 2 (480 revolutions) shorter for sucrose/glucose and glucose polymer/fructose trials  most complaints with glucose polymer trial Murray et al., MSSE, 1987

Hepatic glucose output (HGP) and glucose uptake (Rd) w/ and w/out CHO feedings during prolonged exercise (~70% of VO 2max ) McConell et al., JAP, 1994

CHO Feeding during Prolonged Exercise   blood glucose  maintains CHO oxidation rate   time to exhaustion/performance  conserves liver glycogen   muscle glucose uptake   plasma insulin   plasma FFA  no effect on muscle glycogen utilization (in cycling studies)

CHO feeding during prolonged exercise  time of CHO feeding  few differences in CHO type  upper limit of exogenous CHO oxidation  difference in CHO oxidation between running and cycling protocols?

Early studies on diet and performance  high-fat diet  RER and  RPE (Krogh & Lindhard, 1920)  correlation between blood [glucose] and physical condition at end of Boston Marathon (Levine et al., 1924)

Bergström et al., Acta Physiol Scand, 1967

Bergström & Hultman, Scand J Clin Lab Invest, 1967

Benefits of CHO Loading   muscle glycogen stores   time to exhaustion  no benefit on performance of <90 min (Hawley et al., 1997; Madsen et al., 1990)

Effects of High-CHO Diet   time to exhaustion   muscle glycogen stores   use of CHO for energy Effects of High-fat Diet   plasma [FFA] and FFA uptake   IMTG   use of fat (70% from IMTG) for energy   ß-oxidation enzymes

Hawley et al., J Sports Sci, 1995

Point 5: A high-CHO diet maximizes performances during training (TD Noakes, MSSE, 1997)  Athletes do not each high-CHO diets during training.  Literature doesn’t support that dietary-CHO during training diminishes training or performance (Lamb et al., 1990; Sherman & Wimer, 1991; Simonsen et al., 1991).  Studies have shown that a period of adaptation to low-CHO diet may improve subsequent performance (Lambert et al., 1994; Muoio et al., 1994)

Effect of High-Fat Diet

Early Studies of Diet Effects

Effect of Dietary CHO in Untrained Subjects

Effect of CHO intake on muscle glycogen and rowing power (3x2500 m) Simonsen et al., JAP, 1991 * * Week 4 was significantly greater than low-CHO diet group

Effect of Dietary CHO on Muscle Glycogen Repletion Costill & Miller, Int J Sports Med, 1980

Sport Nutrition: Carbohydrate Before exercise  CHO intake helps “top off” glycogen stores During exercise  CHO intake not important until later in exercise (but before onset of fatigue) After exercise  high CHO intake increases rate of glycogen storage – CHO type doesn’t matter