Some footballers love pre-season, some footballers hate pre-season.

Numerous fitness tests lay in store for every player to prove that they’re ready for the challenging season ahead.

It can be a daunting prospect - especially in the heat and after several weeks of luxury.

But some players just thrive when it comes to pre-season and that much was seen during a tough Liverpool training session.

Jurgen Klopp had his side perform a lactic acid fitness test.

The lactic acid test

According to an official definition: “It’s a test that measures the amount of lactic acid in your blood. This acid is made in muscle cells and red blood cells. It forms when your body turns food into energy.”

Liverpool players were instructed to jog around the pitch and after completing a lap, had a blood sample taken.

If the level of lactic acid in their blood exceeded a certain amount, they were out of the drill.

The likes of Roberto Firmino, Lucas Leiva, Joel Matic, Dominic Solanke, James Milner and Jordan Henderson all took part in the exercise.

While it’s unclear quite how many laps they performed, there were two men standing - Solanke and Milner. However, it appears as though the experienced Milner just pipped Liverpool’s new signing at the end.

Watch: Liverpool take part in lactic acid test

Take a look:

At the age of 31, Milner is still proving that he’s the ultimate professional and has probably been working hard throughout the summer to maintain his fitness levels. It certainly helps that he’s never had an alcoholic drink in his life.

Whether Milner will be called upon at left-back once again this season remains to be seen. Milner was almost an ever-present in the full-back position, being preferred to Alberto Moreno.

But Liverpool have been linked with Hull’s Andrew Robertson and the Reds are heavily expected to sign a left-sided defender this summer.

What that means for Milner is unknown but one thing is for sure, he’s still the model professional.