Red cell shape changes following trigger finger fatigue in subjects with chronic tiredness and healthy controls. SO Simpson; JC Murdoch; GP Herbison New Zealand Medical Journal 1993 Mar 24, 106(952):104-7. (UI: 93234043) Abstract: AIMS. To investigate the possibility of a correlation between the percentage of nondiscocytic erythrocytes and muscle fatiguability in subjects with the symptom of chronic tiredness. METHODS. Sixty nine volunteers suffering from persisting or intermittent tiredness and 72 healthy controls provided 3-drop samples of venous blood for red cell shape analysis before and after inducing fatigue in the trigger finger muscles by repeatedly pulling the trigger of an antique revolver. Elapsed time and the number of pulls were recorded. A work index was calculated from the number of trigger pulls divided by the time in seconds then multiplied by the number of trigger pulls. RESULTS. Subjects with tiredness had fewer discoid cells (males 62.5% vs 69.2%, p = 0.029; females 65.8% vs 71.8%, p = 0.002) than controls. They also had fewer trigger pulls (males 62.3 vs 84.0, p =0.003; females 29.5 vs 36.8, p = 0.042) and lower "work indices" (males 75.6 vs 104.7, p = 0.001; females 26.1 vs 39.6, p = 0.001) than controls at the first trigger pulling. After 5 minutes rest the number of trigger pulls for males was fewer than the controls (56.0 vs 64.2) but the difference was not significant, but the female values (24.3 vs 33.2) were significantly different (p = 0.008). Work indices for both sexes were significantly different from controls (males p = 0.020, females p = 0.001). CONCLUSIONS. The association of increased nondiscocytes and impaired muscle function could indicate a cause and effect relationship. This would be in agreement with the physiological concept of fatigue as a consequence of inadequate oxygen delivery.