The "slow component" of O2 uptake (VO2) kinetics during constant-load heavy-intensity exercise is traditionally thought to derive from a progressive recruitment of muscle fibers. In this study, which represents a reanalysis of data taken from a previous study by our group (Grassi B, Hogan MC, Greenhaff PL, Hamann JJ, Kelley KM, Aschenbach WG, Constantin-Teodosiu D, Gladden LB. J Physiol 538: 195-207, 2002) we evaluated the presence of a slow component-like response in the isolated dog gastrocnemius in situ (n=6) during 4 min of contractions at approximately 60-70% of peak VO2. In this preparation all muscle fibers are maximally activated by electrical stimulation from the beginning of the contraction period, and no progressive recruitment of fibers is possible. Muscle VO2 was calculated as blood flow multiplied by arteriovenous O2 content difference. The muscle fatigued (force decreased by approximately 20-25%) during contractions. Kinetics of adjustment were evaluated for 1) VO2, uncorrected for force development; 2) VO2 normalized for peak force; 3) VO2 normalized for force-time integral. A slow component-like response, described in only one muscle out of six when uncorrected VO2 was considered, was observed in all muscles when VO2/peak force and VO2/force-time were considered. The amplitude of the slow component-like response, expressed as a fraction of the total response, was higher for VO2/peak force (0.18+/-0.06, means+/-SE) and for VO2/force-time (0.22+/-0.05) compared with uncorrected VO2 (0.04+/-0.04). A progressive recruitment of muscle fibers may not be necessary for the development of the slow component of VO2 kinetics, which may be caused by the metabolic factors that induce muscle fatigue and, as a consequence, reduce the efficiency of muscle contractions.

We present the Hylaty geophysical station, a high-sensitivity and low-noise facility for extremely low frequency (ELF, 0.03-300 Hz) electromagnetic field measurements, which enables a variety of geophysical and climatological research related to atmospheric, ionospheric, magnetospheric, and space weather physics. The first systematic observations of ELF electromagnetic fields at the Jagiellonian University were undertaken in 1994. At the beginning the measurements were carried out sporadically, during expeditions to sparsely populated areas of the Bieszczady Mountains in the southeast of Poland. In 2004, an automatic Hylaty ELF station was built there, in a very low electromagnetic noise environment, which enabled continuous recording of the magnetic field components of the ELF electromagnetic field in the frequency range below 60 Hz. In 2013, after 8 years of successful operation, the station was upgraded by extending its frequency range up to 300 Hz. In this paper we show the station's technical setup, and how it has changed over the years. We discuss the design of ELF equipment, including antennas, receivers, the time control circuit, and power supply, as well as antenna and receiver calibration. We also discuss the methodology we developed for observations of the Schumann resonance and wideband observations of ELF field pulses. We provide examples of various kinds of signals recorded at the station.

[1] Asymmetric resonance curves are observed in various resonance systems occurring in nature. The reason for such a shape of the resonance curves is an interaction of the standing waves field in the resonator with the field of traveling waves which transmit energy from sources to the resonator. This behavior can be observed in strongly damped electromagnetic resonators. The ELF wave propagation inside the Earth-ionosphere cavity is a good example of the simultaneous occurrence of resonance and transmission phenomena. In this paper we show that the transmission field component depends on the attenuation rate of the Earth-ionosphere cavity and the observer-source distance. Besides, the resonance curve asymmetry causes an evident diurnal variability of the resonance frequencies. The superposition of the two components at any point of the resonator makes the analysis of the Schumann resonance (SR) difficult. Here we suggest a field decomposition method that allows separating the resonance component from the transmission one. Owing to the decomposition, having a single measurement of the E or B field, it is possible, independently of the observer position, to study the physical properties of the resonator as well as to determine the localization and the intensity of sources. The field decomposition permits defining new resonator parameters such as reduced resonance frequencies and reduced quality factors, independent of the observer position inside the cavity. We believe that the application of the decomposition method in the analysis of the ELF observations yields a possibility of improving the accuracy of the determination of both the distances and intensities of the sources exciting the Earthionosphere resonator, as well as its own parameters.

In this study, we hypothesized that 5 weeks of cycling endurance training can decrease the magnitude of the non-proportional increase in oxygen uptake (˙ V O 2) to power output relationship (˙ V O 2 'excess') at exercise intensities exceeding the lactate threshold (LT). Ten untrained, physically active men performed a bout of incremental cycling exercise until exhaustion before and after training. The mitochondrial DNA copy number, myosin heavy chain composition and content of uncoupling protein 3 and sarcoplasmic reticulum Ca 2+-ATPases (SERCAs) were analysed in muscle biopsies taken from vastus lateralis before and after training. The training resulted in an enhancement of the power-generating capabilities at maximal oxygen uptake (˙ V O 2 max) by ∼7% (P = 0.002) despite there being no changes in ˙ V O 2 max (P = 0.49). This effect was due to a considerable reduction in the magnitude of the ˙ V O 2 'excess' (P < 0.05) above the LT. A decrease in plasma ammonia concentration was found during exercise after training (P < 0.05). A downregulation of SERCA2 in vastus lateralis (P = 0.006) was observed after training. No changes in myosin heavy chain composition, selected electron transport chain proteins, uncoupling protein 3 or the mitochondrial DNA copy number (P > 0.05) were found after training. We conclude that the training-induced increase in power-generating capabilities at ˙ V O 2 max was due to attenuation of the ˙ V O 2 'excess' above the LT. This adaptive response seems to be related to the improvement of muscle metabolic stability, as judged by a lowering of plasma ammonia concentration. The enhancement of muscle metabolic stability after training could be caused by a decrease in ATP usage at a given power output owing to downregulation of SERCA2 pumps. The oxygen cost of cycling above the lactate threshold (LT) can be decreased after a few weeks of endurance training, as expressed by the lowering of the magnitude of the slow component of oxygen uptake (˙ V O 2) kinetics (Casaburi et al. 1987; Womack et al. 1995; Carter et al. 2000). However, the mechanism responsible for this effect remains unclear. There is a growing body of evidence to suggest that the increase in the oxygen cost of work during heavy-intensity exercise is caused by fatigue of the active muscle fibres (Zoladz et al. 2008; Hepple et al. 2010; Cannon et al. 2011) and, in particular, by a disturbance in the concentrations of muscle metabolites, i.e. a decrease in muscle phosphocreatine and a rise in free ADP, free AMP, free inosine monophosphate, creatine, inorganic phosphate and H + , potent to decrease muscle mechanical efficiency (Woledge, 1998; Zoladz et al. 2006). It is well known that endurance training can enhance muscle metabolic stability, i.e. lead to reduced changes in the concentrations of the above-mentioned muscle metabolites for a given ATP turnover (approximately