Hill fartlek- Mixed hill running be used to improve running economy and boost an athlete's VO2 max. During most of the run, the athlete's heart rate should be close to 85% of maximum (85% of maximum heart rate matches up with 76% VO2 max). When doing long term the athlete’s body should experience increased lung volume and when doing short term an increase in heart rate. The reason the athletes lung volume increases is due to the demands of the athlete’s body during exertion, their breathing becomes deeper and more rapid, which will be delivering more oxygen to your bloodstream to meet the increased needs of their heart and muscle cells. A by-product of respiration, carbon dioxide and this is released during exhale. The reason heart rate increases
