Heart rate and oxygen consumption relationship changes following intense training

Seven male competitive runners (maximal oxygen consumption [VO_2max] 66.2 ± 3.6 ml^.kg^‐1‐min^‐1) participated in an evaluation of the effect of intense training on the relationships between heart rate (HR), VO₂, and running speed. To establish a baseline relationship, subjects twice performed four randomly ordered steady‐state runs at a constant grade of 2.5%, and one maximal graded exercise test, following days of moderate intensity training (approximately 80% of v"O_2max). After baseline determination, subjects trained at a high intensity (approximately 90 to 95% of VO_2max) for 2 consecutive days. Following the 2 high‐intensity training days, subjects repeated the steady‐state treadmill running and performed another maximal exercise test. After the intense training period, HR was significantly reduced for any given running speed (p < 0.05), with a mean reduction for the four running speeds of 154 ± 7 to 149 ± 7 beats/min. Maximal HR was also significantly reduced following the intense training from 193 ± 12 to 190 ± 9 beats/min (p < 0.05). Measurements of VO₂ were unaffected by the acute increase in training intensity. These results suggest that the relationship between HR and V0₂ is affected by increased training intensity. HR may, therefore, not be an accurate indicator of work intensity following high‐intensity efforts.

KEYWORDS :

• heart rate
• oxygen consumption
• training
• hypervolemia