Electromyographic activity, force and anaerobic energy production in sprint running : with special reference to different constant speeds ranging from submaximal to supramaximal

Abstract

Electromyographic (EMG) act1v1ty, force and anaerobic energy production were investigated in male and female sprinters (n=41) running at different constant speeds ranging from submaximal to supramaximal. Supramaximal running was performed by a towing system. Cinematographic analysis showed that both stride length (SL) and stride rate (SR) increased (p<0.05-0.001) with increasing running speed and the difference (p<0.001) between men and women in maximal velocity was accompanied by a significant (p<0.01) difference in SL. In supramaximal running the increase in velocity was associated with an increase (p<0.05-0.001) in either SL or SR. Neural activation (IEMG) of the leg muscles measured with a telemetric system increased (p<0.05-0.001) with increasing running speed, being greater (p<0.001) in the braking phase than in the propulsion phase. Preactivity of the five leg muscles increased and correlated positively and significantly (p<0.01) with the average resultant force in the braking phase with increasing speed. Higher running speed was accompanied by increases (p<0.05-0.001) in the average resultant force during both contact phases except during the propulsion phase of the highest test speeds. Force platform recordings also showed that maximal and average forces in the braking phase were greater (p<0.01-0.001) during supramaximal than during maximal running. Blood lactate and oxygen debt were significantly (p<0.05-0.001) greater for exercise and recovery following the maximal rather than the supramaximal runs, showing lower anaerobic energy production in supramaximal sprinting. On the basis of correlational analysis, it was further concluded that in supramaximal running with a horizontal towing system it is possible to run at a higher SR than in normal maximal running. Preactivity increases stiffness in leg muscles, which is needed to resist high impacts during the very first stages of contact. Average net resultant contact force as a specific force indicator is greater in men and is primarily related to SL; the values for this indicator explain the differences in maximal running velocity between men and women.