This study investigated the repeated-sprint ability (RSA) physiological responses to a standardized, high-intensity, intermittent running test (HIT), maximal oxygen uptake (VO(2) (max)) and oxygen uptake (VO(2)) kinetics in male soccer players (professional (N = 12) and amateur (N = 11)) of different playing standards. The relationships between each of these factors and RSA performance were determined. Mean RSA time (RSA(mean)) and RSA decrement were related to the physiological responses to HIT (blood lactate concentration ([La(-)]), r = 0.66 and 0.77; blood bicarbonate concentration ([HCO(3)-]), r = -0.71 and -0.75; and blood hydrogen ion concentration ([H(+)]), r = 0.61 and 0.73; all p < 0.05), VO(2) (max) (r = -0.45 and -0.65, p < 0.05), and time constant (tau) in VO(2) kinetics (r = 0.62 and 0.62, p < 0.05). VO(2) (max) was not different between playing standards (58.5 +/- 4.0 vs. 56.3 +/- 4.5 mL.kg(-1).min(-1); p = 0.227); however, the professional players demonstrated better RSA(mean) (7.17 +/- 0.09 vs. 7.41 +/- 0.19 s; p = 0.001), lower [La-] (5.7 +/- 1.5 vs. 8.2 +/- 2.2 mmol.L(-1); p = 0.004), lower [H+] (46.5 +/- 5.3 vs. 52.2 +/- 3.4 mmol.L(-1); p = 0.007), and higher [HCO3-] (20.1 +/- 2.1 vs. 17.7 +/- 1.7 mmol.L(-1); p = 0.006) after the HIT, and a shorter in VO2 kinetics (27.2 +/- 3.5 vs. 32.3 +/- 6.0 s; p = 0.019). These results show that RSA performance, the physiological response to the HIT, and differentiate between professional- and amateur-standard soccer players. Our results also show that RSA performance is related to VO(2) max, tau, and selected physiological responses to a standardized, high-intensity, intermittent exercise.

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BackgroundMesangiogenic progenitor cells (MPCs) have shown the ability to differentiate in-vitro toward mesenchymal stromal cells (MSCs) as well as angiogenic potential. MPCs have so far been described in detail as progenitors of the mesodermal lineage and appear to be of great significance in tissue regeneration and in hemopoietic niche regulation. On the contrary, information regarding the MPC angiogenic process is still incomplete and requires further clarification. In particular, genuine MPC angiogenic potential should be confirmed in-vivo.MethodsIn the present article, markers and functions associated with angiogenic cells have been dissected. MPCs freshly isolated from human bone marrow have been induced to differentiate into exponentially growing MSCs (P2-MSCs). Cells have been characterized and angiogenesis-related gene expression was evaluated before and after mesengenic differentiation. Moreover, angiogenic potential has been tested by in-vitro and in-vivo functional assays.ResultsMPCs showed a distinctive gene expression profile, acetylated-low density lipoprotein uptake, and transendothelial migration capacity. However, mature endothelial markers and functions of endothelial cells, including the ability to form new capillaries, were absent, thus suggesting MPCs to be very immature endothelial progenitors. MPCs showed marked 3D spheroid sprouting activating the related molecular machinery, a clear in-vitro indication of early angiogenesis. Indeed, MPCs applied to chicken chorioallantoic membrane induced and participated in neovessel formation. All of these features were lost in mesengenic terminally differentiated P2-MSCs, showing definite separation of the two differentiation lineages.ConclusionOur results confirm the bona-fide angiogenic potential of MPCs and suggest that the high variability reported for MSC cultures, responsible for the controversies regarding MSC angiogenic potential, could be correlated to variable percentages of co-isolated MPCs in the different culture conditions so far used.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-017-0562-x) contains supplementary material, which is available to authorized users.