## 1 Introduction  
The stroke is a dramatic vascular event that causes death in 20% of cases and chronic disability in most survivors [1]. Spastic hemiparesis is one of the most disabling consequences of a stroke. Muscle weakness due to disruption of corticospinal pathways occurs immediately [2], while spasticity appears later as a result of plastic neuronal changes within the central nervous system after the initial injury [3].  
Weakness and spasticity are essential diagnostic and prognostic elements for delineating effective rehabilitation strategies. The most commonly used techniques for measuring strength in clinical practices are the Medical Research Council (MRC) scale and the hand-held dynamometer (HHD). These techniques have limitations, since they are semi-subjective and not able to guarantee an isometric contraction respectively; moreover, the lying or sitting postures used during these tests do not correspond to the walking posture [4; 5].  
The Modified Ashworth Scale (MAS) and the Modified Tardieu Scale (MTS) are the most widely utilized instruments to estimate spasticity. Their application is limited by the operator's experience and the difficulty of controlling the movement's speed during the test [6; 7].  
Isokinetic dynamometry represents a quantitative approach for measuring strength. However, its use is not yet widespread due to high cost [8; 9].  
Lokomat (Hocoma, Volketswil, Switzerland) is the most frequently used walking robotic aid in rehabilitation [10]. This aid supports the weight of patients and assists hip and knee effort by means of four servomotors. L-FORCE (lower limb-force) [11; 12] is a Lokomat tool that measures torque at the hip and the knee joints during maximal voluntary isometric torque. L-STIFF (lower limb-stiff) [12; 13] is a Lokomat tool that measures how resistive torque changes in the hip and knee during both flexion and extension for predefined passive movements, by moving the joint at a constant velocity. L-ROM (lower limb-range of motion) [12] is a Lokomat tool that measures the passive range of motion (ROM) of the hip and knee without support of the Lokomat drives. Therefore, L-FORCE, L-STIFF and L-ROM allow follow-up of joint torque, stiffness and joint range of motion during a Lokomat training session, respectively [10]. Since weakness and spasticity are directly related to joint torque and stiffness, Lokomat can be considered a suitable measurement tool for weakness and spasticity estimation in rehabilitation processes.  
The efficacy of Lokomat on motor recovery in patients suffering stroke is well known [14; 15]. Regarding L-FORCE, L-STIFF and L-ROM tools of Lokomat, they have been addressed in different studies. Particularly, in studies related to children with cerebral palsy. In [16] the authors found that L-STIFF is a feasible tool to assess the stiffness in children with cerebral palsy. Likewise, in [13] the authors found that the L-STIFF is a promising tool to assess spasticity in children with cerebral palsy in a standing position. Regarding subacute stroke, some works have addressed the effectiveness of the Lokomat such as the studies in [17; 18; 19]. However, in [17; 18; 19], L-FORCE, L-STIFF and L-ROM tools were not addressed for subacute stroke. Therefore, a study related to joint torque, stiffness, and joint ROM obtained using L-FORCE, L-STIFF and L-ROM tools of Lokomat, particularly in the subacute phase of stroke, is interesting. The purpose of this retrospective observational study is to assess the changes of joint torque, ROM, and stiffness that were estimated with Lokomat tools, namely L-FORCE, L-ROM and L-STIFF, for paretic and non-paretic lower limbs in the subacute phase of stroke, assuming that the tools were able to measure these changes. Data obtained using L-Force, L-Stiff and L-ROM tools for stroke patients in subacute phase were compared between paretic and non-paretic sides before and after a rehabilitation treatment with Lokomat.