Masters runners who hold their training volume close to its previous level lose about 5% to 6.5% of their maximal aerobic capacity per decade, according to a review of studies on aging endurance athletes. Those who cut volume by more than 20%, or drift toward inactivity, lose between 15% and 46% per decade. Changes in training volume explain 54% of the variation in that decline among men and 39% among women. A half marathon block after 40 is therefore a question of staying in training for the full block, and that depends on eating enough to finish each session and recovering well enough to start the next one.
Fat and Carbohydrate Use at Different Paces
Trained masters athletes burn fat efficiently. Their peak fat oxidation occurs at roughly 59% to 64% of maximal aerobic capacity, compared with 47% to 52% in the general population. Easy mileage draws heavily on that supply.
Tempo runs, intervals and the final miles of a long run are different. As pace rises, the body uses a larger share of carbohydrate, and stored carbohydrate in muscle and liver is limited. A runner can feel fine for 40 minutes at an easy effort and then fade during a threshold segment because the fuel that segment needs was never eaten.
Carbohydrate Intake on Training Days
A consensus paper by Louise Burke and colleagues in the Journal of Sports Sciences set daily carbohydrate targets by training load. Moderate training of about an hour a day calls for 5 to 7 g per kilogram of body weight. Endurance programs of 1 to 3 hours a day call for 6 to 10 g/kg. At 70 kg, the low end of the moderate range is 350 g of carbohydrate in a day.
Older athletes often eat less than this. Researchers who used 24-hour dietary recall at the World Masters Athletics Championships found average carbohydrate intake below the recommended range for endurance athletes, and protein intake was short in most groups as well. Adding a starch to each meal on days with a quality session makes up much of that shortfall, along with a carbohydrate-based meal or snack 1 to 4 hours before the run.
Fuel During Runs Longer Than an Hour
Long runs pass the 60-minute mark by the middle weeks of most half marathon plans, and race day lasts longer for most people in this age group. An Outside analysis of about 1 million 2024 results put the median half marathon time at 2:03:53 for men aged 40 to 49 and 2:24:15 for women in the same bracket. At those durations, food taken during the run affects the result.
The American College of Sports Medicine recommends 30 to 60 g of carbohydrate per hour for exercise lasting longer than an hour. More recent work suggests 60 to 90 g per hour can help in a half marathon if the stomach tolerates it. Long runs are the place to test those amounts, since race morning is a poor time to learn what the gut rejects.
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