The most important statement of the abstract is this:
"These findings suggest that intense muscle activity, which generates high concentrations of lactate, will disrupt excitation-contraction coupling. This may lead to decreases in Ca2+ transients promoting a decline in tension development and contribute to muscle fatigue."
Another thing: IF lactate was such a great fuel then coaches and their science teams would be injecting lacate into runners veins before the start of races.
It is not a fuel, unto itself. It must be converted to glucose first. 90% of that takes place in either the liver or the heart. Another 5% takes place in the kidneys. Only ~5% takes place in muscle tissue that is NOT active in running. And, even then, who cares? How much lactate is in the body has very little to do with how well a runner performs. Associated fatigue in the contractile mechanisms (myosin-active cross-bridging) takes place when lactate levels are high. See the article cited!
For the layman, high lactate = high muscular fatigue! It's that simple.
Must do something else more productive!