Locomotor activities as a way of inducing neuroplasticity: insights from conventional approaches and perspectives on eccentric exercises

Abstract

Conventional locomotor exercise, such as cycling or walking, induces motor learning-like neuroplastic changes (i.e., decreased cortical inhibition and/or increased facilitation, assessed in a muscle using transcranial magnetic stimulation). These effects seem to be a consequence of humoral processes notably resulting from hemodynamic solicitation. Unfortunately, pathological populations may not be capable of exercising at sufficient intensities to trigger these beneficial neuroplastic modulations and an alternative method is needed. As it can be inferred from noninvasive brain and peripheral stimulation studies, a high neural activity can directly result in neuroplastic changes. Similarly, eccentric exercise (i.e., active lengthening of the muscle), during which individuals develop the same force or power as conventional exercise at lower cardiorespiratory intensities, requires a high brain neural activity. As single-joint eccentric exercise was decreased cortical inhibition and increased cortical facilitation, locomotor eccentric exercise may be even more potent by pooling neural and, maybe, hemodynamic neuroplastic processes.Further studies are required to understand the influence of locomotor exercise characteristics (e.g., intensity, duration) on exercise-induced neuroplasticity.

Corticospinal Excitability Is Lower During Eccentric Than Concentric Cycling in Men

“…Particularly, eccentric cycling (i.e., pedaling backward resisting the torque of an engine) has been serving as an alternative to conventional cycling rehabilitation among cardiorespiratory-limited patients ( Hoppeler, 2016 ). It has also been speculated that eccentric locomotor exercises could be a substitute to their concentric counterpart for neurorehabilitation (e.g., following a stroke; Clos et al, 2021 ). The rationale for this conjecture is as follows: while conventional locomotor exercises may trigger hemodynamic-related neuroplastic mechanisms ( Knaepen et al, 2010 ), eccentric locomotor exercises, by the repeated intense activation of motor neural networks, may promote neuroplasticity as well.…”

Concentric versus eccentric cycling at equal power output or effort perception: Neuromuscular alterations and muscle pain

“…It could even be efficient to counteract neurodegeneration. 6 However, these benefits do not guarantee that patients are willing to engage in eccentric cycling exercise that is part of a rehabilitation program. Their adherence to exercise prescription is impaired by fatigue, defined as "a disabling symptom" that impedes physical and cognitive function.…”

Motor and Visual Plasticity interact in Adult Humans

“…In humans too, physical exercise has been shown to promote ocular dominance plasticity in both normal sighted 56 and amblyopic 57 subjects. One crucial difference between physical activity and motor plasticity (either induced by learning or in response to a stroke) is that during physical activity, the E/I balance changes at the level of the motor cortex are still open to debate 58,59 . While studies clearly show that motor learning leads to a decrease in GABAergic inhibition in the human motor cortex [24][25][26][27] , changes induced by physical activity are not in consensus: although some studies defend a decrease in GABA 60,61 and increased excitability in corticospinal pathway [62][63][64] , others conclude decreased excitability [65][66][67] or higher GABA levels 68 .…”