Objectives
The present study investigated the effects of in-season enhanced-negative training (ENT) vs weight
training in change of direction (COD), sprinting and jumping ability, muscle mass and strength in
semi-professional soccer players.

Material and methods
Forty male soccer-players participated in the eight-week, 1d/w intervention consisting of 48 squat
repetitions for both ENT using a flywheel device (inertia=0.11 kg·m-2) or weight training (80%1-RM)
as control group (CON). Agility T-test, 20+20m shuttle, 10m and 30m sprint, squat jump (SJ) and
countermovement jump (CMJ), lean mass, quadriceps and hamstrings strength and the hamstringsto-
quadriceps ratio were measured.

Results
Time on agility T-test and 20+20m shuttle decreased in ENT (effect-size =-1.44, 95% CI -2.24/-0.68
and -0.75, -1.09/-0.42 respectively) but not in CON (-0.33, -0.87/0.19 and -0.13, -0.58/0.32). SJ and
CMJ height increased in both ENT (0.71, 0.45/0.97 and 0.65, 0.38/0.93) and CON (0.41, 0.23/0.60
and 0.36, 0.12/0.70). Overall, quadriceps and hamstrings strength increased in both ENT and CON
(0.38/0.79), but the hamstrings-to-quadriceps ratio increased in ENT (0.31, 0.22/0.40) but not in CON
(0.03, -0.18/0.24). Lean mass increased in both ENT (0.41, 0.26/0.57) and CON (0.29, 0.14/0.44).

Conclusions
The repeated eccentric actions performed in ENT may have led to improvements in braking ability, a
key-point in COD performance. Semi-professional soccer players may benefit from an in-season
ENT to enhance COD