Effects of Aerodynamic Drag and Drafting on Propulsive Force and Oxygen Consumption in Double Poling Cross-Country Skiing

PURPOSE: This study aimed to investigate the effects of aerodynamic drag and drafting on propulsive force (F(PROP)), drag area (C(D)A), oxygen cost (V˙O(2)), metabolic rate (E˙), and heart rate (HR) during roller skiing on a treadmill in a wind tunnel using the double poling technique. A secondary aim was to investigate the effects of wind versus no-wind test conditions on the same physiological parameters. METHODS: Ten subjects of each gender participated in the experiments. One pair of skiers of the same gender roller skied simultaneously in line with the air flow; the distance between the skiers was ~2.05 m. Each pair was tested as follows: I) with wind, leading; II) with wind, drafting; and III) without wind. The treadmill inclination was 0° throughout the tests. For the wind conditions, the air velocity was similar to the treadmill belt speed: 3 to 7 m·s(−1) for men and 3 to 6 m·s(−1) for women. RESULTS: Drafting resulted in significantly (P < 0.05) lower F(PROP,)C(D)A, V˙O(2), and E˙, compared with leading, for both genders at racing speed but not at lower speeds, whereas HR was only affected for the male skiers at racing speed. The test without wind resulted in significantly lower F(PROP), V˙O(2), and E˙ at all tested speeds compared with the tests with wind present, whereas HR was lower only at higher speeds. CONCLUSIONS: At racing speed, but not at lower speeds, the positive effects of drafting behind a skier during double poling were obvious and resulted in a lower F(PROP), C(D)A, V˙O(2), E˙, and HR. Tests without wind present put even lower demands on the skiers’ physiology, which was also evident at lower speeds.