Melissa is at the gym for a leg workout. They first start warming up by squatting with only the squat bar (45 lbs): this is an easy task for her. Then, she goes on to the main part of her workout: she squats 5 repetitions of her maximum load (175 lbs), stop to rest for 60 secs, then do so again, for a total of 5 x 5 repetitions.
A. In comparison to lifting 45 lbs, what had to happen in Melissa's muscle cells to allow her to lift 175 lbs?
B. Because the 175-lbs load is very heavy for Melissa, her coach has trained her to start her squat movement in a very specific position (see picture above). How does this position allow sarcomeres to generate more force?
C. Compare the 2 contractions (the one with 45 lbs and the one with 175 lbs): what is the expected difference in terms of latent period and muscle shortening velocity.
After her 5th block of 5 repetitions, Melissa's coach asks her to perform an extra "surprise" set, but, despite her best efforts, she can only do 2 repetitions. This is similar to what you observed in PEX-02-04, when you stimulated the muscle at 150 stimuli/sec and you observed the tension reaching a plateau before decreasing.
D. Explain what is likely happening to Melissa and list 2 cellular processes that may explain why this situation is occurring.
E. In this workout, which type of muscle fibers is Melissa mostly relying on? Explain your answer and list 2 characteristics specific to these muscle fiber type that allow Melissa's squatting workout.