Time-to-Fatigue During Incline Treadmill Running: Implications for Individualized Training Prescription

Uphill running has been touted as a key interval training tactic for distance runners despite few scientifically derived recommendations for individualized training prescription. To date, a majority of uphill training research has focused on shorter, faster training bouts; however, longer, slower bouts based on an individual's velocity at maximum oxygen consumption (Vmax) may prove more effective. One potential longer bout length may be associated with the time Vmax can be maintained (Tmax), an approach proven effective in level-grade interval training. Therefore, the purpose of this investigation included examining the Tmax, heart rate, and test-retest reliability of incline treadmill running (INC) on a 10% grade at 65, 70, 75, 80, and 85%Vmax compared with level-grade running at Vmax. Twelve moderately trained distance runners (age, 26.4 ± 4.8; body mass, 64.3 ± 12.9 kg; height, 171.2 ± 9.3 cm; and V̇O2max, 56.6 ± 7.6 ml·min⁻¹·kg⁻¹) completed 2 Tmax INC trials at each submaximal Vmax and a level-grade Tmax at Vmax. The dependent variables were Tmax, heart rate plateau (HR(Plateau)), and half-time to heart rate plateau (½HR(Plateau)) of each condition. Statistical significance was set to p ≤ 0.05. Student's t-test revealed no significant differences in Tmax, HR(Plateau), and ½HR(Plateau) between trials 1 and 2 at any INC condition. One-way analysis of variance revealed significant differences in (a) Tmax during INC at 75, 80, and 85%Vmax and level-grade at Vmax and (b) ½HR(Plateau) during INC at 80 and 85%Vmax and all other conditions. In conclusion, Tmax and heart rate dynamics during INC proved reliable, and simple regression analysis revealed ∼68%Vmax during INC yields the same level-grade Tmax at Vmax.