Related Experiment Video
Updated: Oct 4, 2025
07:30
Muscle Imbalances: Testing and Training Functional Eccentric Hamstring Strength in Athletic Populations
Published on: May 1, 2018
15.5K
Evaluation of the relationship between joint torque and angular velocity using a modified leg extension machine
Yoshikiyo Kanada1, Hiroaki Sakurai1, Yoshito Sugiura1,2
1Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Aichi, Japan.
Fujita Medical Journal
|February 3, 2022
Summary
Modifying a leg extension machine to prevent weight freefall did not significantly alter knee extensor torque or angular velocity during one repetition maximum (1RM) testing. This suggests the modification may offer a safer method for assessing knee extensor strength.
Area of Science:
- Biomechanics
- Exercise Physiology
Background:
- Leg extension machines can induce eccentric knee extensor contractions due to weight freefall after maximal extension.
- This can lead to cumulative fatigue, potentially compromising the reliability of torque measurements.
Purpose of the Study:
- To investigate the relationship between joint torque and angular velocity in one repetition maximum (1RM) knee extension.
- To assess the impact of a modified leg extension machine (preventing counter-rotation) on these parameters.
Main Methods:
- Twenty-one healthy men performed knee extensions on a modified leg extension machine.
- Two-dimensional analysis calculated joint torque and angular velocity.
- A regression equation estimated maximal isometric torque.
Main Results:
- Joint torque and angular velocity showed a non-significant trend of increase post-modification.
- Estimated maximal isometric torque remained unchanged after the machine modification.
Conclusions:
- Machine modification did not significantly alter key performance metrics.
- The modified leg extension machine may provide a safer approach for 1RM knee extensor torque assessment.
Related Concept Videos
01:15Torque Free Motion
582
The torque-free motion refers to the movement of a rigid body in space when no external torques are acting upon it. This type of motion can be observed in environments where there are no external forces or frictions, like in outer space. For example, a rotation of Mars in space is a torque-free motion. Mars is an axisymmetric object, meaning it has an axis of symmetry along which it rotates, designated as the z-axis. The rotating frame of reference is defined such that the center of mass of...
582
01:19Net Torque Calculations
9.8K
When a mechanic tries to remove a hex nut with a wrench, it is easier if the force is applied at the farthest end of the wrench handle. The lever arm is the distance from the pivot point (the hex nut in this case) to the person’s hand. If this distance is large, the torque is higher. Only the component of the force perpendicular to the lever arm contributes to the torque. Therefore, pushing the wrench perpendicular to the lever arm is more advantageous. If multiple people apply force to...
9.8K
01:14Mechanical Efficiency of Real Machines
906
The mechanical efficiency of a machine is a fundamental concept that describes how effectively a machine can convert input work into output work. According to this concept, the efficiency of a machine is equal to the ratio of the output work to the input work. An ideal machine, meaning a machine that has no energy losses, has an efficiency of one. This implies that the input work and the output work are equal.
However, in reality, no machine can be truly ideal, and all of them experience some...
However, in reality, no machine can be truly ideal, and all of them experience some...
906
01:13Angle of Twist: Problem Solving
428
An electric motor applies a torque of 700 N·m to an aluminum shaft, triggering a stable rotation. Two pulleys, B and C, are subjected to torques of 300 N·m and 400 N·m, respectively. The modulus of rigidity is provided as 25 GPa. With the knowledge of the length and diameter of each segment, the twist angle between the two pulleys can be computed. First, a section cut is made between pulleys B and C, and the cut cross-section is analyzed using a free-body diagram. Given that the...
428
01:21Relation Between Moment of a Force and Angular Momentum
814
In the realm of spinning tops, the application of force at a distance from the center produces torque, a pivotal factor that alters the angular momentum of the top, thereby inducing its rotation. The concept of moment, akin to linear force in rotation, quantifies how a force acting upon an object initiates rotational motion. Angular momentum serves as the rotational counterpart to linear momentum, representing an object's inherent tendency to persist in its rotational state.
The temporal...
The temporal...
814
01:11Angular Velocity and Acceleration
9.9K
We previously discussed angular velocity for uniform circular motion, however not all motion is uniform. Envision an ice skater spinning with their arms outstretched; when they pull their arms inward, their angular velocity increases. Additionally, think about a computer's hard disk slowing to a halt as the angular velocity decreases. The faster the change in angular velocity, the greater the angular acceleration. The instantaneous angular acceleration is defined as the derivative of...
9.9K