The ability to lift a weight 12 times or more is not optimal for growing muscle mass. If you can't lift a weight eight or more times you are also not optimally building muscle mass. Generally speaking, the target goal for lifting weights to build muscle is anywhere between eight and 12 reps.
You just gotta be more aware
prove to them you can be responsible , or bribe them. both worked for my sister, who is getting two for her birthday next week. just remember when getting them that guinea pigs tend to need a friends so youll need too, and two girls is best
good luck!!!
