Murray could hardly have offered his observers a more emphatic riposte, outclassing Giraldo with a tactical masterclass.
"I'm very happy. I was just trying to make sure I got myself in the best shape possible for the match," the British number one told BBC 5 live.
"I was really surprised with the way I served because that was one of the things that was giving me trouble the other day and I hardly hit any in practice yesterday.
Jonathan OverendBBC tennis correspondent
No drama, no controversy, no treatment, no Virginia. This was business as usual for Murray after all the drama of Thursday. A thoroughly professional performance, holding serve throughout and hitting through his forehand with impressive timing and verve. Crucially, he moved impressively in and out of the corners with no obvious discomfort. From being a couple of points away from a crushing retirement, he's now in the last 16 looking in fabulous nick.
"He [physio Andy Ireland] has helped a lot. We've done two or three treatments each day to try and make sure I get better, seen the doctor, taken all the right medication, anti-inflammatories. Those guys have made a huge, huge difference."
Murray looked calm and relaxed throughout, not once berating himself as so often has been the case.
From the opening minutes, when he chased down a drop shot to win game one, the back problem seemed under control.
Giraldo was flashing huge winners from out wide but Murray contained him and broke for 4-2 when the Colombian netted a backhand.
A love hold completed the 28-minute first set, in which Murray conceded only three points on serve, and he was similarly comfortable at the start of the second.
Giraldo netted to go down a break in game five and Murray consolidated the advantage with an incredible crosscourt forehand for 4-2.
His only moment of angst came when serving for the set, but Giraldo netted on break point and his opportunity was gone.
An 18-minute first game of the third set, including a 29-shot rally, went the way of Giraldo and suggested he was far from done.
But Murray continued to serve impeccably and after taking his third break point in game seven to lead 4-3, he served out on his second match point with a crosscourt backhand winner.
fought back from dropping the first set to overcome qualifier Haas 6-7 (3-7) 6-3 6-0- 6-0.
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