Corticospinal excitability changes following downhill and uphill walking

Area of Science:

• Neuromuscular Physiology
• Exercise Science
• Motor Control

Background:

• Locomotor exercise can alter corticospinal excitability and cortical inhibition in knee extensors.
• The specific mode of muscle contraction during locomotion may differentially affect neural responses.

Purpose of the Study:

• To investigate if treadmill walking mode (uphill vs. downhill) modulates corticospinal and intracortical excitability in knee extensors.
• To determine the specific effects of eccentric contractions during downhill walking on neuromuscular function.

Main Methods:

• Eleven subjects underwent 45-minute treadmill walking sessions in uphill (+15%) and downhill (-15%) conditions at matched speeds.
• Measurements included maximal voluntary isometric torque (MVIC), voluntary activation level (VAL), doublet twitch torque, M-wave, motor-evoked potential (MEP), cortical silent period (CSP), and short-interval cortical inhibition (SICI) in knee extensor muscles.
• Assessments were conducted pre- and post-exercise.

Main Results:

• Both uphill and downhill walking similarly reduced MVIC, VAL, and VL M-wave area.
• Doublet twitch torque decreased only after downhill walking.
• VL muscle MEP area increased significantly after downhill walking, but not after uphill walking; RF muscle MEP remained stable.
• CSP and SICI showed no significant changes in either condition for both muscles.

Conclusions:

• Downhill walking, characterized by eccentric muscle contractions, specifically enhances corticospinal excitability in the vastus lateralis muscle.
• The findings suggest that the eccentric muscle contraction mode during locomotor exercise can selectively modulate corticospinal excitability.
• Uphill walking did not elicit the same increase in corticospinal excitability.