Exercise Intensity During Cross-Country Skiing Described by Oxygen Demands in Flat and Uphill Terrain

Abstract

Purpose: In this study wearable global navigation satellite system units were used on athletes to investigate pacing patterns by describing exercise intensities in flat and uphill terrain during a simulated cross-country ski race.Methods: Eight well-trained male skiers (age: 23.0 ± 4.8 years, height: 183.8 ± 6.8 cm, weight: 77.1 ± 6.1 kg, VO2peak: 73 ± 5 mL⋅kg-1⋅min-1) completed a 13.5-km individual time trial outdoors and a standardized indoor treadmill protocol on roller skis. Positional data were recorded during the time trial using a differential global navigation satellite system to calculate external workloads in flat and uphill terrain. From treadmill tests, the individual relationships between oxygen consumption and external workload in flat (1°) and uphill (8°) terrain were determined, in addition to VO2peak and the maximal accumulated O2-deficit. To estimate the exercise intensity in the time trial, the O2-demand in two different flat and five different uphill sections was calculated by extrapolation of individual O2-consumption/workload ratios.Results: There was a significant interaction between section and average O2-demands, with higher O2-demands in the uphill sections (110–160% of VO2peak) than in the flat sections (≤100% of VO2peak) (p < 0.01). The maximal accumulated O2-deficit associated with uphill treadmill roller skiing was significantly higher compared to flat (6.2 ± 0.5 vs. 4.6 ± 0.5 L, p < 0.01), while no significant difference was found in VO2peak.Conclusion: Cross-country (XC) skiers repeatedly applied exercise intensities exceeding their maximal aerobic power. ΣO2-deficits were higher during uphill skiing compared to flat which has implications for the duration and magnitude of supramaximal work rates that can be applied in different types of terrain.

The Interval-Based Physiological and Mechanical Demands of Cross-Country Ski Training

“…Many previous studies have shown that higher work rates are obtained on uphill terrain in XC skiing during actual and simulated competitions. 4,[6][7][8][9][10][11][12]14,16 However, this study provides additional information about XC skiers' ability to generate WRmax in flat and uphill skating on snow, and the percentage of WRmax achieved in both terrains during LIT, MIT and HIT. Specifically, the skiers reached ~595 W (7.75 W•kg -1 ) with the G2-skating technique on uphill terrain, which is 80% greater than the ~326 W (4.23 W•kg -1 ) performed with the G3-skating technique on the flat.…”

“…This has previously been reported by Bolger et al 4 in world-class skiers during distance races across varying terrain, and although this effect is clearly greater at high intensities, we here show that it is present during all the endurance training intensities. The greater effect of the delayed HR response during HIT is due to the fact that work rates exerted in the uphill terrain drives the intensity above maximal oxygen uptake 6,9,11 and causes oxygen deficit, which eventually leads to an additionally increase in HR in the subsequent terrain. This gives less opportunity for recovery, resulting in a relatively higher and more stable HR throughout the course during HIT.…”

“…As expected, the relative contribution from work rate against air drag increased slightly with higher speed in the uphill terrain, and logically follows the pattern found in previous research. 6,9 The skier's average HR for the total course and in all terrains increased with intensity (all P < .05; Figure 3 and Table 2). The difference in average HR for the total course was higher for MIT versus LIT (10.3 [4.8] %HRpeak) compared to HIT versus MIT (3.3 [1.6] %HRpeak) (all P < .004; Figure 3).…”

“…5 Due to the varying terrain in XC skiing, the competitions are interval-based with increased generation of external work rate and metabolic intensity uphill, and reduced effort in the downhill terrain. 1,[4][5][6][7][8][9][10][11][12][13][14][15][16] Currently, these factors have only been examined in a performance setting at high-intensity (HIT), and no previous study has investigated whether the same occurs while training at low-(LIT) and moderate-intensity (MIT) that reflects around 80% of a XC skier's overall training. [17][18][19][20][21][22][23][24][25] Heart rate (HR) is commonly normalized to its maximal value (HRmax) to reflect an individual's internal metabolic intensity/effort during training and competition.…”

“…[17][18][19][20][21][22][23][24][25] Heart rate (HR) is commonly normalized to its maximal value (HRmax) to reflect an individual's internal metabolic intensity/effort during training and competition. 1,4,9,13,15,16 However, the corresponding utilization of the maximal external work rate (WRmax) has not yet been addressed in XC skiing, which is more complex since WRmax varies with the changes in external condition. Such information would go beyond previous analyses of speed profiles 1,4,5 that is highly influenced by the variations in opposing forces from snow-ski friction, air drag and gravity across different terrains.…”