The Scientific Research on How to Prepare Yourself to Run Back-to-Back Marathons
For most people, training for a single marathon is enough.
But a growing number of runners desire something more. They’ll run two in a weekend, or four in a month, or even four or five marathons on consecutive days. Other runners seek out several-day-long ultramarathon events, contested in stages similar to the Tour de France.
The rising popularity of becoming a “marathon maniac” or completing multi-stage ultras has demonstrated that these sorts of feats are indeed doable by thousands of runners.
While there’s no problem with running consecutive marathons, it’s readily apparent that doing multiple marathons in a short time period isn’t going to net you a big PR.
But if your heart is set on back-to-back marathons or a staged race, you may want to know more about how these events affect your body.
How the body responds to racing long distances
Fortunately for us, this is beginning to be addressed by scientific research.
Since the population of runners who partake in these extreme endurance events is so small, studies on their effects are limited to case studies of single individuals, or observational studies of small groups.
Even though these studies are limited in size and scope, they nevertheless offer some answers on how your body copes when you push the limits of long-distance endurance.
A 2008 study by researchers in Switzerland and Germany examined changes in body composition in 10 men who competed in a 17-day, 750-mile race across Germany, measuring changes in hydration, body weight, muscle mass, and fat mass throughout the course of the grueling race.
Over the course of the event, the men lost almost nine pounds of fat and four and a half pounds of muscle.
Interestingly, their weight did not change significantly: the loss of muscle and fat was made up for by an increase in total body water.
The authors proposed a number of potential explanations for these results.
Muscle proteins breaking down from the pounding of 40 miles a day could have overloaded the kidneys, which increased total body water percentage, or the body may have actually “eaten” the muscles for fuel or nutrients, causing a shift in hormone levels which control water retention.
The authors noted that they did not measure an essential variable—dietary intake during the race, which could have a significant impact on the body’s response. The muscle and fat loss could also be chalked up, in part, to inadequate caloric intake.
Caloric intake for multi-day races
Research on a few multi-day endurance events has found that it can be very challenging to meet daily caloric requirements given the constraints of the event.
- A study of four cyclists competing in a 3,000 mile cycling relay race found that each cyclist’s daily workload required 6,400 Calories of energy, but the cyclists only averaged a daily intake of 4,900 calories, creating a significant deficit by the end of the race.
- Similarly, a case study of a competitor in a five-day, 1,400-mile cycling race in the Alps found that the competition incurred a 8-11,000 Calorie deficit, resulting in loss of body and fat mass.
- Returning to running, a case study by Rebecca Hill and Peter Davies followed a two-week segment of an ultramarathoner’s run around the circumference of Australia (9,000 miles). Using a highly sensitive measurement technique, Hill and Davies determined that the runner’s average energy requirement during each of his 40-55 mile days was about 6,300 calories. The authors were not able to determine his daily energy intake, but the runner only lost about three pounds of weight during the two-week observation, and at the end of his 195-day run, he had only lost a total of two pounds, proving it is possible to maintain an equilibrium of energy intake even during such an event.
These cases are obviously extreme, but they illustrate something important: your energy requirements are enormous during multi-day endurance events, whether it’s a staged ultramarathon or several marathons in a week.
If you’re taking part in these kinds of events, your caloric intake will need to be at least double what it usually is.
And, unlike running a single marathon, you can’t just refuel with carbs alone. The demands of extreme endurance events require protein and fat as well—not to mention fluids.
The ultramarathoner studied by Hill and Davies turned over 1.6 gallons of water per day!
Now, if you’re not doing 40 or 50-mile days in Australian heat, you do not need quite so much, but the point stands: extreme events require extreme fueling.
Recovery from marathons
One import consideration when racing consecutive marathons is recovery between races.
Both of these studies clearly indicate that the body needs at least 7-10 days of rest post marathon to fully recover from the cellular damage caused during the race.
Another scientific study conducted on the calf muscles of marathon runners concluded that both the intensive training for, and the marathon itself, induce inflammation and muscle fiber necrosis that significantly impaired muscle power and durability for up the 14 days post marathon.
As such, recovering from your first marathon is essential to success at your next race.
How to recover properly
To ensure that you’re optimally recovered before your second race, jump starting the recovery process immediately after the first race is essential. Here is a quick outline of the ideal recovery process:
- Hydrate as soon after your race as possible with Gatorade or electrolyte drink. You want something with sugar to stimulate the insulin response.
- Eat a small meal or snack that contains a 4 to 1 ratio of carbohydrates to protein. If you can handle eating more than a small meal, eat as much as you can.
- Perform a quick cool down. If you’re more experienced, this can be a very light jog for 10-15 minutes. If you’re a beginner runner or very sore, walk for 10-15 minutes. Stretch major muscle groups and anything that is sore or tight. Roll out any nagging injuries or problem areas.
- Take an ice bath as soon as you can after the race.
- Eat another decent sized, healthy meal 2-3 hours after the race.
- Nap, put your feet up, or get a massage.
- Take an Epsom salt bath before bed.
- Roll out on a foam roller or with the stick and stretch well.
- Get plenty of sleep.
Admittedly this routine is extensive, but it will drastically improve your rate of recovery and help get you back to training for the second race as quickly as possible.
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It’s a fairly safe conclusion that improper fueling during multi-day events will lead to poor outcomes and possibly health risks as well.
We also can conclude that failing to focus on recovery between events will significantly hinder future performance.
Beyond this, there isn’t enough evidence to draw any conclusions on whether multi-day ultras or back-to-back marathons have any long-term health implications, either from an injury or overall health perspective.
Some (though not all) studies of marathon finishers show increased levels of proteins that indicate heart damage, so there is some concern that running several marathons in a short period of time could exacerbate this damage, but there simply isn’t enough research yet to draw any firm conclusions.
At the very least, the athletic accomplishment of ultra-endurance runners and marathon maniacs demonstrate that at least some portion of runners are able to thrive and even make a second career out of multi-day events or several marathons in quick succession.
If this is something you’d like to try, the biggest take-away from the science so far is that proper fueling and focus on recovery is paramount to preserving your body’s integrity.