Abstract
This study used functional magnetic resonance imaging (fMRI) to compare individual
muscle use in exercises aimed at preventing hamstring injuries. Thirty-six professional
soccer players were randomized into 4 groups, each performing either Nordic hamstring,
flywheel leg curl, Russian belt or conic-pulley exercise. MRIs were performed before
and immediately after a bout of 4 sets of 8 repetitions. Pre-post exercise differences
in contrast shift (T2) were analyzed for the long (BFLh) and short head (BFSh) of biceps femoris, semitendinosus
(ST), semimembranosus (SM) and gracilis (GR) muscles. Flywheel leg curl increased
(P<0.001) T2 of GR (95%), ST (65%), BFSh (51%) and BFLh (14%). After the Nordic hamstring, GR
(39%), ST (16%) and BFSh (14%) showed increased T2 (P<0.001). Russian belt and conic-pulley exercise produced subtle (P<0.02) T2 increases of ST (9 and 6%, respectively) and BFLh (7 and 6%, respectively). Russian
belt increased T2 of SM (7%). Among exercises examined, flywheel leg curl showed the most substantial
hamstring and GR muscle use. However, no single exercise executed was able to increase
T2 of all hamstring and synergist muscles analyzed. It is therefore suggested that multiple
exercises must be carried out to bring in, and fully activate all knee flexors and
hip extensors.
Key words
eccentric overload - football - gracilis - functional magnetic resonance imaging -
iso-inertial exercise