Heart rate variability to assess ventilatory threshold in ski-mountaineering.

The capacity to predict the heart rate (HR) and speed at the first (VT1) and second (VT2) ventilatory thresholds was evaluated during an incremental ski-mountaineering test using heart rate variability (HRV). Nine skiers performed a field test to exhaustion on an alpine skiing track. VT1 and VT2 were individually determined by visual analysis from gas exchanges (VT1V and VT2V) and time-varying spectral HRV analysis (VT1fH, VT2fH and VT2H). VT1 could not be determined with the HRV methods used. On the contrary, the VT2 was determined in all skiers. No significant difference between HR and speed at VT2H and VT2V was observed (174.3 ± 5.6 vs. 174.3 ± 5.3 bpm, and 6.3 ± 0.9 and 6.3 ± 0.9 km h(-1), respectively). Strong correlations were obtained for HR (r = 0.91) and speed (r = 0.92) at VT2H and VT2V with small limits of agreement (±3.6 bpm for HR). Our results indicated that HRV enables determination of HR and speed at VT2 during a specific ski-mountaineering incremental test. These findings provide practical applications for skiers in order to evaluate and control specific training loads, at least when referring to VT2.