# Effect of PEMF on Muscle Oxygen during Cycling:
###### Abstract  
Pulsed electromagnetic fields (PEMFs) are used as non-invasive tools to enhance microcirculation and tissue oxygenation, with a modulatory influence on the microvasculature. This study aimed to measure the acute effect of PEMF on muscle oxygenation and its influence on pulmonary oxygen kinetics during exercise. Eighteen male cyclists performed, on different days, a constant-load exercise in both active (ON) and inactive (OFF) FEMF stimulations while deoxyhemoglobin and pulmonary oxygen kinetics, total oxygenation index, and blood lactate were collected. PEMF enhanced muscle oxygenation, with higher values of deoxyhemoglobin both at the primary component and at the steady-state level. Moreover, PEMF accelerated deoxyhemoglobin on-transition kinetic, with a shorter time delay, time constant, and mean response time than the OFF condition. Lactate concentration was higher during stimulation. No differences were found for total oxygenation index and pulmonary oxygen kinetics. Local application of a precise PEMF stimulation can increase the rate of the muscle O\({}_{2}\) extraction and utilization. These changes were not accompanied by faster oxygen kinetics, reduced oxygen slow component, or reduced blood lactate level. It seems that oxygen consumption is more influenced by exercise involving large muscle mass like cycling, whereas PEMF might only act at the local level.  
oxygen uptake kinetics; constant load; lactate; performance; deoxyhemoglobin +
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in response to the release and to the vasodilatory effect of nitric oxide [8]. In adult people, it has been found that PEMF could affect peripheral resistance and microcirculation, with a decrease in systolic blood pressure [9]. [PERSON] and [PERSON] [10] explored the consequence of a PEMF exposure (27.12 MHz, 600 pulses/s, 0.1 mT) on human skin microcirculation. A laser doppler probe was positioned on both forearms of healthy participants. It was shown that 40 min of stimulation augmented significantly blood perfusion in the exposed arm (by 29%) and unchanged perfusion in the control arm. Additional use of the pulse sequence used by [PERSON] and [PERSON] was efficacious in rising blood perfusion in per-ulcer skin microcirculation, enhancing capillary blood velocity and diameter in diabetic patients [11; 12].  
To the best of our knowledge, no investigation has evaluated the effects of PEMF on the human muscle tissue level during exercise, and, more precisely, on factors of endurance capacity that are related to performance--such as faster oxygen kinetics, reduced oxygen slow component, or reduced blood lactate level--at high submaximal workload. The rate at which pulmonary O2 uptake increases after the onset of exercise is a determinant of sport performance and an indicator of well-done state of oxidative energetic system activity [13]. Specifically, a faster increase in VO2 after the onset of exercise indicates a greater muscle O2 utilization is a feature common in elite athletes and trained subjects due to the lower mismatch between muscle oxygen delivery and utilization [14].  
Considering the influence of PEMF on microcirculation, vascularization, and tissue oxygenation, seen above, and given that endurance exercise changes the microvascular oxygenation profile following the onset of contractions [15], we sought to evaluate the effect of PEMF stimulation on muscle tissue oxygenation and its influence on pulmonary oxygen kinetics during heavy aerobic exercise in cyclists. We collected both tissue oxygenation index (TOI) and deoxyhemoglobin (HHb) values, which are influenced by skin blood flow in the former, and reflect the rate of the muscle O2 extraction and utilization in the latter [16]. We hypothesized that PEMF stimulation should result in higher O2 muscle supply during exercise through increased O2 release and uptake. Moreover, we expected faster HHb kinetics due to the increased muscle O2 availability leading to faster adaption of workload and a decrease in O2 deficit related to the metabolic demand.