Explain how a slight (but smooth) contraction differs from a vigorous contraction of the same muscle. Use the concepts of multiple motor unit summation.

Video transcript

Hi, everybody. Welcome back. Our next question says which of the following examples best illustrates the summit effect of multiple motor unit activations. Choice, A typing on a keyboard with precise finger movements. B walking at a leisurely pace on a flat surface, C lifting a heavy barbell during weight lifting or d performing delicate surgical procedures. So when we talk about the summit effect of multiple motor unit activations, that means simply that you can activate multiple motor units at once and they work together to produce a greater force. So a summit effect, the effect of each one individually all added together. So a little bit of force, a little bit of force, a little bit of force, activate multiple units, they can combine together to produce greater amount of force. So when we look at our different examples here, only one is a situation where you might require a greater amount of force. And that would be choice C lifting a heavy barbell, all the others. A typing on a keyboard. B walking at a leisurely pace on a flat surface and d performing delicate surgical procedures all involve activating motor units, but all involve small amounts of force needed. So choice C we have a large amount of force needed to lift, lift something heavy. So you'd want to activate multiple motor units that can work together to accomplish it. So choice C is correct because you need a greater amount of force. So try, see our correct answer here. See you in the next video.