By Barbara J. King
Scrolling through my Twitter feed this weekend, I saw a tip to follow biological anthropologist Bryce Carlson at Purdue University. I did — and wow! A fascinating new window on the science of extreme human endurance opened up.
Carlson heads an interdisciplinary team that will study the responses of a dozen athletes as they run the Race Across USA, a 3,080-mile event that gives new meaning to the word "marathon." Starting in Huntington Beach, Calif., on Jan. 16, the race will conclude at the White House in Washington, D.C., 140 days later.
Though the race organizers' main goal is to raise awareness about childhood health and fitness in an age when kids' obesity is a crisis, Carlson's team's focus on the adult runners is holistic: It spans everything from the athletes' cardiovascular and gastrointestinal health to their patterns of sleep and the nutritional choices they make as they experience intense stress in body and mind.
Carlson isn't just the race's research director, though — he's also one of the 12 runners.
The idea of Carlson and 11 other athletes running the equivalent of 117 back-to-back marathons pretty much stuns me. I've never been athletic and I constantly fight with myself to get the exercise that I know I need for good health. I was excited to reach out to Carlson, and he kindly participated in an email interview with me on Monday. Here are some highlights:
BJK: I'm keenly interested in the vast gap between the levels of physical activity our hunter-gatherer ancestors engaged in and what most of us manage today. Even for people who exercise or work out through the week, our lives are still comparatively more sedentary. But hunter-gatherers were not running 3,080 miles in 140 days! Is there an evolutionary context for such an extreme endurance event?
BC: I don't know that I agree with the idea that there is a vast gap between hunter-gatherer activity and modern humans. There is certainly a lot of variation in modern human activity patterns, but I think HG (extant and extinct) activity levels fall within the range of variation we see around the world today. Plenty of modern humans work in manual labor, or commute long distances on foot or bike to work each day. Many of the runners I'll be racing with are probably training 3+ hours per day, burning an additional 1,500-3,000 kcal on top of their basal metabolic needs. That's a pretty high level of physical activity and I haven't seen a lot of data suggesting HGs in any environmental context are that active on a sustained basis.
The Endurance Running Hypothesis, the idea that a number of morphological adaptations at the origins of genus Homo were intimately tied with endurance running, is certainly relevant to our study here. But, then again, I don't think anyone is arguing that these hominins [human ancestors] were engaging in 3,000-mile treks over the course of a few months. Or covering 26+ miles per day on a sustained basis. It seems to me we (humans) have this capacity for endurance running, and I'm incredibly interested to explore where the edges of this capacity lie: biomechanically, physiologically, energetically, nutritionally and psychologically.
At the same time, humans use culture as well as biology to adapt to novel stresses. Our ability to overcome environmental obstacles has only increased with advances in technology. Endurance running may have a deep evolutionary history in our species, but it's only today that runners benefit from research in exercise physiology and nutrition science, as well as product development in sports nutrition, shoes and apparel, and recovery aids (e.g., foam rollers, compression gear). These advancements in knowledge and technology buffer runners from physical stress associated from long-distance running (to the extent that they use it appropriately), and therefore allow runners to go farther and faster than they ever have before.
BJK: In reading about the interdisciplinary research team's plans, I'm wondering how invasive the process will be to the runners themselves, including you — blood draws, equipment worn, running across special research plates, questionnaires filled out. Is this a lot to ask of the athletes?
BC: This was a key part of the research design. As a runner and race participant, as well as research director, I wanted to make sure that all data collection was minimally invasive and in no way inhibited the runners' ability to complete the race. So, that really limited the kinds of questions we could ask. I would have loved to get daily blood samples and weekly muscle biopsies. We could have established a brilliant data set of biomarkers for metabolism, or muscle breakdown and adaptation. We could have tested morphological and epigenetic adaptation from mitochondrial density to mtDNA and nDNA gene regulation. But we would have had very few runners, if any, agree to participate. Those who would have participated, would have been [at] a significant competitive disadvantage, and so those kinds of measures didn't pass my standard of ethical appropriateness.
The protocols we've designed have incorporated feedback of the runners, and my own sense of what's appropriate, and right now it looks like we have buy-in from most of the runners on all parameters of the study. In general, the runners are all really excited about participating!
BJK: How much diversity is represented in terms of gender, age and population background ("race") among the runners?
BC: Right now, we have 10 men and two women. Runners range in age from late 20s to post-retirement. Unfortunately, not a lot of ethnic diversity, although there is a lot of socioeconomic diversity. That said, most aspects of the research program are set up to use each runner as their own control. So, rather than a limited sample size of 12, we have 12 populations with upwards of 120 data points (one for each day of the race) each.
BJK: What do you hope to learn from this race that will benefit all of us who aren't extreme athletes?
BC: At the most fundamental level, we're looking at defining the processes of adaptation. I think many people shy away from physical activity (or personal growth in any number of other dimensions) because they don't see the pathway between the person they are and the person they could become. My goal with this study is to illuminate that process. Even the "extreme" athletes need to adapt. We may have different genetic capacities, but there is a process of becoming that is universal. And I would much rather we (society) focus the conversation on that process, because it's something we all have control over and we can all do. Our process might take us across the country, but there's no reason that process can't take others from the couch to comfortably walking up and down a couple flights of stairs. Or climbing a mountain. The endpoints might differ, but we're all capable of becoming a little stronger, or more resilient, than we are.
BJK: How are you personally preparing for this race? I know you've run a race of 153 miles — am I right that is your longest so far? Do you worry about the inevitable physical pain, and the stressful double duty you'll be facing as participant and race research director?
BC: Well, my approach may be a little counterintuitive. I'm actually running less and resting more. After my 153-mile race last September, I took a couple weeks off before ramping up my training again. After a few weeks I started to feel some early symptoms of overuse injuries, which prompted me to back off. At this point, I think the most important thing I can do to prepare is make sure I reach the starting line healthy and injury free. And so my focus has become fewer weekly miles, a little more strength training, and yoga.
In terms of the stress of double duty, I think I'm at the peak of it now. [Soon], I just get to run.
What I love about this whole race project is its marriage of interdisciplinary scholarly work and applied public-outreach work that, as Carlson says, can touch us all: We're all capable of becoming a little stronger, or more resilient, than we are. This has been a big-deal issue for me in working on recovery from all the toxicities of intense chemotherapy and radiation last year and early this year, and I think applies to many of us no matter what our own particular health or life challenges might be.
If you'd like to run part of the race, or just want to follow along as the race unfolds, here's more information and the route map. I plan to check in with Carlson once the race begins.