I am using 5lbs weights to start...don't think it'll become too easy for me (I'm weak) lol...I'd say until it isn't challenging you, then use the weights that fatigue your muscles after the first 12-15 reps.

I'm feeling extremely weak reading this. I've been using 2's and 4's. Generally, use 4s the first time through the circuit and 2s the second time. I also found that last circuit in week one too hard to ever get to the 4s - In addition to the challenge of the exercises themselves, I think the muscles are just fatigued by this point.

Did workout 1 of week 2 on Saturday and only used the 2s - until I could assess how I did. Found the workout very challenging and actually set down the weights entirely for the last set.

I figure, once I get through 4 weeks, I can start over with 6s & 4s and it'll be a whole new challenge

5, 8 and 10 lb. I use a 35 lb sandbag for the deadlift rows and a 15 lb kettlebell for the squat-swings (I'm just doing week 1 currently).

On the front shoulder raise even the 5s make me miserable on the second round. Yowza!