Activity 5 of the Skeletal Muscle Physiology virtual lab. Hold a tetanus until force falls, then rest the muscle and see how much it recovers. Force rises to…
Background
Fatigue is a fall in force, or a failure to contract, after prolonged or repeated activity, even though stimulation continues. The practicum explains it by the build-up of lactic acid, ADP and inorganic phosphate after intense activity; reduced Ca²⁺ release also contributes.
Rest lets the muscle recover: it restores ATP and creatine phosphate, clears Pi and H⁺ and reloads the sarcoplasmic reticulum with Ca²⁺. The longer the rest, the more force returns.
Steps
Set the voltage to 8.5 V and the rate to 120 stimuli/s. Click Multiple Stimulus.
Let the tetanus continue while force declines, then click Stop Stimulus. Record Data.
Wait about 10 seconds (sweep time), click Multiple Stimulus again, then stop and Record Data.
Start a new sweep and repeat with a 20 second rest. Compare how much force returns after each rest.
What you should find
Force rises to a tetanic plateau, then falls steadily during continued stimulation. After a rest the muscle produces more force again, and the longer the rest, the greater the recovery.
Check your understanding
During continuous stimulation at 120 stimuli/s, force steadily falls. This is:
Which rest period lets the muscle recover the most force before restimulation?
According to the practicum, fatigue after intense activity is caused by the accumulation of: