Cardiorespiratory and oxygenation responses in iron-deficient anemic women during whole-body exercise under moderate hypoxia

Abstract

Purpose Integrated physiological responses during maximal whole-body exercise, such as cycling, under additive hypoxemia (anemia + hypoxia) are not adequately studied. Therefore, we investigated cardiovascular, muscular and cerebral oxygenation responses in chronic mildly iron-deficient and control women under normoxic and moderate hypoxic conditions during maximal whole-body exercise. Methods In a randomized and counterbalanced order, 16 females performed incremental exercise to exhaustion under normoxia (N; FIO 2 :20.94%) and hypoxia (H; FIO 2 :13.6%). The participants were divided into two groups matched for age and anthropometric characteristics, but intentionally varying in [Hb] ( p < 0.001) and V̇O 2max ( p < 0.01); iron-deficient (A; n = 8; [Hb]:11.3 ± 0.4 g/dl; V̇O 2max :37.3 ± 2.8 ml/kg/min) and healthy controls (C; n = 8; [Hb]:13.3 ± 0.4 g/dl; V̇O 2max :40.8 ± 1.9 ml/kg/min). Results During exercise in hypoxia compared to normoxia, the A exhibited greater decrement in V̇O 2max (5.0%; p = 0.02) and peak power output (5.4%; p = 0.004) than C. Maximal mean arterial pressure was reduced ( p < 0.05) due to lower total peripheral resistance ( p < 0.05) and unchanged maximal cardiac output ( p > 0.05). Enhanced O 2 utilization under H was observed only in C, based on ΔHHb ( p < 0.05). Cerebral oxygenation was reduced linearly with CaO 2 ( r = 0.95, p < 0.001). Conclusion Collectively, moderate hypoxia induced greater reduction of V̇O 2max , peak power output and cerebral oxygenation leading to exercise intolerance in A compared to C. These responses were accompanied by an inability of skeletal muscle to increase O 2 utilization at maximal effort in H and by a failure of the cardiovascular system to compensate and counteract convective and diffusion limitations during maximal whole-body exercise in anemic women.

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