PRF1 and B-cell chronic lymphocytic leukemia: Muscle changes were accompanied by larger changes for monocyte phenotype and NK-cell characteristics, including absolute numbers, tumor cell cytotoxicity and expression of perforin and granzyme B. Together, these data suggest that HIIT-based exercise may be an important lifestyle intervention capable of improving physical and immunological functions critical to maintaining the health of older adults with treatment naïve CLL.