Effects of coupled upper limbs movements on postural stabilisation.

Area of Science:

• Human movement science
• Biomechanics
• Motor control

Background:

• Coupled cyclic limb movements often exhibit a preference for in-phase coordination (mirror-symmetrical patterns).
• In-phase movements are generally perceived as easier to perform than anti-phase movements.

Purpose of the Study:

• To investigate the relationship between movement ease and postural activity during upper limb tasks.
• To quantify postural muscle involvement during single arm, in-phase, and anti-phase movements at various frequencies.

Main Methods:

• Kinematic data captured using infrared cameras.
• Ground reaction forces measured via a force platform.
• Surface electromyography (SEMG) recorded from key postural muscles.

Main Results:

• In-phase tasks demonstrated significantly less center of pressure (COP) displacement and torque production compared to anti-phase and single arm tasks.
• Reduced involvement of postural muscles (adductor longus, gluteus medius, rectus femoris, biceps femoris) was observed during in-phase movements.
• These findings were consistent across both sagittal and frontal planes.

Conclusions:

• The reduced need for postural control during in-phase movements likely explains their inherent ease of execution.
• This study provides biomechanical evidence supporting the preference for in-phase coordination in coupled limb movements.