seems to be more beneficial in individuals following stroke and spinal cord injury (SCI) with respect to other neurological disorders [5]. Some studies reported a marked improvement in lower limb motor functions and walking abilities in incomplete SCI subjects with the use of electromechanical systems [6; 7; 8; 9] and positive effects in the reorganization of spinal locomotor neuronal networks [10]. However, other studies [11; 12] found that robot-assisted training does not determine better outcomes than traditional rehabilitation. Thus, while undoubtedly powered exoskeletons can provide non-ambulatory individuals with the ability to walk at modest speed [13], the literature highlights conflicting results for the training potential of these devices, and there is no compelling evidence that robot-assisted gait re-education improves walking function more than other rehabilitative strategies [8; 9; 14; 15; 16; 17]. Moreover, although exoskeletons are already used as an alternative option to traditional therapy, there is still a lack of knowledge regarding their specific effects on the user locomotor function. We expect that the guidance they provide would restore muscle coordination patterns similar to the physiological human walking. However, little research has been conducted in this direction, and the few studies confirmed the necessity to further investigate this topic [18; 19; 20; 21], suggesting that either the assistive external forces provided during walking [18] or the structure of the device itself [22] can affect normal muscle activations as well as kinetic and kinematic patterns during locomotion. To systematically investigate all these aspects is crucial and at the same time difficult. There are several solutions available for the mechanical structure of the exoskeletons; it is possible to use them with different aids and under different assistive modalities, e.g., unilateral versus bilateral assistance, or maximum assistance versus adaptive assistance based on users' performance. To the best of our knowledge, these aspects were not deeply investigated with an integrated approach aiming at accounting how each of them influences the overground walking patterns. This study aimed at filling this gap and had two main objectives. The first was to examine whether and how different assistive modalities influence the muscle patterns during walking. The second was to compare the muscle activations when walking overground with and without an exoskeleton and verify whether the observed differences are due to the mechanical structure of the exoskeleton, the walking aids, or the assistive forces provided by the device. Our first hypothesis was that the exoskeleton, providing the users with different amounts of assistive forces and requiring the use of walking aids, would induce changes in the amplitude of the muscle activations. More specifically, we hypothesized that the increase of the assistance would induce a decrease of the amplitude of the muscle activations without changing their timing. We will also expect that in individuals with residual walking ability, the adaptive paradigms will determine higher voluntary muscle activations than the maximum fixed assistance, which does not account for the individual ability and does not obey the assistance-as-needed protocol [23]. Our second hypothesis was that the mechanical structure of the exoskeleton would promote changes in the lower-limb muscle activation patterns that have been observed during normal overground walking, as suggested also by [20; 21]. With the long-term goal of extending this study to people suffering from neurological diseases or injuries, here we focused on healthy subjects that do not have alterations of their muscle patterns, reducing the possibility of variable and highly subjective responses to each of the investigated aspects.