Biomechanical analysis of the "running" vs. "conventional" diagonal stride uphill techniques as performed by elite cross-country skiers

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 diagonal stride technique.The 3-dimensional kinematics of the body,poles,and roller skis;the force exerted through the poles and foot plantar surfaces;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°±40 vs.16°±3°,p=0.00014);and more pronounced hip and knee flexion during most of the forward 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.

Methodological Guidelines Designed to Improve the Quality of Research on Cross-Country Skiing

Cross-country(XC)ski races involve a variety of formats,two different techniques and tracks with highly variable topography and environmental conditions.In addition,XC skiing is a major component of both Nordic combined and biathlon competi-tions.Research in this area,both in the laboratory and field,encounters certain difficulties that may reduce the reliability and validity of the data obtained,as well as complicate comparisons between studies.Here,13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing,as well as on the biathlon and Nordic combined skiing.We consider biomechanical(kinematic,kinetic and neuromuscular)and physiological methodology(at the systemic and/or muscle level),providing recommendations for standardization/control of the experimental setup.We describe the types of measuring equipment and technology that are most suitable in this context.Moreover,we also deal with certain aspects of nomenclature of the classical and skating sub-techniques.In addition to enhancing the quality of stud-ies on XC skiing,Nordic combined and biathlon,our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.