I have always included light dumbells in my daily cardio workout sessions at home. I think exercise alone will not give you the full benefits like combining it with light weights would. Weight lifting helps in increasing the strength and force of the exercise regime which therefore provides faster and better impact and results. However, you need to always bear in mind to use only weights that suit your size and weight, else you might risk suffering from sprains and other muscular injuries.
Weight lifting has never came across my mind as a workout regime. I have always looked at it as a more advanced toning regime that is unnecessary unless you wish to take part in a body building competition. Light weight lifting is still acceptable for those who have excess skin and flab issues thus weight lifting is ideal for them. I think it is best to consult a professional trainer else much more than just muscle spasms could occur to you.