It primarily trains JR but does improve JS too (and not at a bad rate either). I think these may be a bit different now but for a 6'0 18 year old (with a superior trainer) you get 0.21 JS, 0.62 JR, 0.07 DR and 0.08 HA per week of training.
Last edited by js8 at 7/1/2015 5:21:42 PM