Effects of between-set interventions on neuromuscular function during isokinetic maximal concentric contractions of the knee extensors.

The presents study investigated the effects of between-set interventions on neuromuscular function of the knee extensors during six sets of 10 isokinetic (120°·s(-1)) maximal concentric contractions separated by three minutes. Twelve healthy men (age: 23.9 ± 2.4 yrs) were tested for four different between-set recovery conditions applied during two minutes: passive recovery, active recovery (cycling), electromyostimulation and stretching, in a randomized, crossover design. Before, during and at the end of the isokinetic session, torque and thigh muscles electromyographic activity were measured during maximal voluntary contractions and electrically-evoked doublets. Activation level was calculated using the twitch interpolation technique. While quadriceps electromyographic activity and activation level were significantly decreased at the end of the isokinetic session (-5.5 ± 14.2 % and -2.7 ± 4.8 %; p < 0.05), significant decreases in maximal voluntary contractions and doublets were observed after the third set (respectively -0.8 ± 12.1% and -5.9 ± 9.9%; p < 0.05). Whatever the recovery modality applied, torque was back to initial values after each recovery period. The present results showed that fatigue appeared progressively during the isokinetic session with peripheral alterations occurring first followed by central ones. Recovery interventions between sets did not modify fatigue time course as compared with passive recovery. It appears that the interval between sets (3 min) was long enough to provide recovery regardless of the interventions. Key pointsAllowing three minutes of recovery between sets of 10 maximal concentric contractions would help the subjects to recover from the peripheral fatigue induced by each set and therefore to start each new set with a high intensity.During this type of session, with three minutes between sets, passive recovery is sufficient; there is no need to apply complicated recovery interventions.