Time to Exhaustion During Severe Intensity Running: Response Following a Single Bout of Interval Training

The primary aim of this study was to examine any change in performance caused by a fatiguing interval training session (TS). A secondary aim of this study was to examine the change in oxygen uptake ((V) over dot O-2) during moderate and severe intensity running, and the relationship with the change in performance. Seven male runners [mean age 24 (SD 6)years, height 1.79 (SD 0.06) m, body mass 67.9 (SD 7.6) kg, maximal oxygen uptake ((V) over dot O-2max) 4.14 (SD 0.49)l . min(-1)] were studied. The (V) over dot O-2 during moderate and severe intensity running and running performance were studied immediately prior to, 1 h following, and 72 h following TS. The TS was performed on a treadmill, and consisted of six bouts of 800 m at 1 km . h(-1) below the velocity at (V) over dot O-2max (v((V) over dot O2max)) with 3-min rest intervals. Performance was also assessed at 1 km . h(-1) below v((V) over dot O2max), in the form of time to exhaustion (t(lim)). The (V) over dot O-2 and heart rate (f(c)) were assessed both during the severe intensity performance trial, and the moderate intensity run at 50% v((V) over dot O2max). Whilst a significant change was observed in running performance and the (V) over dot O-2 during both moderate and severe intensity running prior to and following TS, no relationship was observed between the magnitude of change in these variables. At 1 h following TS, t(lim) had decreased by 24%, (V) over dot O-2 during moderate intensity running had increased by 2%, and the difference in (V) over dot O-2 between 2 min 45 s and the end of severe intensity running had increased by 91% compared with values recorded prior to TS. At 1 h following TS, f(c) had also increased significantly during moderate intensity running by 5% compared to the value recorded prior to TS. These findings demonstrated that TS resulted in a reduction in performance, and that the relationship between running performance and (V) over dot O-2 during running may be altered under conditions of prolonged fatigue