Is this age related?
Please bear with me while I set the stage for my question. I'm 64, an ex-college football player and have been cycling for a couple decades. After watching my nutrition and riding about 50-75 mi. a week I managed to get my weight down from 197 to 188 lbs. Having lost about an inch in height I'm also down to 5'9" and have a 35 1/2" waist. OK, here's the question. I ride a 15 mi. TT as hard as I can (usually around 17+ mph) and feel great. I also ride 30-35 mi. pretty hard (somewhere in the 16.5 mph range with some significant hills) and also feel good at the end. But, as soon as I do a 30+ mi. ride that has a LOT of hard hills my legs become mush in the last 4-5 mi. (I should mention that I'm pretty slow on the climbs.) My breathing is fine and my heart is strong. But, despite making sure I eat and drink what I'm told I should, I still have leg spasms. Is this just age related and something I should get used to or is there some different approach or training I should try? (Sorry if this is long winded. I'm just at a loss.)