Multi-exercise devices like the kBox and kPulley have huge benefits in terms of versatility in various settings, whereas single-exercise devices are beneficial when you need to focus on a specific muscle group. The LegExx primarily targets the quadriceps femoris muscles.
For healthy users (injury-free), the general benefit with a leg extension machine is that it allows 100% muscle stimulation by maximizing hypertrophy and strength gains in the quadriceps, without overcompensating with other muscles (e.g. glutes in squats). While for injured or low mobility users (e.g. in rehab for ACL or patellar tendinopathies), the main benefit involves gaining strength in the quadriceps without having to worry about posture or complex poliarticular movements, such as the squat.
The LegExx offers full stimulation over the whole range of motion and in all parts of the quadriceps femoris, both concentrically and eccentrically, thanks to the unlimited and variable resistance of the flywheel (XL or L by default, more can be purchased separately). Moreover it is designed to allow users to easily overload themselves in the eccentric phase by simply pulling on a handle without any need for external help.
The phone holder on the LegExx will allow users to comfortably get instant feedback as they train with the kMeter II feedback system.
And lastly the mobility of the LegExx makes it unique in comparison with other leg extension alternatives due to its practical wheels and absence of a weight stack. This makes the machine suitable for flexible facilities, circuit training, and more.
Minimal assembly (by default), Unassembled (detailed guide available)
100 x 139 cm (39.4 x 54.7 in)
80 x 108 cm (31.5 x 32.5 in)
110 cm (43.3 in)
95 kg (210 lbs)
|Maximum weight allowed|
350 kg (772 lbs)
|Inertia range (standard)|
XS, 0.005 kgm² – XL, 0.280 kgm²
Built-in kMeter II feedback system
XS (0.005 kgm²), S (0.010 kgm²), M (0.025 kgm²), L (0.050 kgm²), XL (0.070 kgm²) – recommended
kBox4 Pro, kBox4 Lite, kPulley, LegExx
LegExx, kPulley, kBox4 Active and all kBox4 Lite & kBox4 Pro devices produced since May 2018
10000 Hz (155 revolutions/second)
L – 0.050 kgm², XL – 0.070 kgm²
kBox4 Pro, kBox4 Lite, kBox4 Active, kPulley, LegExx
Standard, Color Coded