Comparing Physiological Responses to Single and Double Leg Submaximal Cycling in Normoxia and Hypoxia

Abstract

INTRODUCTION:It has been well established that exercise intensity as well as exercise performance declines at altitude. However, it has yet to be determined how femoral blood flow and muscle oxygenation kinetics (total tissue saturation, oxy- and deoxygenated hemoglobin, as well as total hemoglobin) are influenced by altitude during submaximal and maximal performances. Furthermore, it has yet to be determined if the utilization of small muscle mass exercise, which allows for greater blood flow to the active muscle, will allow an individual to generate the same muscle oxygenation kinetics in hypoxic conditions that is achieved during larger muscle mass activities in normoxia. PURPOSE: Thus, the purpose of this study was to determine if tissue oxygenation was compromised at altitude during submaximal bouts of exercise and whether reducing the active muscle mass exercise could be used to offset any observed decrement due to increases in blood flow. METHODS: 10 individuals performed double leg cycling for four minutes at 50%, 60%, 70% and 80% of their maximal oxygen consumption, rested for 15 minutes and then performed single leg cycling utilizing the same protocol but at half the double leg work rate in both normoxic and hypoxic conditions (oxygen concentration of 15% which simulated an altitude of 2,740 meters). RESULTS: The amount of blood flow during the single leg trial in hypoxia was significantly higher compared to blood flow during double leg cycling in hypoxia (p = 0.02). There was no significant difference between the single leg trial in hypoxia and the double leg trial in normoxia (p = 0.36) nor between the two double leg trials in normoxia and hypoxia (p = 0.87). No difference was found in the amount of oxygenated hemoglobin when comparing the single leg trial in hypoxia to the double leg trials in normoxia (p = 0.36) and hypoxia (p = 0.13). CONCLUSIONS: The results suggest that elevated hemoglobin saturation and femoral blood flow during the single leg condition in hypoxia are similar to that observed during double leg cycling in normoxia and may prove to be a viable training modality that would offset the main disadvantage of living at altitude by enabling an individual to exercise at the same level of intensity achieved at normoxia.