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Related Concept Videos

Exercise and Muscle Performance01:27

Exercise and Muscle Performance

Exercise induces a range of adaptations in muscle tissue, depending on the type and duration of activity. Such physical training can be broadly categorized into two types: endurance exercises and resistance exercises.
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Power01:08

Power

The concept of work involves force and displacement; meanwhile, the work-energy theorem relates the net work done on a body to the difference in its kinetic energy, calculated between two points on its trajectory. While none of these quantities or relations involves time explicitly, we know that the time available to accomplish work is often just as important as the amount of work itself. For example, sprinters in a race may have achieved the same velocity at the finish, therefore,...
Instantaneous Power01:22

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Instantaneous power is important in electrical circuits, mainly when dealing with sinusoidal input. Instantaneous power, denoted as p(t), results from the multiplication of the instantaneous voltage (v(t)) across an element and the instantaneous current (i(t)) flowing through it. This relationship adheres to the passive sign convention and represents a fundamental principle in electrical engineering.
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Average Power01:13

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In practical electrical applications, the concept of time-varying instantaneous power is not frequently utilized. Instead, focus shifts to the more practical quantity known as average power. Average power is determined by integrating the instantaneous power over a specified time period and subsequently dividing it by that duration.

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Determining and Controlling External Power Output During Regular Handrim Wheelchair Propulsion
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Correlations between internal and external power outputs during weightlifting exercise.

Kristof Kipp1, Chad Harris, Michelle B Sabick

  • 1Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin, USA. kristof.kipp@marquette.edu

Journal of Strength and Conditioning Research
|June 29, 2012
PubMed
Summary

Optimizing athletic performance requires understanding training loads. This study found specific methods for calculating external power output correlate best with internal joint power at 85% of one repetition maximum (1RM) for the clean exercise.

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Area of Science:

  • Biomechanics and Exercise Physiology
  • Sports Science and Performance Optimization

Background:

  • Maximizing mechanical power during training is crucial for enhancing dynamic athletic performance.
  • Understanding the relationship between external power output and internal joint power is key to optimizing training strategies.

Purpose of the Study:

  • To investigate the correlations between external mechanical power output and internal mechanical joint power output across various loads during the clean exercise.
  • To determine which methods of calculating external power best predict internal joint power.

Main Methods:

  • Ten subjects performed the clean exercise at 65%, 75%, and 85% of their one repetition maximum (1RM).
  • External mechanical power was calculated using four common methods.
  • Internal joint power (hip, knee, ankle) and the sum of joint powers were calculated using inverse dynamics.
  • Power outputs were normalized using ratio scaling (W/kg) and allometric scaling (W·kg).

Main Results:

  • The highest number of significant correlations between internal and external power outputs occurred at 85% of 1RM.
  • At 85% 1RM, hip and knee joint power correlated with external power calculated via the work-energy method.
  • The sum of all joint powers correlated with external power calculated via the impulse-momentum method at 75% and 85% 1RM.
  • Allometric scaling yielded more significant correlations than ratio scaling.

Conclusions:

  • The work-energy method is recommended for inferring internal joint powers from external power outputs when lifting at 85% 1RM.
  • The impulse-momentum method can be used to infer the sum of internal joint powers from external power outputs at loads between 75% and 85% 1RM.
  • These findings aid in selecting appropriate methods for assessing power output in strength and conditioning settings.