Can muscle coordination explain the advantage of using the standing position during intense cycling?

Abstract

Objectives: When compared to seated, the standing position allows the production of higher power outputs during intense cycling. We hypothesized that muscle coordination could explain this advantage. To test this hypothesis, we assessed muscle activity over a wide range of power outputs for both seated and standing cycling positions.

Design: Nine lower limb muscle activities from seventeen untrained volunteers were recorded during cycling sequences performed in the seated and the standing positions at power outputs ranging from ∼100 to 700W at 90±5 revolutions-per-minute (RPM).

Methods: Integrated electromyography activity (iEMG), temporal patterns of the EMGs, and muscle synergies were analyzed.

Results: Muscle activity was underlain by four muscle synergies in both positions. Muscle synergies were similar in the two positions (Pearson's r=0.929±0.125). The activation patterns of knee and ankle extensor muscles and their associated synergies had different timings in the two positions (differences of ∼2-10% of cycle). No major timing changes were observed with power output (<2% of cycle). Differences in iEMG between the two positions depended strongly on power output in all but the calf muscle (medial gastrocnemius).

Conclusions: The number and structure of the muscle synergies play a minor role in the advantage of using the standing position when cycling at high power-outputs. However, the standing position is favorable in terms of iEMG at power outputs ≳500-600W due to position-dependent modulations of muscle activation levels. These data are important for understanding the determinants of the seat-stand transition in cycling.

Keywords: Cycling; Locomotion; Muscle synergy; Performance.