It is not hard to imagine that professional athletes would tend to have healthy blood. Exercise takes a lot of oxygen. Red blood cells carry oxygen, so the body makes more red blood cells to carry more oxygen the more athletes exercise. The oxygen-carrying molecule hemoglobin does double duty for athletes. Not only do high hemoglobin levels result in a greater oxygen-carrying capacity for the bloodstream, they also cause the release of a chemical called nitric oxide (NO) that dilates blood vessels so more oxygen can be carried to muscles. 
Does exercising, and especially running, help people increase their red blood cell count, though, and why is that? If you have a low red blood cell count, what should you know about the best workouts for you?
How does exercise increase red blood cell count?
Red blood cells are made by the bone marrow. Exercise causes bone marrow to grow. Regular physical activity also induces the release of hormones that increase the production of hemoglobin.  Athletes who train under conditions that require even more oxygen, such as those who are training at high-altitude locations, develop even more red blood cells with even more hemoglobin .
Do exercise and running increase red blood cell count for people who live with health challenges?
So, regular exercise increases the red blood cell count for serious or professional athletes, but what about those of us who aren't athletes, who can't afford to spend a summer in Aspen working out, and who don't have free days just for working out? It turns out that exercise increases red blood cell count for people who struggle with health challenges as well as those who enjoy athletic prowess. Here are some examples.
- In one study, it was found that women who had rheumatoid arthritis had higher hemoglobin levels, higher red blood cell mass, and greater oxygen-carrying capacity of the blood after a program of exercise that lasted just eight weeks and that only required them to exercise at a moderate rate. There were not enough women enrolled in the study for the results to achieve statistical significance, but even with this study of just 17 women, the trend showed that the health of the blood improved with exercise despite arthritis. 
- It is not necessary to put out all the effort for running to increase red blood cell count. In another scientific study, men with obesity were found to have at least a short-term increase in red blood cell count and hematocrit (percentage of the blood that is red blood cells) immediately after they engaged in exercise. A greater increase in red blood cells took place after lower-intensity exercise compared to higher-intensity exercise, but with fewer breaks rather than more breaks. Slow, steady exercise did the most to trigger higher hemoglobin levels and higher red blood cell counts in obese men, and there is no reason to believe this would be different for anyone else. 
- Heat stress causes higher hematocrit and higher hemoglobin levels even without dehydration . You don't have to work out hard to experience changes in your blood by being exposed to heat, although dehydration, whether you work out hard or not, will accelerate the effect. Going to the sauna will contribute.
- Resistance exercises help people who are getting chemotherapy for lung cancer to maintain their white blood cell counts that help them fight opportunistic infections. The type of resistance exercise studied was done with elastic bands, but the study offered insights into resistance workouts in general.  And at least 16 different studies have found that aerobic exercise (which would include workouts such as walking, using a stationary bike, swimming, and so on) helps red store red blood cell counts lowered by chemotherapy, especially women getting chemotherapy for breast cancer .
Diet makes a difference in the way your blood cells respond to exercise
Zinc deficiencies interfere with the action of hemoglobin. If you get enough zinc, you will breathe better when you exercise.  This doesn't mean that if you get more and more zinc you will have more and more exercise capacity. It just means that you need to avoid zinc deficiency. Generally, if you take a zinc supplement and you don't notice an aftertaste, you probably need it. However, because zinc interferes with your body's ability to absorb copper, don't take more than 30 mg a day on a regular basis, and take 1 to 3 mg of copper along with your zinc supplement.
Exercisers who use whey powder tend to develop higher red blood cell counts and higher hemoglobin levels than those who do not. They also experience less fatigue after exercise.  Although they are specialty foods, black cumin seeds and lotus seeds also contain chemicals that help your body use the iron to make hemoglobin and possibly influence hormones involved in red blood cell production.
The important thing to remember is that almost any level of exercise helps your body to make the red blood cells it needs to carry oxygen through your bloodstream. The more you exercise, the more your body will use the iron in your diet and supplements . If you are not capable of high-intensity exercise, do not worry. That is OK, as slow and steady exercise is enough to stimulate your body to produce more of the red blood cells it needs.