Vernier Software and Technology
Vernier Software & Technology

Introduction to Electromyography

Figure from experiment 3 from Human Physiology Experiments


Voluntary muscle contraction is the result of communication between the brain and individual muscle fibers of the musculoskeletal system. A thought is transformed into electrical impulses which travel down interneurons and motor neurons (in the spinal cord and peripheral nerves) to the neuromuscular junctions that form a motor unit.

The individual muscle fibers within each motor unit contract with an “all or none” response when stimulated, meaning the muscle fiber contracts to its maximum potential or not at all. The strength of contraction of a whole muscle depends on how many individual fibers are activated, and can be correlated with electrical activity measured over the muscle with a technique called electromyography, or EMG.

Regular exercise is important for maintaining muscle strength and conditioning. The most common form of non-aerobic exercise is isotonic (weight training). In isotonic exercise, the muscle changes length against a constant force. In isometric exercise the length of the muscle remains the same as greater demand is placed on it. An example of this is holding a barbell (or suitcase) in one position for an extended period of time. Muscle fatigue occurs with both forms of exercise.

In this experiment, you will use the Hand Dynamometer to measure maximum grip strength and correlate this with electrical activity of the muscles involved as measured using the EKG Sensor. You will see if electrical activity changes as a muscle fatigues during continuous maximal effort. Finally, you will observe the results of a conscious effort to overcome fatigue in the muscles being tested.


  • Obtain graphical representation of the electrical activity of a muscle.
  • Correlate grip strength measurements with electrical activity data.
  • Correlate measurements of grip strength and electrical activity with muscle fatigue.
  • Observe the effect on grip strength of a conscious effort to overcome fatigue.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Human Physiology Experiments

See other experiments from the lab book.

1Body Temperature
2Limb Position and Grip Strength
3Introduction to Electromyography
4Simple Neuromuscular Reflexes
6Homeostasis and Autonomic Reflexes
7Effect of Exercise on Heart Rate
8Introduction to Electrocardiography
9Blood Flow and Skin Temperature
10Respiration and Ventilation
11Ventilation and Heart Rate
12Oxygen Extraction During Respiration
13Effect of Exercise on Oxygen Usage
14Heart Rate and Calories

Experiment 3 from Human Physiology Experiments Lab Book

<i>Human Physiology Experiments</i> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

Buy the Book

Dev Reference: VST0807

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