The purpose of this study was to examine the effects of speed on the stretc
h-shortening cycle (SSC behavior during roller ski skating. Ten highly skil
led male cross-country skiers roller skied at 4.56, 5.33 m . s(-1) and maxi
mal speed using the V2-alternate technique on a flat terrain. Knee and ankl
e joint kinematics, and EMG of the vastus lateralis NL) and gastrocnemius l
ateralis (GL) muscles were recorded during the last 40 s of each bout of ro
ller skiing. Maximal speed was associated with increases in cycle rate comb
ined with decreases in cycle length. For VL, no significant differences wer
e observed for the integrated EMG eccentric-to-concentric ratio (iEMG Ecc/C
onc) and for the stretching velocity over the range of speeds. For GL, stre
tching velocity and iEMG Ecc/Conc were significantly greater at maximal spe
ed. The analysis of GL EMG activity suggests that speed improved GL stiffne
ss so that more elastic energy was stored, a better force transmission occu
rred, and coupling time decreased. These findings suggest that the efficien
cy of roller ski skating locomotion may be increased with speed through a b
etter use of the stretch-shortening cycle pattern in the ankle extensors.