‘Tis the season for marathon training. The Kiawah Island Golf Resort Marathon celebrated its 37th race last weekend and the 5th annual Charleston Marathon is January 17, 2015. Both of these races also offer a half marathon (13.1 mile) option which, after the 5K, is the most popular race distance. While a portion of these runners are considered “elite,” the balance are likely running enthusiasts who can benefit from incorporating a planned nutrition strategy to improve their training and even impact finishing times.
A recent study tested the impact of a “scientifically based nutritional strategy” (SCI) on the marathon performance of non-elite runners. Compared to the group that used a “freely chosen” nutrition plan, those in the SCI group followed the strategy below and completed the race approximately 5 percent faster than the other group.
The faster group likely benefited from these key nutrients:
Sugar or carbs – the body stores sugar in the muscles and liver as glycogen, the body’s preferred source of fuel for endurance sports like running
- Before the run, topping off glycogen stores by eating breakfast or consuming a sugar source (via a gel, for example) is critical.
- Muscles store about 45-90 minutes worth of glycogen and when they are depleted, you “bonk” or “hit the wall.” You can improve performance during hard exercise by taking in carbs during the workout. Here are some guidelines: Include 120-240 calories from carbs (30-60 grams) if you are exercising for more than 1 hour; include 240-360 calories from carbs (60-90 grams) if you are exercising for more than 2 ½ hours; and do not worry about taking in extra calories if you are exercising for less than an hour.
- Consume your nutrition source slowly so blood isn’t diverted from the working muscles to the gut, which can cause nausea.
- Replete glycogen stores by eating some complex carbs after the race.
|10-15 minutes before the race||2 gels with 200 mL water|
(each gel providing 20 g glucose, 20 mg sodium, 30 mg caffeine)
|40 min. after starting the race||1 gel|
|Every 20 minutes for remainder||1 gel|
|Every hour||750 mL of water|
|Total||60 g glucose, 60 mg sodium, 90 mg caffeine, 750 mL of water/hour|
Sodium – If you sweat excessively or are doing more than 90 minutes of exercise, you many need to consume some of this important electrolyte to stimulate thirst, replace sodium lost in sweat, help maintain fluid balance and enhance fluid retention.
- The American College of Sports Medicine recommends 110-170 milligrams of sodium per 8 ounces of fluid. Many sports drinks, in fact, are sodium-poor.
- Hyponatremia, a condition where blood sodium levels get too low, can occur among marathon runners and generally occurs among those with higher sweat losses, those who over-consume water before or during an event and those who accumulate too much water by consuming it faster than their bodies can make urine.
- Most recreational athletes don’t need anything more than water to hydrate.
Caffeine – There is strong evidence that caffeine can improve performance, help athletes train harder and longer and make the effort seem easier.
- The target dose is about 1.5 milligrams per pound of body weight or 225 milligrams for a 150-pound person. An 8-ounce cup of brewed coffee has about 70 milligrams.
- More caffeine tends to cause jitters, nausea, anxiety and possibly gastrointestinal distress but not better performance. Caffeine had at one point been considered a diuretic but current research shows caffeine is not dehydrating for those who are used to consuming it.
Water – Most of the body’s weight – about 75 percent – is water. During exercise, it is lost by sweating and through increased expiration. A loss of 1 percent of your body weight increase the heart beat an additional 3-5 times per minute and decreases the efficiency of getting adequate oxygen to the muscles. A loss of 2 percent of body weight is true dehydration which can cause the body temperature to rise, the heart to beat faster, glycogen to deplete more quickly and mental fatigue to set in. A loss of 9-12 percent body weight can lead to death.
- It is easy to underestimate fluid needs and thirst is a poor indicator of fluid status.
- The best way to determine how much fluid you need during exercise is to weigh yourself before and after a run and use that as a guideline for your next run. For every pound lost, drink 1.5-2 times that in cups of fluid slowly throughout the run (e.g. a 3-pound loss requires six cups of fluid, spaced equally throughout the run).
Whether you are training for a race with the goal to ‘just finish it’ it or are trying to beat your personal record, your nutrition has an effect. Play around with some different methods during training - just don’t ever try something new on race day – and learn how to use food as fuel to improve your performance.
Debbie Petitpain, RDN, is a Sodexo Wellness dietitian in MUSC’s Office of Health Promotion.