Cancer Fatigue: Does Forearm Muscle Mass and Handgrip Correlate with Fatigue Severity? (714)

Abstract

1.Discuss the concept of “catastrophic” fatigue and “central governor” fatigue theory.2.Recognize that by comparing forearm muscle mass, hand grip, and fatigue that there are relationships between variables which are altered by fatigue. Background. A “catastrophe” fatigue theory has muscle exhaustion and ATP depletion as the main mechanism which would correlate with muscle mass and composition. It is also hypothesized that a brain “central governor” controls muscle activity and that the human body functions as a complex system during exercise until a central brake prevents loss of homeostasis. A “central governor” fatigue theory places the fatigue mechanism in the subconscious brain which ensures homeostasis and protects muscle from damage. The governor “set point” may be altered by illness. Bioelectrical impedance (BIA) estimates of muscle mass are validated against MRI measured muscle mass. The main electron conductor with BIA is muscle. Muscle mass is inversely related to impedance (Z) and directly related to the muscle area (L2). Research objectives. We hypothesized that the relationship between maximum handgrip strength, segmental forearm muscle mass (L2/Z) and fatigue is altered in cancer-related fatigue (CRF) if fatigue is central in origin. Methods. Twenty individuals, ten healthy controls, and ten with CRF were studied. Data collected was: BFI, handgrip x 4 (dominant arm), and forearm BIA impedance. Results. The median total BFI score was 18 for controls and 45 for CRF. In those with CRF relative to healthy controls, there was a poor correlation between BFI and forearm muscle mass, between handgrip strength and BFI, and handgrip strength and muscle mass (Figures1-3, red, healthy controls; blue, CRF). Conclusion. This pilot study demonstrated in those with CRF a poor correlation between handgrip strength, forearm muscle mass and fatigue severity which differed from healthy controls. This suggests that the “central governor” which controls muscle activation is altered in CRF and that fatigue is unlikely to be arising from reduced muscle mass (peripheral fatigue). Implications for research, policy, or practice. Fatigue severity in CRF is unrelated to muscle mass and handgrip strength. Interventions to increase muscle are unlikely to relieve fatigue.