After the euphoria of hitting a 5k first – did I mention I’d got a personal best? – I thought my running mojo had returned.

There’s nothing like achieving a goal you never knew you had until you smash it, like I did at Workington’s Festival of Running.

My mind is telling me that I’ve got to get into gear and start training properly for the Great North Run.

This need was galvanised by a cheery email from the organisers asking how training was going as there’s only 10 weeks left.

Ten weeks? How on earth did that happen?

I set off with the best of intentions on Monday. I was going to run the three times a week I set aside for myself.

I was going to get myself motivated.

By the time Monday evening came round, I felt as though someone was stabbing my right leg with millions of tiny pins.

I had hurt my back a couple of weeks ago and although that had settled down, the ghost of sciatica has remained with me.

I’m not calling it sciatica. Hate it when people say ‘I’ve got sciatica’ and then you see them down the disco having a boogie on the dancefloor.

That’s not sciatica, love. When I had that, I could not move for about four weeks as every minor jerk left me shuddering in agony.

This time round that nerve is just kind of reminding me it’s there and warning me not to get too full of myself as it could strike at any second.

I’d managed to fend it off round the official 5k, but obviously it’s a vindictive nerve and it was payback time.

I emailed Sam to tell her I wouldn’t make it and would try for Thursday instead.

She suggested I try her core class, which is on a Tuesday.

I’m not very good at diplomacy. Instead of saying something like, “I’m sorry Sam, I have a previous appointment”, I blurted out that I was scared of it.

Also, it was at something like 5.30pm. Now seeing as I struggle to get to 7.30pm classes with work, there was no way I was getting to an earlier one.

Especially one that looks like mental torture for a fat lass.

I’ve only ever seen it on the BodyFit page when they’ve taken pictures at classes.

I know it can’t be so (we have official BodyFit kit and there’s none of these for sale), but in my head I superimpose the participants wearing proper leotards a la the Green Goddess circa 1987, although I’m never sure if there are leg warmers.

They all look super lithe and athletic. It’s not a place I really want to waddle in to as a newbie.

Core also involves a massive beach ball affair, which you use as part of the exercises.

Again, I’ve seen photos of the exercises.

It seems to involve balance. A lot of balance on the ball.

I told the husband about Sam’s invite.

He snorted into his cup of tea.

“That’s the one with the massive beach ball, isn’t it? Sam has met you?” he asked. “She does know you can fall off a pavement with no help from anybody, let alone from the top of a massive yoga ball thing?”

I don’t do leotards either.