Many endurance athletes and coaches fear a decrement in physical conditioning and performance if training is reduced for several days or longer. This is largely unfounded. Maximal exercise measures (VO2max, maximal heart rate, maximal speed or workload) are maintained for 10 to 28 days with reductions in weekly training volume of up to 70 to 80%. Blood measures (creatine kinase, haemoglobin, haematocrit, blood volume) change positively or are maintained with 5 to 21 days of reduced training, as are glycogen storage and muscle oxidative capacities. Submaximal or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that or improved with a 70 to 90% reduction in weekly volume over 6 to 21 days, provided that exercise frequency is reduced by no more than 20%. Athletic performance is improved or maintained with a 60 to 90% reduction in weekly training volume during a 6 to 21 day reduced training period, primarily due to an enhanced ability to exert muscular power. These findings suggest that endurance athletes should not refrain from reduced training prior to competition in an effort to improve performance, or for recovery from periods of intense training, injury, or staleness.