How it works

THE PRINCIPLE

Flywheel exercise devices provide resistance through repeated acceleration-deceleration cycles of a revolving flywheel - similar to a toy Yo-Yo

FULL STORY  –  See also Biomechanics

By concentric muscle contraction, the flywheel is set into rotation by pulling a strap wound around the flywheel axle. When fully unwound, the strap rewinds by virtue of the stored kinetic/rotational energy, while being decelerated by eccentric muscle action. The inertial load, or resistance, is dependent on the mass and size (radius of gyration), and the angular acceleration of the flywheel.

The net effect is that the trainee will encounter a resistance that varies over the exercise repetition, corresponding to his own effort and muscular strength in each joint position.

This feature is comparable to that of so-called isokinetic dynamometers which use an electric motor to resist any muscular effort while maintaining a preset joint angular velocity.

By increasing the size or number of flywheels, the velocity decreases and the load becomes heavier. Force and power output during flywheel exercise may either be directly measured using strain gauge, or be calculated by the rotational acceleration of the flywheel.

Because the flywheel inertia is typically unaltered during the exercise session, flywheel exercise is sometimes referred to as isoinertial training. See Biomechanical aspects: mechanical difference between the resistance by a flywheel compared to weights.

SCIENCE

The first scientific evaluation showed flywheel seated legpress and athletic incline legpress both produced the load of two-times bodyweight - exceeding 1700 N (160 kg). In fact, muscle activation and force output demonstrated eccentric overload vs. concentric phase.

Consequently, numerous scientific studies show increased strength and prompt muscle growth (hypertrophy) similar or exceeding that from barbell or weight-stack training.

Flywheel training of elderly individuals are highly effective to improve upper and lower limb strength (20-40%), balance and gait speed.

Flywheel training is highly effective to combat muscle loss from long-term simulated spaceflight (3 months bedrest).

 FULL STORY  –  Scientific publications referenced at the end

Muscle activation: The first scientific evaluation of flywheel exercise compared flywheel seated leg press and the athletic incline leg press. Forces exceeding 1700 N (160 kg), or 2 times bodyweight, were produced in both exercise models. Also, the electromyographic muscle activity and force output during the eccentric/braking phase exceeded the concentric phase, thus demonstrating eccentric overload. Numerous experimental studies have later confirmed the potential for high resistive loads and eccentric overload when performing flywheel exercise. Similar to traditional resistance training or other eccentric overload models, flywheel exercises induce substantial delayed onset soreness to the activated muscles, and a protective effect for renewed soreness in later exercise sessions. Such findings are commonly interpreted as an early training response and a confirmation that a strength-training model is effective.

Muscle adaptation: Training responses to flywheel exercise include increased strength and prompt muscle growth (hypertrophy). As the eccentric load is crucial to develop both muscle size and strength in any type of resistance training, these adaptations could be expected. Several studies have sought to determine if eccentric overload during flywheel exercise may cause unique adaptations to exercise; see below Sports performance. Flywheel training of elderly individuals was highly effective to improve upper and lower limb strength (20-40%), balance and gait speed. For adaptation in bedridden individuals, see Use in spaceflight.