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The Effects of Knee Joint Angle and Contractor Intensity on Perceived Exertion
Danny M Pincivero1, Staci M Thomas2
11 Department of Kinesiology, University of Waterloo, ON, Canada.
Perceptual and Motor Skills
|September 9, 2018
Summary
Knee joint angle significantly impacts perceived exertion during isometric contractions. Higher perceived exertion was noted at 90° for both knee extensors and flexors, indicating muscle length influences effort perception.
Area of Science:
- Exercise Physiology
- Biomechanics
- Human Movement Science
Background:
- Perceived exertion is a key indicator of exercise intensity.
- Understanding how joint angles affect perceived exertion is crucial for training.
- Isometric contractions are fundamental movements used in various physical activities and rehabilitation.
Purpose of the Study:
- To investigate the influence of knee joint angle on perceived exertion during isometric knee extension and flexion.
- To determine the relationship between contraction intensity and perceived exertion across different knee joint angles.
- To explore potential differences in neuromuscular control and muscle physiology contributing to perceived exertion.
Main Methods:
- Fourteen healthy adults performed isometric maximal voluntary contractions (MVCs) at five knee angles (10°, 30°, 50°, 70°, 90°).
- Submaximal contractions (10%-90% MVC) were assessed using the modified Borg scale immediately after each contraction.
- Procedures were repeated for both knee extensor and flexor muscles, with sessions separated by one week.
Main Results:
- Perceived exertion was significantly higher at 90° compared to 70° and 10° for knee extensors (p < .05).
- Significant interactions showed higher perceived exertion at 30° vs. 50° (60%-70% MVC) and vice versa (70%-80% MVC) for extensors (p < .01).
- For knee flexors, perceived exertion was significantly greater at 90° than all other angles (p < .05), with notable interactions between 50° and 70° across specific intensity ranges (p < .05).
Conclusions:
- The 90° knee angle elicits higher perceived exertion in both knee extensors and flexors, suggesting a pronounced effect of muscle length on sensory feedback.
- Observed angle-intensity interactions indicate complex neuromuscular adjustments influencing perceived effort.
- Differences in perceived exertion between knee extensors and flexors at various angles highlight distinct peripheral and central mechanisms related to muscle group-specific biomechanics and muscle length-dependent properties.
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