CHO metabolism during prolonged exercise (~72% VO2max) to exhaustion w/ and w/out CHO feedings (every 20 min)

Coyle et al., JAP, 1986

Fat metabolism during prolonged exercise

(~72% VO2max) to exhaustion w/ and

w/out CHO feedings (every 20 min)

1 hr 2 hr 3 hr 4 hrPlacebo .85 .84 .80 --

CHO .85 .86 .86 .85

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 VO2max)

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 storesDuring 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