vΔ50 Race Walking: High Energetic Cost, Rapid VO2max, and No Slow Component.

Background: Race walking, an Olympic discipline, produces an increase in energy cost and a change in the recruitment pattern of muscle fibres compared with running, yet the cardiorespiratory responses of elite race walkers to severe-intensity exercise remain poorly characterised. Objectives: (i) To determine whether exhaustive exercise performed at vΔ50 elicits VO2max in young elite race walkers, and (ii) to compare the temporal and metabolic profiles of this effort with those of similarly trained runners. Methods: Fourteen elite junior athletes (seven race walkers and seven runners) completed an incremental test to determine velocity at the lactate threshold (vLT), vVO2max, and VO2max, followed by a constant-velocity trial at individual vΔ50 performed to voluntary exhaustion on a 400 m track. Breath-by-breath VO2, heart rate, capillary blood lactate concentration, and time to exhaustion, time limit (Tlim) were measured. Results: At vΔ50 (≈94% vVO2max), the race walkers reached VO2max, with no detectable VO2 slow component (SC) in six of seven participants. In contrast, runners exhibited a significant SC (8 ± 3% of total VO2). The energy cost (EC) was 16% higher in race walking than in running (p < 0.01). Conclusions: In elite junior race walkers, it seems that vΔ50 reliably elicits VO2max primarily due to a high baseline oxygen cost rather than a progressive VO2 SC, contrasting with the kinetic response observed in running. These discipline-specific responses suggest that interval training in race walking should be prescribed using walking-specific thresholds. This study is preliminary, given the small sample size; further studies with larger cohorts are warranted.