Peripheral Alterations Affect the Loss in Force after a Treadmill Downhill Run

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• Downhill running (DR) is crucial for trail running performance but remains less studied than uphill running.
• Understanding the physiological and neuromuscular demands of DR is essential for optimizing training and performance in trail runners.

Purpose of the Study:

• To investigate the cardiorespiratory response during a 15-minute downhill running bout.
• To evaluate the neuromuscular consequences following 15 minutes of downhill running in trail runners.

Main Methods:

• Seventeen trail running athletes completed a 15-minute DR trial at a -25% slope, targeting ~60% of maximal oxygen consumption (V̇O₂max).
• Maximal voluntary contraction torque (MVCt) and muscle contractility were assessed before and after the DR trial.
• Oxygen consumption (V̇O₂) and heart rate (HR) were monitored during the DR bout.

Main Results:

• V̇O₂ and HR showed a significant time-dependent increase during DR, indicating sustained cardiorespiratory strain.
• Post-exercise MVCt decreased significantly (-22.2%), primarily attributed to peripheral alterations rather than central fatigue.
• Muscle contractility parameters, including torque from potentiated doublets and single-pulse stimulation, were significantly impaired post-DR, alongside a small reduction in the M-wave.

Conclusions:

• Fifteen minutes of downhill running induces significant neuromuscular fatigue and impairment in trail runners, predominantly affecting peripheral muscle function.
• The observed V̇O₂ and HR drift during low-intensity DR may be influenced by muscle fatigue and exercise-induced muscle damage.
• Findings highlight the substantial physiological cost of downhill running, emphasizing the need for specific training adaptations for trail running.