Your question is of great interest to me although I am 6 years shy of the desired age you state. Many older riders develop heart timing issues. I have a few timing concerns, so, I went to 4 cardiologists for workups several years ago. They said no limits, do whatever you want. I want to maintain my VO2 max. because it has the highest correlation to mortality and it also is important athletically.
How does one maintain it?
If you read enough studies, I think a reasonable conclusion is some younger athletes respond better to intensity than training volume (hours per year) but everyone responds to volume.
One of my curiosities is why do older riders stop riding? I am a long distance rider, doing stuff like the 1218 km Paris Brest Paris and it is very rare for someone to be able to finish such an event in their 70's and it is 50/50 to complete it at 65 years old. I plan to try it next Summer. But the question of what hits athletes in the 60's?? I think recovery from injuries is a big one. One of the Cardiologists that did my workup was a real sports medicine guy and he said, it isn't your heart that will stop you athletically, it will be orthopedic issues. He casually said be was astounded by my stress test results and I said that I ride a lot (say 15,000 miles per year) and am probably better than average. He then empathatically said, "No, I am absolutely astounded by 18.4 METs, your VO2 Max is 61 or 62".....about what I see with high level HS age cross country runners, not state champs but good runners. My bike numbers like everyone's are very much lower. I have always done a lot of volume whether it is walking or riding a bike.
Leads to the question, how can we measure or track VO2 max.
I have 3 different hills of duration between 3-8 minutes. When ridden as hard as possible, I use the average power on these hills as a proxy for my VO2 max. Unlike my Garmin, hills do not lie.
I had to recover from an accident almost a year ago. I could not ride much but I did 2-3 short intensity efforts per week, say 20-30 minute HIIT. My 5 minute power only dropped from 350 watts to 333 watts over my 5 month recovery. Was that maintenance? Over the last 6 months, I slowly increased my volume to where my CTL is 75-80, which is low for me but it demonstrates how hard it is for an older rider to recover from setbacks and that volume matters. Overtraining is kind of a setback. Too many intervals can cause overtraining or certainly excessive overreaching. In terms of intervals, I do either Ronnestad intervals or the classic, brutally difficult 4 x 5 minutes at 112-120% of FTP. I never do intervals more often than once every 10 days. I only do them when I feel really good and feeling like I can set a
PR up my hills. I recently hit a personal best power for 5 minutes. I ride 14-18 hours per week on terrain with 50-60 feet/mile of elevation and I keep my pace on climbs to Tempo at the most and try to keep all of my riding to Z2. Is there a better approach for me? I don't know. But I do not do intervals easy, they are balls to the wall. My Cardologist says it is fine.
I don't think there are any controlled studies for 70+ athletes out there but please take this youngins N = 1 experience with a grain of salt. Look up Dill and his lifelong measurements at Harvard. He was a big hiker and endurance enthusiast in general. Pollock's study is classic.
At the fairly inactive end of Rogers’ athletic group, the losses in VO2max were greater. Two athletes who cut training volume by 30% or more experienced VO2max losses of about 1% per year. By contrast, a 55-year-old, national-class athlete, who completely maintained the quantity and quality of his training, preserved all of his VO2max – and actually improved his competitive performances – over the entire study period! Such perfect preservation of aerobic capacity by very hard-working veterans was, of course, the same finding made by Pollock in his 10-year study.
Pollock pointed out that one of the most difficult problems faced by veteran athletes is simply the near impossibility of sustaining very high-quality training over a period as long as ten years, especially when the body is beginning to show signs of ‘wear and tear'(6). It is not that veterans can no longer plan and carry out very rugged training sessions; rather that the physiological recovery processes may slow with age, thus increasing the risk of injury and lowering the actual frequency of torrid, fitness-maximising workouts.
That is my experience, too. (emphasis added). Don't get injured and be careful with intensity because recovery is lessened. If Coggan hadn't been thrown off all forums around the world, you could ask him, he is like 90 years old or something. His relatively low decline in VO2 max is pretty astounding.
https://www.sportsperformancebulleti...obic-capacity/
https://www.trainingpeaks.com/blog/z...ance-athletes/