I really enjoy weight lifting.  I am just getting into it though.  Do you know much about it?
I sure do, I do strength training to develop the strengthen and increase the size of abdominal muscles
Do you know when weight lifting first became popular?
I'm not too sure since weight training is a pretty specialized excersize that targets certain muscle groups. I assume its been around for as long as people have worked out. 
Are there any downsides you know about for weight lifting?   I do not want to injure myself.
Its all about pacing yourself and not lifting too much at one time, You have to start with the small weights and work up, never start with heavier weights. 
Are there any weight lifting competitions that you know of?
Powerlifting
Powerlifting is a strength sport that consists of three attempts at maximal weight on three lifts: squat, bench press, and deadlift. As in the sport of Olympic weightlifting, it involves the athlete attempting a maximal weight single lift of a barbell loaded with weight plates. Powerlifting evolved from a sport known as "odd lifts", which followed the same three-attempt format but used a wider variety of events, akin to strongman competition. Eventually odd lifts became standardized to the current three.
In competition,
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