In experiment 2 Effect of increasing weights on muscle twitc

In experiment 2 (Effect of increasing weights on muscle twitch) the average amplitude of the finger twitches increased with increasing weights. How can you explain this based on your understanding of a muscle contractions?

Solution

The amplitude of the finger twitches should increase with heavier weight because more fibers are recruited, thus more EMG activity is generated.If the weight gets progressively heavier, it is expected that it takes longer to develop enough tension for muscle contraction to occur. So it should take longer to produce a contraction. As we konw that the development of tensionis directly is proportional to the weight attached to the muscle .

A muscle twitch is usually divided into three phases: 1) the latent period

2) the contraction period

3) the relaxation period

As the stimulus amplitude continues to increase, an increasing number of motor units will be recruited so that the strength of the contraction, or tension, increases as well. Once all motor units in a muscle have been recruited, an increase in the stimulus amplitude will not result in any increase in tension. The contraction of a whole muscle can produce strong, weak or intermediate contractions depending upon how many motor units are stimulated.