Purpose:This study aimed to compare biomechanical aspects of a novel “running” diagonal stride (DSRUN) with “conventional” diagonal stride(DSCONV) skiing techniques performed at high speed.Methods:Ten elite Italian male junior cross-country skiers skied on a treadmill at 10 km/h and at a 10° incline utilizing both variants of the diag-onal stride technique.The 3-dimensional kinematics of the body,poles,and roller skis;the force exerted through the poles and foot plantar surfa-ces;and the angular motion of the leg joints were determined.Results:Compared to DSCONV,DSRUN demonstrated shorter cycle times (1.05 ± 0.05 s vs.0.75 ± 0.03 s (mean ± SD),p ＜ 0.001) due to a shorter rolling phase (0.40 ± 0.04 s vs.0.09 ± 0.04 s,p ＜ 0.001);greater force applied perpendicularly to the roller skis when they had stopped rolling forward (413 ± 190 N vs.890 ± 170 N,p ＜ 0.001),with peak force being attained earlier;prolonged knee extension,with a greater range of motion during the roller ski-stop phase (28° ± 4° vs.16° ± 3°,p =0.00014);and more pronounced hip and knee flexion during most of the for-ward leg swing.The mechanical work performed against friction during rolling was significantly less with DSRUN than with DSCONV (0.04 ±0.01 J/m/kg vs.0.10 ± 0.02 J/m/kg,p ＜ 0.001).Conclusion:Our findings demonstrate that DSRUN is characterize by more rapid propulsion,earlier leg extension,and a greater range of motion of knee joint extension than DSCONV.Further investigations,preferably on snow,should reveal whether DSRUN results in higher acceleration and/or higher peak speed.