Health, fitness, and performance are often seen as interchangeable metrics. After all, having high levels of each is important when it comes to being able to train for—and achieve—your running goals.
But what do these terms really mean and how are they all related to one another when it comes to putting one foot in front of the other? We asked two exercise physiologists to break it all down.
What Does It Mean to Be Healthy?
Being physically healthy, in a general sense, means that your body systems work well and efficiently to allow you to engage in daily activities, resist disease, and recover well from stress and illness, according to Grace Horan, M.S., an ACSM-certified exercise physiologist at the Hospital for Special Surgery (HSS).
“Specifically, cardiovascular fitness and musculoskeletal health are two variables that are significant predictors of general health that can be positively influenced through exercise,” Horan says. “Maintaining good health is essential for longevity and to maintain a good quality of life as well as for prevention of injury and disease.”
Run coach Janet Hamilton, R.C.E.P., C.S.C.S., agrees. There’s not one defining characteristic to being in good physical health, she says, but broadly speaking, your body is functioning optimally for its age and environment. “A healthy body is better able to fight off disease as well as adapt to changing conditions—both physical and mental,” she says
How to Train for Better Overall Health
You can build overall health by doing aerobic exercise at a moderate intensity for 150 minutes per week or vigorous physical activity for 60 minutes a week, according to Hamilton. This breaks down to 30 minutes of moderate-intensity activity (like brisk walking) five days a week or 20 minutes of vigorous-intensity activity (like your favorite activity, running) three days a week. In addition, it’s important to strength train two to three days per week, Hamilton says.
While the above recommendations are backed by the Centers for Disease Control and Prevention (CDC), a 2024 study in Circulation found that those who exercised at a moderate intensity for 300 to 599 minutes per week saw the most health benefits. For instance, researchers found those who exercised this much had a lower risk of early death from all causes, including heart disease.
What Does It Mean to Be Fit?
“Fitness, in the big picture, is the ability to perform activities with optimum strength and endurance,” Hamilton says. “It’s a broad definition for a reason—because each individual’s needs may be different.”
With that being said, there are a few variables that can determine physical fitness in relation to running, according to Horan. “While aerobic capacity is an important factor that provides information regarding physical fitness, it’s important to consider other variables such as anaerobic threshold, running economy, and velocity at VO2 max,” she says.
Aerobic capacity refers to the maximum amount of oxygen your body can use at one time during vigorous exercise, Horan says. It’s measured by assessing your VO2 max, which is measured as milliliters of oxygen per kilogram of bodyweight per minute, according to Harvard Health. The higher your VO2 max, the better your body is at taking oxygen from the air and delivering it to your muscles to perform at their best. That’s a fancy way of saying someone with a higher VO2 max is fitter than someone with a lower VO2 max.
Anaerobic threshold is the highest intensity you can exercise at for a prolonged period of time without lactate building up in your blood, Horan explains. (Lactate is a chemical your body produces when your cells break down carbs for energy and feels like a burning sensation in your muscles, per the National Library of Medicine.) The higher your anaerobic threshold, the faster and longer you can run without tiring out, according to Horan.
Running economy is a measure of how fast you can run using a given amount of oxygen, Runner’s World previously reported. If you can run faster than someone else while using the same amount of oxygen as the other person, you’re more efficient, or economical. “Two individuals may have the same aerobic capacity, but the individual that is able to utilize energy more efficiently at a given pace is more likely to perform better during a race,” Horan says.
Being physically fit is important not only to improve performance when running, but also to support overall health and longevity, according to Horan. “Individuals with greater cardiovascular fitness are often at lower risk for developing cardiovascular and metabolic disease in the long run,” she says.
How to Train for Better Fitness
To improve your fitness, you need to push beyond your body’s current capability and challenge it either with running for longer periods or time or at higher intensities, Hamilton explains. For most people that means building a weekly mileage base or adding in some higher-intensity running (speedwork) once a week. “Overload provides the stimulus for adaptation,” she says.
However, if you overload every run, you’ll fail to provide the recovery your body needs, and your body will break down from the overload rather than get stronger, according to Hamilton. While the amount of recovery you may need varies from person to person, it’s best to have at least one rest day per week, and maybe even two if you’re new to running, Runner’s World previously reported.
What Does It Mean to Perform Well?
Optimal performance can mean something different to every runner, according to both Horan and Hamilton. “Certainly you can point to the elite Olympians and say they’re performing ‘well,’ but there are also mid- and back-of-the-pack runners who are performing at their individual best for that given moment in time,” Hamilton says. “Just because they finish a race well back from the overall winners doesn’t take away from the fact that they are performing at their best.”
With that being said, runners with high aerobic capacities are known to exercise with greater relative ease, meaning that they can often endure faster speeds for longer periods of time, Horan explains.
“Specific to endurance athletes, metabolic efficiency, which relates to the ability to utilize fats and/or carbohydrates at different workloads, is very important [for performance], as increased reliance on fats during low- to moderate-intensity portions of a race will allow for individuals to save limited carbohydrate stores for the more intense portions of the race, which will decrease the need to fuel with gels, bars, and drinks that can cause GI disturbances, interfering with running performance,” Horan says.
Additionally, runners with higher lactate (anaerobic) thresholds have a greater ability to exercise below their threshold, “which leads to less lactate accumulation in the blood, and an increased capacity to continue running for longer periods of time without pronounced fatigue,” Horan says.
If you’re interested in learning more about how to perform at your best, Horan recommends scheduling an assessment with an exercise physiologist, who can evaluate your aerobic capacity, metabolic efficiency, and lactate threshold and help you improve these elements.
How to Train for Better Performance
“To train for better performance, you need to first define what you’re trying to do,” Hamilton says. “Is your ‘performance’ an upcoming race distance you’ve never done before? Then perhaps the first aspect to conquer is the endurance base needed to complete the given distance at a race effort.”
For instance, if you’re training for your first 5K, you’ll want to set aside four days a week to run and three days a week to cross-train or rest. If your goal is to break four hours in the marathon, you’ll want to run five days a week—focusing on a mix of long runs, speed training, hill workouts, and recovery runs—and rest or cross-training two days a week. (FYI: We have a ton of different training plans here at Runner’s World, so take a look and see which one works best for you!)
The bottom line: To improve as a runner, you’ll need to build enough of an endurance base to sustain the duration of the activity you’ve chosen and continually challenge your body to adapt, Hamilton says.
Danielle Zickl is a freelance writer who has 10 years of experience covering fitness, health, and nutrition. She’s a graduate of Ithaca College. You can find her work here on Women’s Health, and in many other publications including PS, SELF, Well+Good, Runner’s World, Outside RUN, Peloton, Men’s Fitness, and more.
