Clyde1820

That's going to make it hard, unless you are doing other activities (ie gym strengthening workouts) to get those legs into better shape for such strains.

Can take quite awhile to re-make one's muscles into hard-charging units, if having been out of it for awhile or stepping up to another level.

Back in the day, I was fairly fit and strong. But I began competing regionally in distance running, particularly hill courses. Took a couple of years of very tough workouts and lots of stretching to accomplish the transition, and even then I was still fighting occasional over-work of the muscles for the next year or so. During that era, I had a serious amateur cyclist friend who took me out on some long-ish rides ... at his performance level. Thought I was fit, and I was for running, but good lord did those rides hammer my muscles. Could do 60 miles and more, then. Just not at "serious" levels of effort. After a couple of such hard rides, my muscles were screaming for a couple of days. Had the nutrition, electrolytes, hydration and cardio aspects all covered. But it turned out those muscles that were so tuned for mid-distance performance running in the hills just couldn't cope with the strains that hard cycling demanded of them.

I'd just take it bit slower, dialing down the efforts a bit, work on your leg strength and flexibility in the "offending" (strained) muscles ... and wait for the efforts to pay off. Might be awhile, if your current starting point is showing it's not quite up to snuff (for that level of effort). Be patient, it'll come.