With the new lockdown in place, it is being suggested to wear a mask while exercising when you can’t social distance, even outside. Some worry that it is not safe while others just feel it is difficult. To begin with, it is perfectly safe, and knowing this might help you overcome the difficulty. The difficulty comes from rising CO2 levels and the perception that you need more oxygen. On the most basic of levels, breathing is about the exchange of gases: oxygen, and CO2. Most people perceive that to breathe comfortably they need more oxygen, as in they have run hard to the finish line, are gasping for air and they think more oxygen will make breathing easier. In fact, our breathing rate is regulated by accumulating CO2. If you hold your breath, your body continues to use oxygen to feed the cells, and the by-product, CO2 starts to accumulate. This accumulation triggers your breathing rate to increase, for you to open your mouth and expel the accumulated CO2. CO2 is tolerated by the body in varying degrees. If you live a stressful, running from a lion life and over breathe, your CO2 tolerance is low. If you breathe diagrammatically, through your nose, and live a rest and digest life your CO2 tolerance is higher. The level of tolerance can be adjusted with practice. Think swimming across a pool in one breath; at the beginning of the summer, you make it halfway across and by the end of the summer you can swim straight across. Your level of tolerance to accumulating CO2 has increased. So, let’s talk about running. When you transition from walking to running, your body uses up the supplied oxygen very quickly which causes a large spike in CO2 which causes an increased breathing rate to expel it. Once your heart rate catches up to the demand and you’ve expelled excess CO2 your breathing rate will come down. Your tolerance level determines how quickly your breathing rate increases and how much effort it takes. Like swimming, you can increase this tolerance level by nasal breathing while you run at easy efforts. When you put on a mask to run it will restrict this process making it feel harder and like you need more oxygen. I urge you to resist the impulse to concentrate on the inhale (oxygen) and instead purposefully concentrate on the exhale (blowing off CO2), this will also aid in diaphragmatic breathing. Slow down your effort so you can control the process better and when feeling like you need more oxygen try hyperventilating (rapid breaths) which is about decreasing CO2 levels. The first couple of runs will seem difficult and you will feel like you must go super slow but both things will make your running easier and/or faster in the long haul by improving your base and raising your CO2 tolerance level.