Is possible an eccentric overload in a rotary inertia device? Comparison of force profile in a cylinder-shaped and a cone-shaped axis devices

Inertial flywheel knee- and hip-dominant hamstring strength exercises in professional soccer players: Muscle use and velocity-based (mechanical) eccentric overload

“…line with Nunez et al [31], after analyzing all repetitions during the training session showed less mean (-29% to -35%, Table 1) and peak (-6% to -17%, Table 1) power during the ECC phase in comparison with the CON phase. Mainly, this was due to the substantial and excessive disparity in time between the phases (Fig 4), with time in ECC vs CON ratios increasing gradually as the sets were executed (from +42% to +61%).…”

“…kinematic data measuring the velocity with a lineal encoder and force with a strain gauge during all-out knee flexions in a flywheel leg-curl, showing that this flywheel device offered eccentric overload to experienced athletes in peak force or velocity, but not in mean force and mean velocity. In the same line, Núñez et al [31] did not obtain any force or velocity eccentric overload during the squat exercise using two different inertial devices (conic-pulley and Yo-Yo flywheel). When compared with free weights, Núñez et al [32] reported, in experienced rugby players, a substantially greater eccentric overload and augmented metabolic demands with these devices [32].…”

“…Training session data from our study showed that for inexperienced professional soccer players there was no eccentric overload (defined as greater load during the ECC phase vs the CON phase) during LC exercise. While flywheel devices are a very convenient technology for emphasizing more forceful actions in the ECC--CON transition phase, it is unclear whether such devices can offer eccentric overload [31]. A previous study suggests that using the inertia provided by a rotating flywheel to provide resistance in leg-curl exercise may enable the production of eccentric overload [25].…”

“…When compared with free weights, Núñez et al [32] reported, in experienced rugby players, a substantially greater eccentric overload and augmented metabolic demands with these devices [32]. Thus, despite that it is likely that inertial devices can generate augmented eccentric overloads compared with free weights and other traditional devices [32], it is not clear what magnitude of eccentric overload can be generated in relation to the concentric phase with these devices [25,31].…”

Strength Conditioning Program to Prevent Adductor Muscle Strains in Football: Does it Really Help Professional Football Players?

“…Adduction (ADD) and abduction (ABD) power were measured using a rotatory inertial device (conic-pulley; Twister Pulley: Element Sport, Cádiz, Spain; speed/force ratio level 1 out of 3). These systems provide a source of linear resistance via a tether wrapped around a vertical cone-shaped shaft [ 22 ]. The kinetic energy from the acceleration phase of the exercise is transferred to the deceleration phase, where an equal impulse is necessary to halt the rotation of the moment of inertia [ 23 ].…”