Discussion: How far can I push my body?

I see older people doing some incredible things. Mostly it motivates and inspires me but I do feel jealousy too. It got too cold to keep doing speed but I also thought about what I had been doing...adding 440's and even 880 and I am thinking they were too slow to benefit me fully...they were still far faster than if I jogged along but I have to battle my form and I get more benefit of 'smoothing out' my form from the 100 meter surges.

They even hurt enough that more than a mile of it is tough for me mentally...BUT my form feels ragged again so I think I need to go back to doing more of the trot/stride 100 meter alterations. I need leg turn over...I'm not sure of the pace of the 'surges' but the pace is not nearly as fast as they 'feel'...probably 6:30 to even as slow as 7 min pace on the slower ones.

When I first started these a few years ago I think I was going 6 min pace on the faster one...the time per mile is about the same but I'm 'cheating' on these by doing 110 to 115 yards/meters on the stride part...blah blah blah...I did three 7.5 mile runs in less than two weeks and I've been wiped out since I finished Thursday.

The sore hip had pretty well gone away now it's like my knee...it's controllable and manageable but I have to 'work' at it...oddly enough it does not bother me running so for now it's 'good'...or 'okay'.

At the same time I do not know that my body could hold up to the training required to finish a marathon under 4 hours. I can see trotting and even walking and doing 12 minute pace for a marathon but not sure I want to do that. (You mentioned Dave Wicker ran slowly but he's probably doing 10 minute pace and unfortunately that is a quick training pace for me right now).