Human Anatomy & Physiology (Human Body Systems)

Unit 1: Unit 1: Identity (Tissues, Bones, Muscles)HBS 1.2Human Body Systems: kinesiology & sensor data

Collect EMG/ROM sensor data

Use sensors to record a muscle's electrical signal (EMG) and read clean motion data.

Builds on (2 levels back)inferred · high confidence

Muscles contract on a signal: A muscle shortens when the nervous system tells it to; that command is electrical, which is what the sensor will pick up.
Reading a value off a graph or readout: Before collecting EMG, you need to read a number off a sensor display and tell a big reading from a small one.

Prerequisites are inferred: pending teacher review.

Re-learn the skill with worked practice and clear examples.

EMG = electromyography: a sensor reads the electrical signal of a contracting muscle. Good placement and a clean baseline make the data usable.

Step 1: Define EMG

EMG (electromyography) is the recording of a muscle's electrical signal. A relaxed muscle gives a small, flat signal; a contracting muscle gives a larger signal.

Step 2: Place the electrodes

Electrodes are sticky pads that sit on the skin over the muscle you want to measure. If they sit over the wrong muscle, the data is about the wrong thing.

Step 3: Take a baseline first

Record the reading while the muscle is relaxed. That baseline is your 'quiet' value, so you can tell how much the signal rose during a contraction.

Practice

A student rests their arm, then squeezes a grip as hard as they can. Compared with the relaxed baseline, the EMG reading during the hard squeeze should be:

Reviewed

A.Lower than baseline
B.About the same as baseline
C.Higher than baseline
D.Exactly zero

Show the worked solution ▾

Answer: C. Higher than baseline

Step 1: Recall what EMG reads: EMG reads the electrical signal of the muscle. More contraction means more electrical activity.
Step 2: Compare to the relaxed baseline: A hard squeeze is a stronger contraction than rest, so its electrical signal is larger than the relaxed baseline.

Why it's right: A stronger contraction produces a larger electrical signal, so the EMG reading during a hard squeeze is higher than the relaxed baseline.

Why the others miss:

A: A stronger contraction does not lower the signal.
B: A contraction is different from rest, so the reading changes.
D: A working muscle is not electrically silent, so it is not zero.

Aligned to HBS: interpreting EMG output · reading level ~grade 9

Where you'd see this

A lab partner watches the live EMG trace jump up each time their teammate flexes, confirming the electrodes are on the right muscle.

Careers that use this

Physical Therapy Aide: Uses EMG readouts to show a patient when a muscle is actually activating during a movement.

Video library

Watch: Collect EMG/ROM sensor data

How Do We Study Muscle "Activation"? Electromyography (EMG) Explained | Corporis

Corporis

Guided notes

Fill these in as you work through the lesson.

Big idea: An EMG sensor records the electrical signal a muscle makes when it contracts, turning an invisible body process into a number you can graph.

Key terms: write the meaning

EMG (electromyography) (what the sensor reads from a muscle):
Electrode (the sticky pad that touches the skin):
Sensor (the tool that turns a body event into data):
Baseline (the reading when the muscle is relaxed):

The rule

An EMG sensor measures the signal of a contracting muscle, so a stronger contraction usually shows a reading than a relaxed muscle.

Check yourself

Where do the electrodes have to sit for the sensor to pick up the right muscle?
What should the EMG reading look like while the muscle is relaxed versus squeezing?
Why is a clean baseline reading useful before you start collecting data?

Work one example

You place EMG electrodes on a forearm muscle. The student rests, then makes a tight fist. Describe what you expect the sensor reading to do at rest and during the fist, and name what the sensor is actually measuring.