I'm not sure what to believe

I'm starting to doubt my GPS. Sure, 4 miles at 12:24 on Monday. I can believe that, even with walking as much as I did. The splits make sense and jibe with how I felt. The splits on today's run just don't make sense. I can't imagine I ran a 7:57, even if it was all downhill.

Turns out the splits are "simulated" from GPS data, and "may be inaccurate." OK, so let's go to the map, which gives a slightly different picture. The map data says I ran that same mile in 10:13. It says I ran the first mile in 11:01. Since when can I run an 11-minute-mile? Since when can I run an almost a 10-minute-mile pace? Even downhill, I've NEVER been that fast! The only thing I think I can really believe in is the overall time, which came in at 11:34. Wait, what?!? 5 miles at a faster pace than I've run anything so far this year?

I'm not sure what to believe.

I know I believe I have absolutely no core strength. I tried to do Chris K's weekly ab/core workout. FAIL! Some of the exercises I couldn't do at all, in part because of my back, but in part because I have no core strength at all. The only ones I could do for a full minute were the toe touches, which are crunches with your legs straight up in the air.

With that workout stinging on my pride, I went out and bought a new toy:

I've had exercise balls in the past, but they didn't survive the way Monkey Boy and my cats played. Monkey Boy is in Germany, and the cats have mellowed and aged a bit. I thought maybe the "anti-burst" feature would help this ball last longer, as well. I'm not sure about the weighted part. My box doesn't talk about keeping my exercise ball in place. It says (in huge yellow letters) "51% more muscle activation than standard exercise balls*." Whatever. As long as it helps me work my core without hurting my back, I'm happy. If I'm running this fast without any core strength at all, imagine what I can do once I'm rocking abs like EMZ!