A Comparison of Drop and Depth Jumps in Eccentric and Concentric Phases

Background: The shift of muscles from an eccentric to a concentric phase could be an important factor in the variation of muscle engagement during different types of jumps, such as drop (DJ1) and depth jumps (DJ2).

Aim: The purpose of the study was to investigate the differences during DJ1 and DJ2 in lower limbs for verifyingied the possible differences in muscle recruitment that can affect the emphasis of neuromuscular activation in eccentric and concentric contractions.

Methods: The data were acquired in 14 elite U17 football players (mass 64.36kg±4.5, height 177.36cm±4.5) with GPS-IMU Spinitalia v2 (acquired at 100 Hz) and EMG Myontec M-Body 2 (resampled at 100 Hz) for quadriceps, hamstrings and gluteus at different drop heights (40, 50, 60, 70cm in bipodal jumps, 20 and 40cm for both monopodal jumps).

Results: The comparison of IEMG in bipodals DJ1 and DJ2 shows significant differences only in concentric phases, respectively for falls from 40cm p=0.00 and d=0.84; from 50cm p=0.00 and d=0.67; from 60cm p=0.00 and d=0.50; and from 70cm p=0.00 and d=1.25. The monopodals IEMG (always evaluating only the contact leg for monopodal jumps) in concentric phases results for the left monopodal from 20cm p=0.07 and d=0.71; right monopodal from 20cm p=0.02 and d=0.95; from 40cm the left monopodal p=0.02 and d=0.93; from 40cm the right monopodal p=0.01 and d=1.01. When comparing the differences between DJ1 and DJ2 in relation to the peak value obtained on RBJs (Rebound Jump Multiples) as normalization for EMG, differences were also found in all bipodals eccentric phases, respectively for falls from 40cm p=0.00 and d=1.42; from 50cm p=0.00 and d=1.76; from 60cm p=0.00 and d=1.45; from 70cm p=0.00 and d=1.49; and for eccentric phases of monopodal left from 20cm result p=0.00 and d=1.43; right monopodal from 20cm p=0.00 and d=1.77; from 40cm the left monopodal p=0.05 and d=0.77; from 40cm the right monopodal p=0.43 and d=0.30.

Discussion: The evaluation of the electromyographic effort over time (IEMG) seems to vary purely in the concentric phases in these two different types of jumps, presumably due to the change in the temporal expression of the motor action, while in a more qualitative evaluation such as the electromyographic effort in relation to the RBJs, the eccentric phases also seem to vary with the change in the executive technique. We could thus summarize that the change in eccentric phases seems more qualitative and that of concentric phases more quantitative.

Conclusions: During DJ1 and DJ2 a considerable variation was found in muscle commitment that can affect the emphasis of neuromuscular activation towards eccentric or concentric contractions between these two different jump modes.

Keywords: drop jump; depth jump; eccentric phase; concentric phase; EMG