In a 1990 study Houmard et al looked at detraining of experience endurance runners who were averaging 81km per week in training (~60km at ~75% VO2 max and 21km at ~95% VO2 max). Over a three-week period of detraining the athletes cut their volume by 70% to 24km, maintaining the intensity distribution with 17km at ~75% of VO2 max and 7km at ~90% VO2 max. The participants in the study had an increase in maximum heart rate (2.3%), and plasma volume decreased (-5.6%) during the period of reduced ...