Neuromechanical linkage between the head and forearm during running

Area of Science:

• Human biomechanics
• Evolutionary biology
• Neuroscience

Background:

• Running involves complex movements affecting head and gaze stability.
• A potential neuromechanical linkage between the head and forearm could aid in stabilizing the head during locomotion.
• The biceps brachii and superior trapezius muscles are hypothesized to mediate this linkage.

Purpose of the Study:

• To investigate the existence of a neuromechanical link between the head and forearm during human running.
• To determine if this linkage is mediated by the biceps brachii and superior trapezius muscles.
• To understand the role of this linkage in head and gaze stabilization during running versus walking.

Main Methods:

• Thirteen participants performed walking and running on a treadmill.
• Motion capture recorded body segment kinematics.
• Electromyography measured muscle activation in the biceps brachii and superior trapezius.
• Perturbations were introduced by adding mass to the head and hand.

Main Results:

• A neuromechanical linkage between the head and forearm was confirmed during running, mediated by the biceps and superior trapezius.
• Muscle activations were temporally linked during the running stride cycle.
• Adding mass to the head or hand increased activation in both muscles during running.
• This linkage was not present during walking due to lower forces and stability demands.

Conclusions:

• The findings support a neuromechanical linkage that stabilizes the head and gaze during running.
• This linkage may have been a selective advantage in the evolution of long-distance running in early Homo.
• The synergistic muscle activation could have contributed to morphological changes seen in Homo erectus.