Broxterman and colleagues utilized lumbar intrathecal fentanyl and 31P-MRS to elucidate the influence of the lower limb group III/IV muscle afferents on intramuscular metabolic alterations and skeletal muscle bioenergetics during high-intensity exercise. Attenuation of group III/IV muscle afferent feedback resulted in greater changes in Pi, H2PO4ˉ, and ATP as well as faster rates of perturbation in PCr, Pi, H2PO4ˉ, pH, and ATP. Importantly, these faster rates of perturbation were the result of a greater ATP cost of contraction arising from the attenuation of afferent feedback. These findings support a critical role of group III/IV muscle afferents in constraining the magnitude of intramuscular metabolic perturbation during exercise, but, additionally, suggest a critical role of these muscle afferents in maintaining efficient skeletal muscle contractile function.
Finally, it is well known that chemotherapy agents can be very effective for treating cancer; however, many cancer survivors suffer from side effects of these drugs. To that end, Dickinson and coworkers investigated whether exercise can protect skeletal muscle from the harmful side effects of the anthracycline chemotherapy agent, doxorubicin, in rats. Their results demonstrate that aerobic exercise initiated prior to and continued during biweekly doxorubicin administration preserved important cellular mechanisms known to regulate muscle mass and also ultimately protected against reductions in skeletal muscle fiber size. Importantly, this pre-clinical study closely mimicked the dosing strategy used in the clinical treatment of breast cancer. The take-home message is that early incorporation of exercise in the progression of cancer treatment may provide an important strategy to protect skeletal muscle health, which could better preserve physical function following cancer treatment.
L. Bruce Gladden
School of Kinesiology