To be clear, given the same knowledge, opportunity, motivation, coaching and finances, my younger self would trounce my older self. Running and throwing, there is no comparison between my 20s and 70s. I suck at both today. Vertical jumping, I am about the same which is odd but I will take it. I am better today cycling in climbing and time trialing today but that is because I did not train properly in my 20s and did not have the motivation. Today, I train and cycle with the best athletes in my age group. That is a big factor. Great competition and belief in oneself.
And not to turn this into a Pills and Ills thread but injuries and joint degradation play a monster role for me in loss of athletic capability. I have a terrible back. The MRI and X-rays will scare the bejesus out of anyone. On a positive note, I have an excellent spine specialty doc at UCSD medical who recommended and wrote a prescription for a PT group that specializes in pro athletes versus a traditional hospital PT setting. They have helped me a lot with my mobility. It has taken months but my spine and hip mobility as measured objectively by them have improved dramatically. The pathology is unchanged.
The mobility exercises are very hard to do starting out. Sometimes, I could not do them at all and sometimes they caused a lot of pain. It was like, dude, you have to be kidding, old guys cannot do this. However, it was all about small movements or attempts to fire muscles to make a small movement. Over time, the movement improved. Also, being in a PT setting with highly motivated athletes and therapists is better than a hospital setting with typical patients in for rehab. So today, I do a strength workout and mobility workout in the gym and the mobility takes longer than the strength. I have a specific mobility warmup and cool down routine for cycling.
I have found I am much stronger in the gym and on the bike with increased hip and spine mobility. YMMV.