MYH14 and cancer: Participants may have had more difficulty performing the endurance test because of balance problems [51], less motivation, cardiorespiratory limitations [2], central fatigue impacting motor performance [8] or muscle adaptations (atrophy of I-fibers, increased myosin fixation time in I-fibers, decreased mitochondrial density, and a shift to faster and more powerful IIa/IIx fibers) that occur with cancer [5,52].