Runners and endurance athletes often talk about their personal records (PRs), upcoming races, or the latest fitness tech or gadgets. But there’s always a looming question: How long can I keep going? Physical activity can delay signs of aging by promoting heart health, preventing low bone mass, improving coordination and balance, and lowering the risk of chronic diseases . But endurance athletes also place unique strains on their bodies which can impact healthy aging and their longevity in their sports. One of these strains is oxidative stress—which also naturally increases with age. Let's take a look at how oxidative stress and certain blood biomarkers play a role in longevity on and off the course.
Oxidative stress increases with aging and training
Free radicals are reactive, unstable molecules formed by natural processes like exercise and the breakdown of food as well as from external sources like pollution and chemicals.  Excessive free radicals in the body can lead to oxidative stress, which can result in chronic inflammation and cellular damage—contributing to accelerated aging.  With age, the body has a decreased capacity to fight free radicals and prevent this oxidative stress and damage, which has also been connected to diseases including autoimmune diseases, diabetes, and Alzheimer's. 
Exercise also is known to increase the production of free radicals in the body . A recent systematic review on the effect of running on oxidative stress found that training status of an individual (which includes the intensity and duration of their exercise) impacts markers of oxidative damage.  Another study found that, while endurance and ultra-endurance events resulted in negative changes in oxidative stress balance, they could be blunted and reduced by adequate training prior to the event. 
Age- and training-induced oxidative stress can be managed
Though it’s impossible to completely eliminate free radicals and oxidative stress, temporary increases in oxidative stress from exercise, acute injury, or illness can be managed.  First, proper training and recovery can condition the body for intense bouts of activity. Antioxidants can also help to keep levels of oxidative stress from exercise get out of hand. Antioxidants are chemicals that lessen or prevent the effects of free radicals by stabilizing them and, therefore, making them less harmful to the body. Antioxidants are naturally produced in the body and can also be obtained through the diet.
Tips to improve: To mitigate the effects of oxidative stress, prioritize rest days and integrate lower impact exercises, particularly with age. For example, running at a high intensity and duration five to six days a week may not be attainable throughout the lifespan. Walking and yoga are great substitute activities. Also be sure to include plenty of fruits, vegetables, nuts, and seeds in the diet, as they are high in antioxidants like vitamins C and E.
Blood biomarkers to optimize for prolonged performance and longevity
PR-setting and goal-clinching are some of the most common athletic motivations. But many athletes have also begun prioritizing performance and longevity—the ability to participate in the sports they love at any age. And oxidative stress isn't the only factor that contributes to someone's ability to maintain performance and longevity. Various blood biomarkers act as important targets for maintaining optimal health and a strong body that can thrive under physical pressure. While each person may need to focus on optimizing different biomarkers, here are some of the top biomarkers that can directly impact longevity in sport:
Glucose is the body's primary source of fuel. Properly regulated glucose levels are essential for maintaining overall health, performance, and longevity. And though glucose levels normally fluctuate throughout the day—especially after meals—high fasting glucose levels can indicate an issue with how the body processes glucose. Glucose can also be elevated due to stress or a poor night's sleep. Glucose regulation also can decline with age. 
Tip to improve: Eating balanced meals and snacks can help regulate blood sugar levels, and exercise can increase sensitivity to insulin (the hormone that lowers blood sugar).  Eat more high-fiber fruit, particularly blueberries! They are high in polyphenols called flavonoids, which have been linked to better brain health with aging, reduced risk of cognitive decline, and healthy muscle recovery.  Combine berries with a source of protein or fat, like a cheese stick or nuts, to keep blood sugar more stable.
Vitamin D is an important fat-soluble vitamin that promotes healthy aging. It helps the body absorb calcium, which helps maintain bone strength, which becomes critical with age. Vitamin D also helps to regulate the nervous and immune systems. Inadequate vitamin D increases the risk of low bone mineral density, making a person more susceptible to stress fractures. Low vitamin D has also been linked to poorer sleep quality, which can be highly detrimental to recovery from intense physical activity. 
Tip to improve: Aim to increase food sources of vitamin D such as salmon, egg yolks, fortified dairy products, swordfish, and cheese. Only supplement with vitamin D if blood test results show an inadequacy or deficiency of vitamin D levels.
HsCRP is a general marker of inflammation and a critical indicator of performance and recovery. High levels of strenuous exercise can increase inflammation and cause markers like hsCRP to stay elevated. And while some acute inflammation is necessary for the body to grow and repair muscles, uncontrolled inflammation can halt muscle gains. It can also put you at a greater risk of getting sick.
Internal inflammation is also connected to oxidative stress and accelerated aging, so mitigating excess post-workout inflammation is a priority as we age through sport.
Tip to improve: Incorporate regular rest days into your training routine to allow for proper recovery and mitigate inflammation. 
Cortisol (AKA the stress hormone) levels increase with heightened emotional and physical stress, including exercise. Cortisol is a catabolic hormone, meaning that it breaks muscle down. So when levels of cortisol are chronically high, athletic performance and post-workout recovery can decline. Elevated levels of cortisol are also associated with higher blood sugar levels, age, and sex (women typically have higher levels than men). [13,14]
Tip to improve: Focus on sleep quality. The body undergoes a lot more stress from poor sleep habits than you may realize. Adequate sleep (more than seven hours per night) is essential to helping your body recover.
Magnesium is a mineral that supports healthy blood pressure and blood sugar levels, strengthens the immune system, and assists in muscle contraction and relaxation.  Adequate levels of magnesium in the body improve muscle strength and increase the time to muscle fatigue during short, intense bursts of exercise. Optimal magnesium levels are also associated with improved sleep quality, mood, and recovery from strenuous exercise. Magnesium deficiencies are more common in older adults and are also linked to oxidative stress. 
Tip to improve: Increase magnesium intake through eating foods like salmon, pumpkin seeds, and beans. A magnesium supplement may be warranted if a blood test identifies low levels.
- Running and aerobic exercise can cause oxidative stress. This can negatively affect health and performance if not balanced with appropriate antioxidant activity.
- Training status—which includes a balance of training load, training intensity, and recovery—impacts oxidative stress.
- Performance improvements can be paired with strategies to also promote healthy aging.
- Biomarkers that directly impact both performance and healthy aging include: blood glucose, vitamin D, hsCRP, LDL cholesterol, cortisol and magnesium
- In addition to personalized recommendations from InsideTracker’s blood biomarker analysis, a balance of exercise, adequate rest, and nutrient-dense foods can help athletes on their journey for longevity in sport.
Stevie Lyn Smith, MS, RDN, CSSD, CDNStevie Lyn is a Content Strategist and Team Nutritionist at InsideTracker. As a Registered Dietitian and Ironman triathlete, she enjoys combining her passions to help educate others on how to fuel for overall health and performance. When she’s not swimming, biking, or running with her dog, you’ll find her in the kitchen working on a new recipe to improve her biomarkers.