Simulated work loops predict maximal human cycling power.

Area of Science:

• Biomechanics
• Human Physiology
• Motor Control

Background:

• Locomotor activities in animals like fish, birds, and lizards are known to maximize muscle power.
• It remains unknown if humans maximize muscle power during voluntary activities due to limitations of non-invasive experimental techniques.

Purpose of the Study:

• To investigate whether voluntary maximal cycling in humans is characterized by maximized muscle power.
• To compare simulated maximal muscle power with experimentally measured joint and leg power.

Main Methods:

• Utilized simulated muscle work loops with experimentally measured joint angles and anatomically realistic muscle parameters.
• Employed a published muscle model to calculate power and force for 38 individual muscles.
• Optimized stimulation onset and offset for each muscle to maximize work and power across the shortening/lengthening cycle.

Main Results:

• Simulated maximal leg, hip, and knee power closely approximated experimental power values (ICC > 0.91).
• Ankle power approximation was less close (ICC = 0.74), suggesting a power transfer role.
• Simulations revealed biarticular muscles can generate greater power at individual joints than their net muscle power output.

Conclusions:

• Human motor control strategies appear to optimize muscle activation for maximizing power at the hip and knee during maximal cycling.
• The ankle joint functions primarily for power transfer rather than power maximization.
• The work-loop simulation technique offers a valuable tool for assessing clinical deficits in muscle power production.