Segment interactions within the swing leg during unloaded and loaded running

Area of Science:

• Biomechanics
• Human Movement Science
• Sports Engineering

Background:

• Understanding lower extremity mechanics is crucial for optimizing running performance and preventing injuries.
• The swing phase of running involves complex interactions between joint kinetics and segment energetics.
• The role of external loads in modulating these interactions requires further investigation.

Purpose of the Study:

• To investigate the impact of manipulated lower extremity inertia on joint kinetics and segment energetics during the running swing phase.
• To differentiate the contributions of joint reaction forces versus net joint moments to lower extremity energetics.
• To assess how added lower extremity loads affect running movement patterns and energy transfer.

Main Methods:

• Fifteen male distance runners performed treadmill running at a constant velocity (3.35 m s-1).
• Five loading conditions were tested: no load, 0.25 kg, and 0.50 kg added to each thigh or each foot.
• Kinematic data were collected to analyze joint kinetics and segment energetics during the swing phase.

Main Results:

• Lower extremity energetics during the swing phase were dominated by mechanical energy transfers between segments via joint reaction forces.
• Joint reaction forces redistributed mechanical energy more significantly than net joint moments, which reflected muscular work.
• Added lower extremity loads caused minimal changes to the swing leg's movement pattern but increased joint reaction forces and net moments proximally.

Conclusions:

• Mechanical energy transfer through joint reaction forces is a primary driver of lower extremity energetics during the running swing phase.
• Increased lower extremity inertia primarily affects proximal joints, consistent with higher aerobic demands.
• Neuromuscular control strategies for leg motion during running are influenced by changes in lower extremity inertia.