6 research outputs found
Quantum liquids resulting from quark systems with four-quark interaction
Quark ensembles influenced by strong stochastic vacuum gluon fields are investigated within the four-fermion interaction approximation. The comparative analysis of several quantum liquid models is performed and this analysis leads to the conclusion that the presence of a gas–liquid phase transition is their characteristic feature. The problem of the instability of small quark number droplets is discussed and it is argued that it is rooted in the chiral soliton formation. The existence of a mixed phase of the vacuum and baryon matter is proposed as a possible explanation of the latter stability
Are there differences in performance, metabolism, and quadriceps muscle activity in black African and Caucasian athletes during brief intermittent and intense exercise?
The purpose of the present study was to determine
whether there are any differences in power output (PO) and/or
quadriceps muscle (Quad) activity between black African and
Caucasian football players during a force-velocity (fv) exercise
test, which consisted of performing maximal 6-s sprints against
an increasing load. Each subject started the test with a load of 2
kg and then recovered for 5 min before repeating the same test
with a load increased by 2 kg. When the pedal frequency did not
exceed 130 rev·min–1, the load was increased by only 1 kg.
Each subject attained the load corresponding to his maximal
power if an additional increase in load (+1 kg) induced a power
decrease. Nine black Africans (mean age 24.2 ± 3.3 years) and
nine Caucasians (24.7 ± 4.2 years) (matched for stature and
aerobic fitness) participated in the fv exercise test. During the
test, PO, blood lactate, and the quadriceps electromyography
(EMG) root mean square (Quad RMS) were assessed. Higher
blood lactate was observed in Caucasians than in black Africans
for POs over the load range from 4 kg up to the maximal power.
However, PO and Quad RMS values were similar in Caucasians
and black Africans. They also had similar lean leg volume (LLV)
and consequently produced similar PO/LLV and Quad RMS/LLV
values. Overall, our results suggest that Caucasians and black
Africans matched for stature, max, and training background
have similar PO and Quad RMS values, but different blood lactate
concentrations during brief, intermittent, intense exercise
performed on a cycloergometer