The purpose of this study was to evaluate the relationship between short (< or =60 s) and long duration (4-12 min) measures of upper body power (UBP) and mass start classical cross-country ski performance. Several experienced skiers (eight men, five women) completed three separate tests of UBP on a double poling ergometer: two tests of highest average power output for 10 s (UBP(10)) and 60 s (UBP(60)), and an incremental test to exhaustion to measure peak oxygen uptake (VO(2PEAK)) and peak power output (UBP(PEAK)). Lastly, subjects competed in a 10-km classical cross-country ski race from which race speed (RS) was computed. RS correlated highly with UBP(10) (r = 0.93; P < 0.05), UBP(60) (r = 0.92; P < 0.05), and UBP(PEAK) (r = 0.94; P < 0.05); the correlation was lower but still significant for VO(2PEAK) (r = 0.88; P < 0.05). These findings suggest that both short and long duration measures of UBP are important determinants of mass start classical ski race performance.