Biomechanical factors affecting energy cost during running utilising different slopes

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Running economy is crucial for middle- and long-distance runners.
• Understanding the impact of varying slopes on running mechanics and energy expenditure is essential for performance optimization.

Purpose of the Study:

• To investigate how electromyography (EMG) and kinematics of the supporting leg influence energy cost during running on incline, level, and decline slopes.
• To identify specific muscle activation patterns and joint movements associated with changes in running energy cost across different gradients.

Main Methods:

• Twelve male Japanese middle- and long-distance runners participated.
• Subjects ran at 13.5 km/h on a treadmill under incline, level, and decline conditions.
• Sagittal plane kinematics, lower limb muscle EMG, and respiratory gases were recorded.

Main Results:

• Energy cost was significantly lower on decline slopes and highest on incline slopes.
• Integrated EMG (iEMG) of leg extensors, gastrocnemius, and soleus muscles increased with energy cost, particularly on inclines.
• Incline running involved greater knee and ankle extension (plantarflexion), potentially disrupting joint coordination and increasing muscular work.

Conclusions:

• Running economy is significantly affected by slope gradients, with incline running being the most energetically costly.
• Increased iEMG in leg extensor muscles and altered knee/ankle kinematics during incline running contribute to higher energy demands.
• Optimizing running technique to enhance inter-joint coordination and efficient muscle work may improve running economy across different terrains.