UKC

Starting the TMB from Col de Voza most of my first day out was downhill, a lttle bit steep in places. After a couple of hours I noticed a sort of weakness in my thigh muscles - in what I think might be known as the Rectus Femoris.

It seemed to cease when I did eventually start going up hill and never gave me any trouble again.

Just wondering if it was, in fact, because I suddenly started the day going downhill and perhaps the muscles hadn't "warmed up".

In reply to mypyrex:

Rectus femoris is a 2 joint muscle; it extends the knee, and flexes the hip when it contracts. It's got the single joint muscles, the hip flexors, and knee extensors to aid it.
Your brain 'learns' patterns of movement- and like the conductor of an orchestra playing a familiar piece, will have all the players coming in at just the right time, with the right force. Something unfamiliar and there may not be the same ease of action.
If you did a lot of sustained downhill, you'd likely develop an aptitude for it.
Hauling up, and lowering- muscles contracting, muscles lengthening. The same, but different.

In reply to mypyrex:

Maybe it's because if you set off uphill, the rapid onset of "shagged out & gasping for air" limits the stress you can put on your muscles, whereas romping merrily off downhill allows you to subject them to a good kicking.