The aim of the study was to examine the effects of two different
training programs (high-intensity-training vs. continuous endurance
training) on aerobic power and body composition in recreationally
active men and women and to test whether or not participants
were able to complete a half marathon after the intervention
period. Thirty-four recreational endurance runners were
randomly assigned either to a Weekend-Group (WE, n = 17) or
an After-Work-Group (AW, n = 17) for a 12 week-intervention
period. WE weekly completed 2 h 30 min of continuous endurance
running composed of 2 sessions on the weekend. In contrast,
AW performed 4 30 min sessions of high intensity training
and an additional 30 min endurance run weekly, always after
work. During an exhaustive treadmill test aerobic power was
measured and heart rate was continuously recorded. Body composition
was assessed using bio-impedance. Following the intervention
period all subjects took part in a half-marathon. AW
significantly improved peak oxygen uptake (VO2 peak) from
36.8 ± 4.5 to 43.6 ± 6.5 [mL.min-1.kg-1], velocity at lactate
threshold (VLT) from 9.7 ± 2.2 to 11.7 ± 1.8 [km.h-1] and visceral
fat from 5.6 ± 2.2 to 4.7 ± 1.9 In WE VO2 peak significantly
increased from 38.8 ± 5.0 to 41.5 ± 6.0 [mL.min-1.kg-1], VLT
from 9.9 ± 1.3 to 11.2 ± 1.7 [km.h-1] and visceral fat was reduced
from 5.7 ± 2.1 to 5.4 ± 1.9 (p < 0.01). Only the improvements
of VO2 peak were significantly greater in AW compared
with WE (pre/post group interaction: F=15.4, p = 0.01, η2 =
0.36). Both groups completed a half marathon with no significant
differences in performance (p = 0.63). Short, intensive
endurance training sessions of about 30 min are effective in
improving aerobic fitness in recreationally active runners.