@Nibor Glad
@DCLane has sorted you. I have just procured a 160mm crankset from Spa Cycles and fitted it with 48t and 38t rings (110 BCD / square taper): after some research it's the best I could do. My daughter wants to see if she can open her hip angle on the TT/tri bike.
I worked out that these (including BB) would be 140g heavier than a 105 5700 setup. They do shorter cranks as well.
Detail (from my message to her):
1) IMO you don't want to spend loadsamoney to try short cranks out, only to find they add little. And you need to go to at least 160, so you can more easily detect an effect. The two potential benefits are: opening your position on the tribars and reducing the work your running specific muscles do so you can run better off the bike.
2) Having looked around, you can give this a go by using these:
https://www.spacycles.co.uk/m2b0s109p2003/SPA-CYCLES-XD-2-Touring-Cranks
with the need to fit a compatible bottom bracket (for square taper suggest UN-55):
https://www.tweekscycles.com/specia...le/shimano-un55-square-tapered-bottom-bracket
3) You will need to fit your own chainrings - these are for 5 bolt chainrings (the image hides the 5th behind the crank arm) (110mm BCD).
4) All up this would cost £40 (plus any expenditure on chainrings, chainring bolts and crank bolts).