The goal of this study is to obtain the maximum voluntary torques of the lower-limb joints and to monitor oxygen level in the main lower-limb muscles. This will be done for three joints: i.e. the hip, knee and ankle joint and NIRS sensors will be placed on the biceps femoris, rectus femoris and gastrocnemius muscle. For the hip and knee, the maximum torque will be determined both in exertion direction and flexion direction. For the ankle, both plantarflexion and dorsiflexion will be considered. For each of these directions, the maximum joint torque will be defined for different specific joint angles and joint velocities (see procedure). For every joint and for the whole protocol for the torques measurement campaign, the different muscle of interest will be monitored with the NIRS, i.e. hip is associated with hamstring contraction, knee is associated with thigh contraction and ankle is associated with calf contraction. With these discrete points, an algorithm will be used to obtain a complete plot of the maximum torque in function of both joint angle and joint velocities. Comparing these plots between for example stroke and healthy individuals can help us understand what level of assistance stroke patients require. Comparison in oxygen level between healthy individuals and impairments population of stroke and sarcopenia patients can also help us investigate how oxygen is used depending on the population.

Post stroke patients:

• Must be 18+ years old
• Must be three months or more after stroke diagnosis
• Have difficulties with gait (FAC level 3-4)

Sarcopenia patients:

• Must be 65+ years old
• Not be able to perform five chair sit to stands within 15 seconds
• Grip strength of less than 27 kg for men and less than 16 kg for females
• Have difficulties with gait (SPPB ≤ 8)

Healthy participants:

• No physical injuries that limits the torque production in lower-limb joints