The secondary outcomes are peak muscle force generated during gait assessed by the MSM, peak force measured during the isometric evaluation, inter-segmental coordination during gait assessed by 3D analysis, and functional tests.
Inter-segmental coordination during locomotion
Inter segmental coordination during gait will be analyzed using a 3-dimensional (3D) motion capture system (Motion Analysis Corporation, Santa Rosa, CA, USA, six cameras, Sampling Frequency 100 Hz) and two force plates (AMTI, Watertown, MA, USA, Sampling Frequency 1000 Hz). The trajectories of 24 markers placed on anatomical landmarks using the Helen Hayes marker set will be recorded and filtered using a fourth-order zero-lag Butter worth low-pass-filter with a 6 Hz cut off frequency.
3D Gait Analysis will be carried out during V1, V3 and V4. To limit inter-investigator variability, one operator in each centre will carry out all assessments. In addition, this operator will be in blinded to group allocation. Two conditions will be analysed: preferred and maximal walking speed. For each condition, eight trials will be recorded to ensure a minimum of ten gait cycles from both lower limbs. Boudarham et al. suggested that during 3D analysis, there is a phase of adaptation during which gait is unstable [
42]. They thus suggested kinematic and kinetic analysis should be based on three to nine gait trials in patients with hemiparesis.
OrthoTrack 6.5 software (Motion Analysis Corporation, Santa Rosa, CA, USA) will be used to calculate kinematic and kinetic parameters, using Euler rotations (Grood and Suntay method) for the kinematic parameters.
Spatio-temporal parameters will be calculated for both lower limbs, including gait velocity, cadence, step and stride length, step width, and the duration of the single support phase. Kinematic and kinetic parameters will be calculated for both lower limbs for each sub-phase of the gait cycle (initial double contact phase, single support phase, final double contact phase and swing phase). The main kinematic parameters are peak flexion, extension, peak abduction, adduction, valgus/varus and rotation as appropriate for the pelvis, hips, knees and ankles. Ground reaction force and peak joint moments of the hips, knees and ankles will be calculated in the three dimensions of space.
The activity of eight muscles will also be recorded using a surface EMG system (MA311, Motion Lab Systems, Baton rouge; band-pass 15-3000 Hz): rectus femoris (RF), vastus lateralis (VL), gluteus maximus (GMax), hamstring (HAM), biceps femoris (BF), soleus (SOL), medial gastrocnemius (MG), tibialis anterior (TA). Electrode placements will follow SENIAM recommendations [
43]. These muscles function in synergies to produce gait, therefore an analysis of muscle synergies will be performed. Evaluation of the coordination of lower limb segments during gait typically involves reducing all the degrees of freedom to a small number of patterns [
44] that reflect the underlying neural control of gait [
45]. To extract muscle synergies, we will use the model presented in Delis [
46]. We will use the associated sNM3F algorithm to obtain a space-by-time modular description of EMG patterns. According to that method, modularity is defined as “linear combinations of both spatial and temporal modules”. This model has been shown to unify and encompass most previous approaches and to yield a concise description of muscle patterns underlying the execution of various motor tasks. Muscle synergies will be extracted from the EMG recorded during the gait analysis (RF, VL, HAM, GAS and SOL) using spatial and temporal methods in order to evaluate changes in the pattern of muscle activity following BTX-A or placebo injection and the subsequent reduction (or not) of spasticity and force produced. The relationship between muscle force and type of synergy developed by patients will be then be evaluated.
Five functional tests will be used to evaluate the impact of any changes in intersegmental coordination on functional ability. These tests will be carried out by the blinded physiotherapist.
The Timed up and go test (TUG): This test consists of measuring the timed performance of rising from a chair, walking 3 m, turning and sitting again. The subject wears his/her usual shoes and may use his/her usual gait aid. The starting position is sitting with the back against the backrest of the chair, the arms resting on the chair arms and the gait aid within easy reach. Time begins when the subject’s back is no longer in contact with the chair back and stops when the subject is sitting once again with his/her back against the chair back.
The 6 min walk test (6MWT): Subjects will be asked to walk for 6 min and the distance covered will be measured. They may slow down or stop but must resume walking as soon as possible. A standardized sentence of encouragement will be used to inform the patient of the remaining time each minute. This test will be carried out in a 30 m long, unused corridor. A cone will be placed at each end around which the subject must turn [
47,
48].
Ten meter walk test (10 MWT): The time taken to walk 10 m at maximal velocity will be recorded. The patients will be asked to walk as fast as possible over a distance of 14 m. The first and last 2 m will not be counted in order to eliminate the phases of acceleration and deceleration. Subjects will wear their usual shoes and may use a gait aid. Three trials will be carried out and the average used for analysis [
49,
50].
Stairs test (ST): Subjects will be asked to ascend and descend a flight of 13 stairs (15 cm high) 3 times at maximal speed, and the mean will be used for analysis. The starting point will be a line 16 cm away from the first step. After each ascent or descent, the subject will be allowed to rest. Subjects can use the handrail but only for balance, and must not pull on it. The time will begin when the first foot leaves the ground and will stop when the last foot touches the ground [
51].
The berg balance scale (BBS) will be used to measure balance [
52].The BBS has been developed to measure static and dynamic equilibrium in adults to detect people at risk of fall. It can also be used to identify people who can walk unaided and to predict the difficulties some individuals may encounter in everyday activities. The BBS includes 14 tests that assess static balance and dynamic equilibrium as: unipodal support trunk rotation getting up and sitting.