Easy rides more leg fatigue?
I've notice something this year and it makes no sense to me. I've done more long rides at low zone 2 power. But I swear my legs legs get more sore and fatigued than when I do them at a high zone 2 power. I'm talking long-ish rides of 3-4 hours in length and relatively flat most of the time. So, a fairly constant intensity with few if any surges.
Obviously a higher intensity has to be more fatiguing overall, but is there a reason a lot of low intensity could cause more muscle soreness than the same ride done at higher intensity?
FYI, these are typically 50+ mile rides and I do this about once a week along with 2-3 other rides. Usually averaging 120 miles or so a week and most of the time a full day of rest between rides. I'm also 61 years old and been riding a little over 3 years.