The Science of Human-Machine Collaboration in Electric-Assist Bicycles: A Quantitative Study of Ebike Riding Efficiency

Introduction

In 2023, the global electric-assist bicycle (Ebike) market surpassed US$40 billion and continues to grow rapidly. Yet behind this commercial success, a scientific question remains under debate: Does riding an Ebike truly count as real exercise? And how can the collaboration efficiency between the electric-assist system and human power be scientifically quantified?

For competitive athletes, E-MTB (electric-assist mountain bike) events have become an independent racing discipline; for the general public, the Ebike serves both as a commuting tool and a means to increase daily physical activity. This article analyzes the operating principles of Ebike systems and research findings from the scientific perspective of human-machine collaboration efficiency.

Energy Flow in Ebike Drive Systems

Human-Machine Power Distribution Models

The power output of modern mid-drive Ebike systems (such as Bosch, Shimano EP8, and Brose) is determined jointly by human power and the motor:

$$P_{total} = P_{human} + P_{motor}$$

Different brands typically configure different Assistance Ratios:

Precision of Torque Sensing

High-quality Ebike systems use Torque Sensors rather than lower-cost cadence sensors, allowing precise reading of the rider’s force application at any point in the pedal stroke and real-time adjustment of motor output for a more natural assist feel. Research shows that torque-sensing systems score 35–40% higher than cadence-sensing systems on human-machine collaboration smoothness ratings (subjective perception scales).

Scientific Quantification of Physiological Load

Exercise Intensity of Ebike Riding

Multiple studies have compared the physiological intensity differences between Ebikes and conventional bicycles on identical routes:

Scientific Support for “It Still Counts as Exercise”

Although Ebikes reduce the rider’s absolute physiological load, multiple studies show that riding still meets the definition of “Moderate Intensity Physical Activity” (3–6 MET):

• WHO recommends adults engage in at least 150 minutes of moderate-intensity aerobic activity per week
• Commuter Ebike riders average approximately 4.5–5.5 MET per ride, meeting the threshold for effective exercise
• Studies also show that Ebike users ride significantly more minutes per week than conventional bicycle users (because distance and terrain barriers are easier to overcome)

Ebike Competitive Science: E-MTB

Physiological Demands of E-MTB Racing

Electric-assist mountain bike racing (E-MTB) has been officially recognized as a competitive discipline by the UCI. Compared with traditional MTB racing, the physiological characteristics of E-MTB include:

• Average speed increases by 25–40%, raising the technical demands of the course accordingly
• Longer stage distances (assist enables riders to complete longer stages), requiring greater aerobic endurance
• Battery management becomes a tactical element: switching between high and low assist modes resembles energy management strategies in motorsport

Interaction Between Motor Efficiency and Pedaling Cadence

Research has found that the electrical-to-mechanical conversion efficiency of Ebike mid-drive motors is highly correlated with rider cadence:

• Optimal efficiency cadence: 70–90 rpm (varies slightly by brand)
• Excessively low cadence (< 60 rpm): high motor torque output but low efficiency, accelerating battery drain
• Excessively high cadence (> 100 rpm): the motor must process higher-frequency torque input, and efficiency also drops slightly

This means Ebike riders should consciously maintain a reasonable cadence—not only for physiological efficiency but also to extend battery range.

Battery Efficiency and Energy Management

Factors Affecting Actual Range

Practical Recommendations

1. Choose a torque-sensing motor system: It provides a more natural human-machine collaboration feel and better encourages the rider to maintain active pedaling effort
2. Maintain an appropriate assistance ratio: Avoid using the highest assist mode the entire ride; keep rider power within the aerobic zone (moderate intensity) to gain health benefits
3. Manage cadence: Maintain a cadence of 75–85 rpm to balance both physiological efficiency and battery efficiency
4. Battery thermal management: Battery efficiency drops significantly in low-temperature environments (< 10°C); warm the battery to room temperature before departure

Related Reading

• Health Benefits of Electric-Assist Bicycles (E-bikes): Applications for Seniors and Rehabilitation
• Taiwan Market Trends for Electric-Assist Bicycles (E-Bikes)
• Electric-Assist Bicycles (E-bikes): Who Are They Suitable For
• Quantifying Riding Efficiency (GE/PE): How to Become a More Economical Rider