By the end of a good day, I have mild fatigue in my thighs. If they're more tired than that, that means that I've been skiing too low and not extending through the turn as I know to do, then relaxing and flexing the legs to release the old turn and start the new turn.
I read Adam Steer's stuff, and I've gott'a admit that most of it didn't resonate with me. I couldn't get part of his videos to come through, so that might be part. I disagree with pushing the outside foot forward. The feet often are too far forward relative to the center of mass and need to be pulled back.
I don't tell folks to get their hips forward. I tell them to get their feet back behind them. When it feels like their feet are behind them, they're actually well centered. I tell beginners to keep their "center" (center of mass) between their toes, or above the toe on the outside of the turn.
On a green run we have a spot on the side where there is a sudden drop and a smooth runout. I draw a line in the snow right at the drop off and tell them that when their toes cross that line they're to strongly pull both feet back behind them. I tell them this rule of thumb...if their ski tips are in the air they have no control. Pulling the feet behind them pulls the tips down to the snow for control. We stand on the flat, slide to the drop off, and pull the feet strongly back when the toes cross the drop. It works great. They need to pull both feet back strongly at every drop off and and in every turn transition when the skis are light on the snow. The steeper the run the stronger the pull back needs to be. A good guide for many folks--pull the feet so far back that they disappear from your vision in your goggles. Another rule of thumb...you want to your weight to be on the balls of your feet in the top 1/3 of the turn and move to centered over your arches by the bottom of the turn. Then, strongly pull back at the transition to the next turn to get back on the ski tips to make the skis turn you (in addition to the edging, etc). The two halves of the ski have different jobs. The front half of the ski, when your weight is on it, turns you and slows you. The back half of the ski, when you put your weight back there, takes you for a ride, straight and fast.
During the turn, pull the inside foot strongly back all the time on every turn while simultaneously pushing the inside hip forward. It sounds contradictory, but it works well. There is no virtue in tip lead, it's just an indicator that we're bending the inside leg to get that ski out of the way so we can develop some angles while turning. Pulling the inside foot back prevents the weight from getting behind the feet. Pushing the inside hip forward provides the essential counter, and doing it as early as possible in the turn is an advantage, especially on steeps. Aim your zipper at your outside boot immediately in the new turn.
(Ski into the counter?...what is the science behind that old statement? Angles across the ski tips, ankles, hips, shoulders should be matched?...again, where's the science?)