4.) Testing reveals that Muscle Fiber 1 has the myosin heavy chain I (MHC-I) isoform, Muscle Fiber 2 has the myosin heavy chain IIa (MHC-IIa) isoform and Muscle Fiber 3 has the myosin heavy chain IIx (MHC II-x) isoform. Answer the following about these muscle fibers: a.) How would maximal velocity of shortening of Fiber 3 compare to that of Fiber 1? * What specific characteristic(s) within the fiber itself would be responsible for this difference? * How would these characteristics.