Gait Adaptation to a Phase-Specific Nociceptive Electrical Stimulation Applied at the Ankle: A Model to Study Musculoskeletal-Like Pain

Abstract

Introduction: Lower limb pain, whether induced experimentally or as a result of a musculoskeletal injury, can impair motor control, leading to gait adaptations such as increased muscle stiffness or modified load distribution around joints. These adaptations may initially reduce pain but can also lead to longer-term maladaptive plasticity and to the development of chronic pain. In humans, many current experimental musculoskeletal-like pain models are invasive, and most don’t accurately reproduce the movement-related characteristics of musculoskeletal pain. The main objective of this study was to measure pain adaptation strategies during gait of a musculoskeletal-like experimental pain protocol induced by phase-specific, non-invasive electrical stimulation.Methods: Sixteen healthy participants walked on a treadmill at 4 km/h for three consecutive periods (BASELINE, PAIN, and POST-PAIN). Painful electrical stimulations were delivered at heel strike for the duration of heel contact (HC) using electrodes placed around the right lateral malleolus to mimic ankle sprains. Gait adaptations were quantified bilaterally using instrumented pressure-sensitive insoles. One-way ANOVAs and group time course analyses were performed to characterize the impact of electrical stimulation on heel and forefoot contact pressure and contact duration.Results: During the first few painful strides, peak HC pressure decreased on the painful side (8.6 ± 1.0%, p < 0.0001) and increased on the non-stimulated side (11.9 ± 0.9%, p < 0.0001) while HC duration was significantly reduced bilaterally (painful: 12.1 ± 0.9%, p < 0.0001; non-stimulated: 4.8 ± 0.8%, p < 0.0001). No clinically meaningful modifications were observed for the forefoot. One minute after the onset of painful stimulation, perceived pain levels stabilized and peak HC pressure remained significantly decreased on the painful side, while the other gait adaptations returned to pre-stimulation values.Discussion: These results demonstrate that a non-invasive, phase-specific pain can produce a stable painful gait pattern. Therefore, this protocol will be useful to study musculoskeletal pain locomotor adaptation strategies under controlled conditions.

Effect of movement‐evoked and tonic experimental pain on muscle force production

“…Painful electrical stimulation has traditionally been used to induce transient pain 17,18 . More recently, this technique has been used to investigate whether motor adaptations are a purposeful strategy to reduce the noxious stimulation 19–21 . For instance, by modulating in real time the amplitude of the stimulation based on the load applied to the right leg on the ground, we showed that participants were able to decrease their perceived pain intensity by redistributing the amount of weight between legs 21 .…”

“…17,18 More recently, this technique has been used to investigate whether motor adaptations are a purposeful strategy to reduce the noxious stimulation. [19][20][21] For instance, by modulating in real time the amplitude of the stimulation based on the load applied to the right leg on the ground, we showed that participants were able to decrease their perceived pain intensity by redistributing the amount of weight between legs. 21 Together with the fact that painful electrical stimulation delivered as low-frequency sinusoidal waveforms results in minimal habituation over time, 21 this experimental pain model offers a unique opportunity to directly compare motor adaptation to tonic and movement-evoked pain.…”

Effect of acute ankle experimental pain on lower limb motor control assessed by the modified star excursion balance test

“…For both groups, the intensity remained constant throughout the experiment. For more information regarding this experimental MSK-like pain protocol, see Bertrand-Charette et al ( 27 ).…”

Moving in pain - A preliminary study evaluating the immediate effects of experimental knee pain on locomotor biomechanics

“…Experimental pain intensity can be readily modulated based on the amplitude of electrical current [19][20][21][22], allowing for rapid changes in pain perceptions. Therein, pain can be induced based on movement mechanics in real time, such as plantar foot pressure during gait [23], ground reaction forces during standing balance [24], or wrist kinematics [20]. A limitation of this method is habituation with repeated or constant stimulation [25], but it appears this can be mitigated in the short term by using low frequency sinusoids [21,24,26].…”