Physical work capacity and metabolic stress in subjects with iron deficiency anemia

Abstract

Seventy-five female subjects with hemoglobin (Hb) levels ranging from 6.1 to 15.9 g/100 ml were identified in a preliminary screening program of tea estate workers in the Kandy area of Sri Lanka (Ceylon). Venous blood samples were obtained for Hb, serum iron, total iron-binding capacity, P₅₀ (partial pressure of oxygen when Hb is 50% saturated with oxygen), 2,3-diphosphoglycerate (2,3-DPG), and lactate determinations before performing an 18-min multistage treadmill test. Heart rate (HR) was continuously monitored throughout the exercise period and for 3 min during recovery. Blood samples taken after exercise were measured for lactate. For analysis purposes, seven groups were established with 1 g/100 ml Hb increments from 6 to 13 g/100 ml and one group of >13 g/100 ml. Performance values for the lowest Hb group compared to the highest Hb group as measured by total time on the treadmill (10.4 versus 18.0 min), percentage of subjects that reached the highest work load (0 versus 100%), HR/work load at 4.4 km/hr, 10% grade (176 versus 130 beats/min), and postexercise lactate (4.9 versus 2.7 µmoles/ml of blood) all showed significant differences. The lowest Hb group also showed significantly increased oxygen delivery adaptation through higher 2,3-DPG levels (14.9 versus 11.3 µmoles/ml of blood) and higher P₅₀ values (31.3 versus 27.8 mm Hg) when compared to the highest Hb group. Because physical working capacity is significantly reduced by iron deficiency anemia, with a concomitant reduction in productivity, a strong case for its correction and prevention can be made on a basis of economics, as well as of health.