Carbohydrate loading

Carbohydrate loading is a high-carbohydrate diet in the days before an endurance event to raise muscle glycogen above normal.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.} Running low on muscle and liver glycogen causes fatigue in long aerobic events; loading makes more carbohydrate available in the later stages.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 220.} It suits distance runners, road cyclists, cross-country skiers and other clients at risk of running their stores down.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.}

A common carb-loading regimen is three days at 8 to 10 g/kg of carbohydrate a day during a taper the week before, with complete rest the day before the event.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.} That should raise muscle glycogen 20 to 40% above normal.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.}

In practice

• Higher intakes of 10 to 12 g/kg a day over the final 36 to 48 hours have been suggested before a marathon.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.} Triathlon guidance uses the same figure, which for a 70 kg client means 700 to 840 g of carbohydrate a day.^{3USA Triathlon, Complete Triathlon Guide, p. 149.}
• A depletion phase beforehand isn’t needed.^{3USA Triathlon, Complete Triathlon Guide, p. 149.} Well-trained runners have reached supercompensated glycogen levels with three high-carbohydrate days during the taper alone.^{3USA Triathlon, Complete Triathlon Guide, p. 149.}
• Results in women are mixed.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.} In one study men raised their muscle glycogen and women didn’t, possibly because the women’s carbohydrate or calorie intake was too low.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.}
• Outside endurance sport the case is weaker.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.} Soccer players ran farther on a 65% carbohydrate diet, but individual responses varied widely, and a higher-carbohydrate diet didn’t improve power across four sets of jump squats.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 221.}