Heart rate response to a marathon cross-country skiing race : a case study

The aim of this study was to assess the exercise intensity during a ski marathon race by monitoring the heart rate (HR) of a well-trained male amateur skier taking part in La Sgambeda 2012 (42 km long). The race consisted of a preliminary short lap of 3.5 km and two almost identical laps of 19 and 19.5 km, respectively. The subject’s resting and maximal heart rates (HRrest and HRmax) were 60 and 180 beats/min, respectively. During the race, HR and altitude were recorded every 1 s using a HR monitor with GPS system. To describe the exercise intensity profile, three reference HRs were selected. The reference HRs were calculated from the ‘‘Karvonen formula’’ by multiplying the HR reserve (HRR; HRR = HRmax-HRrest) by the factors 0.5, 0.7, 0.9 and adding these values to HRrest. The HR profile was classified into four levels of exercise intensity. The skier performed the race in 1 h 55 min 40 s, with an HRmean of 160 beats/min (89 % of HRmax and 83 % of HRR). Nearly the entire race (96.6 %) was performed at an intensity between 70 and 90 % of HRR. The HRmean during the 2nd lap was slightly lower as compared to the HRmean during the 1st lap (from 162 ± 4 to 160 ± 4 beats/min, p.001). This study provided a detailed description of the HR response to a marathon cross-country skiing race. It showed that such race was performed at high intensity throughout the duration of the event, thus requiring high aerobic power.