Upper limb and trunk muscle activity patterns during seated and standing cycling.

Area of Science:

• Biomechanics
• Human Physiology
• Exercise Science

Background:

• Understanding the functional roles of upper limb and trunk muscles during cycling is essential for optimizing performance and injury prevention.
• Previous research has primarily focused on lower limb contributions, leaving a gap in knowledge regarding upper body muscle involvement, particularly under varying power outputs.

Purpose of the Study:

• To elucidate the functional roles of specific upper limb and trunk muscles during both standing and seated cycling.
• To investigate how muscle activity and coordination change with increasing power output during cycling.

Main Methods:

• Surface electromyography (EMG) was used to measure the activity of seven upper limb and trunk muscles.
• Non-negative matrix factorization (NMF) was employed to identify muscle synergies during cycling at power outputs ranging from ~100-700 W.
• Three-dimensional handle and pedal forces were simultaneously recorded.

Main Results:

• Three distinct muscle synergies were identified: torso stabilization, trunk acceleration compensation/generation, and upper body weight support.
• Muscle activity transitioned from tonic to more phasic patterns as power output increased.
• Synergies remained largely consistent between seated and standing positions, with one synergy showing a phase shift during the pedal cycle.
• Significant increases in the activity of specific synergies were observed above ~500 W, particularly during the downstroke phases.

Conclusions:

• Upper limb and trunk muscles play significant functional roles in cycling, especially when high power outputs are demanded.
• The identified muscle synergies provide insights into the coordinated muscle actions contributing to cycling stability and force production.
• These findings have implications for training programs and performance enhancement in cycling disciplines requiring substantial power output.