Trunk motion influences mechanical power estimates during wheelchair propulsion

Area of Science:

• Biomechanics
• Sports Science
• Rehabilitation Engineering

Background:

• Accurate measurement of mechanical power is crucial for wheelchair sports performance and training.
• Inertial Measurement Units (IMUs) can estimate power, but rely on accurate rolling resistance data.
• Trunk motion alters wheelchair mass distribution, potentially invalidating standard rolling resistance measurements like drag tests.

Purpose of the Study:

• To investigate the impact of trunk motion on mechanical power estimates during hand-rim wheelchair propulsion.
• To compare power loss calculated using instantaneous rolling resistance versus drag test-derived rolling resistance.
• To quantify the underestimation of mechanical power when trunk motion effects are ignored.

Main Methods:

• Wheelchair propulsion experiments were conducted with varying degrees of trunk motion (none, moderate, full).
• Mechanical power loss was calculated using two methods: instantaneous rolling resistance and drag test-based rolling resistance.
• Statistical analysis, including mean difference (MD) and correlation (r), was used to compare the methods.

Main Results:

• When no trunk motion occurred, power loss estimates were similar (0.6 ± 1.6% MD).
• With increased trunk motion, drag test-based power loss was underestimated by up to -3.3 ± 2.3% MD (r = 0.85).
• Neglecting trunk motion led to 1-6% underestimation of mechanical power.

Conclusions:

• Trunk motion significantly influences rolling resistance in wheelchair propulsion.
• Standard drag tests underestimate mechanical power when active trunk motion is present.
• Correction for trunk motion effects is recommended for accurate mechanical power estimation in wheelchair sports.