Pedal Motion Profile & Geometry in Ellipticals

Pedal Motion Profile

Pedal Motion Profile of an elliptical machine is the geometric description of how a pedal moves during one complete stroke cycle. It has three key parameters:

• Stride - Horizontal
• Lift - Vertical
• Pedal Tilt Range

This animated kinematic illustration simulates how a typical mid-range commercial elliptical machine produces a pedal motion profile:

For elliptical machines, different geometry designs present different pedal motion profiles.

Geometry in Elliptical Machines

Conventional ellipticals are based on a planar four-bar linkage mechanism.

The geometry design of the linkage determines the pedal trajectory, pedal tilt range, and overall machine dimensions.

Geometric Characteristics of Conventional Ellipticals

Large Flywheel Conventional ellipticals typically employ a large flywheel, which stores rotational kinetic energy essential for creating a smooth, low-impact resistance. The crank is typically integrated with, or directly attached to, the flywheel.

Long Machine Frame To achieve sufficient stride, the crank joint is usually positioned toward the edge of the large flywheel. Therefore, the coupler needs to be designed long enough to keep the pedal tilt range within an ergonomic range, usually less than 20°. A long coupler results in a long machine frame.

Horizontal Elliptical The large flywheel is usually set on the floor, and the coupler needs to remain mostly parallel to the floor. In such an arrangement, the pedal mounted on the coupler tends to follow a predominantly horizontal elliptical trajectory.

Pedal Motion Profile Variations

The geometric design of the linkage determines the Pedal Motion Profile (PMP). Conventional ellipticals usually fall into the following variations.

Long Coupler - Moderate Pedal Tilt

This Pedal Motion Profile from a long-coupler design is representative of a typical mid-range commercial elliptical machine.

Short Coupler - Steep Pedal Tilt

A short coupler leads to a shorter machine frame, but increases pedal tilt. This is one of the design models adopted in home-use ellipticals.

Short Crank - Reduced Stride-n-Lift

Short-crank design is another approach to reducing pedal tilt range while keeping the machine frame short.

This design leads to reduced motion range — smaller stride and lift. Usually, the flywheel is also downsized, giving this four-bar linkage elliptical a compact footprint.

Glide Track Design

Glide Track designs evolved from the conventional four-bar linkage by adding a hinged pedal bar to the coupler and a glide track to support the coupler. This architecture provides greater design freedom on pedal motion profile, allowing decent stride and lift while maintaining a moderate pedal tilt range, as well as a shorter machine frame.

In this design, the pedal is connected to the coupler through a pivot hinge, while the end of the coupler, instead of connecting to the rocker, rolls along a glide track.

This arrangement allows pedal stride, lift, and tilt to be configured more independently while remaining synchronized with the movement of the coupler.

With this design, ellipticals can be designed with shorter couplers and therefore shorter machine frames.

By supporting the other end of the coupler with a roller, Glide Track designs allow the flywheel to be positioned either at the front or the rear of the machine — front-drive or rear-drive.

Introducing LB007 Vertical Elliptical

The navymov LB007 is created by adding a two-stage transmission drivetrain to the four-bar linkage structure of a conventional elliptical.

High-Velocity Flywheel Unlike conventional ellipticals, where the four-bar linkage directly drives the flywheel, the LB007 has its four-bar linkage to drive the crank-wheel of a two-stage transmission drivetrain. The transmission then drives the flywheel at approximately 15 times the rotational speed of the crank-wheel.

Smooth Kinetic Transfer Due to its high-ratio speed transmission, LB007's scaled-down flywheel can store substantially more kinetic energy than the large flywheel of a typical conventional elliptical, allowing smoother kinetic transfer and improved movement continuity.

Compact Footprint LB007 is build with a small footprint due to its small flywheel and compact transmission drivetrain design, but yet achieves adequate motion range.

Its architecture allows greater geometry freedom in pedal motion design.

Through multiple rounds of biomechanical analysis and user feedback during the prototyping process, the LB007's pedal motion profile was refined as:

LB007 features a pedal motion profile of

Vertical Elliptical vs. Horizontal Elliptical

The terms vertical elliptical and horizontal elliptical describe the overall shape of the pedal trajectory.

In a conventional elliptical, the pedal typically follows a predominantly horizontal path. The horizontal stride is usually much greater than the vertical lift.

In a vertical elliptical, the opposite is true. Vertical lift becomes the dominant component of the pedal motion profile.

The two trajectories are illustrated below.

Conventional ellipticals evolved around a large floor-mounted flywheel. The linkage arrangement naturally favors a relatively horizontal pedal trajectory.

The LB007 employs a compact two-stage transmission drivetrain and a small flywheel. The reduced geometric constraints provide greater freedom in shaping the pedal trajectory.

From a kinematic perspective, the difference extends beyond geometry.

In a conventional elliptical, the four-bar linkage directly drives the flywheel. Pedal stroke rate and flywheel rotational speed are therefore equal.

In the LB007, the linkage drives a two-stage transmission drivetrain. The flywheel rotates approximately fifteen times faster than the crank-wheel.

The transmission enables substantial rotational kinetic energy storage without requiring a large flywheel. This allows the machine to maintain a compact structure while supporting the proprietary Vertical Elliptical 5×11™ pedal motion profile.

Summary

Elliptical geometry is primarily defined by the Pedal Motion Profile: horizontal stride, vertical lift, and pedal tilt range.

Conventional ellipticals use a four-bar linkage that directly drives a large flywheel. This architecture typically produces a predominantly horizontal pedal trajectory and often requires a long machine frame.

Design variations such as short couplers, short cranks, and Glide Track mechanisms are different ways to manage the tradeoff between machine size, stride, lift, and pedal tilt.

The LB007 follows a different design path. By adding a two-stage transmission drivetrain to the four-bar linkage architecture, it increases flywheel speed without relying on a large flywheel.

This compact drivetrain reduces geometric constraints and allows the LB007 to support the proprietary Vertical Elliptical 5×11™ Pedal Motion Profile: 5" horizontal stride, 11" vertical lift, and -1° to 18° pedal tilt range.