Hmm. Walking is (AGI * 2)m/turn; running is up to (AGI * 4)m/turn. Sprinting adds 1m/turn per hit for a complex action. Stand back - I'm going to use SCIENCE!!
Usain Bolt, the world's current fastest man and record-holder, made 100m in 9.572s. He averaged 31.3m/turn. Divided by 4, this would put his agility at a 7.8: clearly not something a human (by Shadowrun rules) is capable of. At best, he would have a 7; let's give him a 6. That gives him 24 out of those 31-and-a-third meters; we have to pick up 7.3414m per turn, or 22m across three combat turns, from somewhere.
Let's also presume that as an ordinary human, for those adrenaline-charged three-and-a-bit combat turns he gets 2 actions per comat turn - and that he spends each of those Turns Sprinting. (You know, being a sprinter, and all, huh?) So between those six combat phases, he has to get an average of 3.67 hits on his Running roll. Hey, easy - he's already got a 6 in Agility, so ... oh wait - Running is based off Strength. Not so easy any more. Still, he's a pro - he's THE Pro From Jamaica, after all, so how many dice is he looking at ? 11 is going to get him the average he needs. If he has an Agility under 6, though, he needs that skill pool to be six dice higher for every point of Agility lower. Which means he might be a 5 STR 5 AGI character with a skill of 12.
So in order to equal the current fastest-man-in-the-world, a guy who's sprinting at 37.61 kph, you need an AGI of 6 plus a Running/Sprint skill pool of 11 - i.e. a STR of 5 and a skill of 6, or skill of 4 with +2 for Sprinting. This does not look to me to be 'way crazy'; this looks, y'know, pretty near spot-on.
The thing with higher attribute levels is that they require modifications to your body, whether magical or technological, that are incredibly insane by normal standards. From what I recall of the National Geographic article, scientists today believe that the top speed a human being's body could possibly ever achieve would be about 40 mph, just under 65 kph, due to the limits of muscle, bone, and sinew. I have a character who is specifically designed to hit that target - and she does, pushing the edge somewhat. This is a character with Exceptional Attribute and - looking ahead - Metagenetic Improvement, both applied to her Agility. She has enhancements that lift her Agility to a mind-blowing 13. And you know what? With all that, her Running speed hits just under 40mph, with her sprint speed (Natural Athlete, Strength 8 w/ enhancements, but Running only at a 3, so an average 4 successes) hitting 44.75m/turn if she spends only one action on it. Is this fast? Oh, hell yes. She's incredibly fast coming out of the gate, that physical rapidity has been a hallmark of the character since day one, and she's managed some serious spotlight moments because the GM thought the guy with a machine was far enough away at 13m to be able to shoot me before I got to him. (Not true. Poor bastard.)
What one has to remember is that anyone who does these things is someone whose entire body has been infused with better-than-metahuman tech and/or magic in order to do them. They should be able to sprint at 72 kph, kicking Mssr. Bolt's measly 37.6kph ass all around the track; they're built for it, reinforced for it. You want something sad, though? A maxed-out Troll (BOD/STR of 15 each) cannot deadlift the current world-record by a baseline human of 460kg. There's something that needs adjusting ...
In regards to the spirit-enhancement, though, the idea is that the spirit guides you and protects you as well as increases your speed - which means turning and stopping should be no problem. A GM who plays differently is, IMO, screwing with his players, and they should take every chance to turn that ruling around so that spirits drive NPCs into walls at high speeds. I also have experience of the supermach vehicle (an ultralite in our campaign); we houseruled that the fastest a vehicle could go was the spirit's Fast Astral Movement Rate, i.e. Force * 1000 kph. If the current SR5 rule for spirits and Movement is 'increases its Movement attribute by hits', I intend to houserule it back down to the hits being a raw multiplier.
