It was a former Disney dude buff arm battle, as "High School Musical" hunk Zac Efron, 25, flashed his tan, ripped muscles before hurting his wrist while filming his new movie in L.A. this week (left) -- while musclebound "Camp Rock" boy bander Joe Jonas, 23, pumped up his God-fearing biceps in a funny new video clip (right).

They've both grown up to be fine young men, so we gotta ask ...

Sorry you creepy weirdos ... Joe Jonas did NOT record a raunchy sex tape with his Swiss model GF ... despite reports to the contrary ... Joe's rep tells TMZ.

Reports have been circulating that Joe -- who once wore a purity ring espousing his virginity -- filmed himself doing the nasty with gf Blanda Eggenschwiler while under the influence of pot and alcohol. The reports claim the sex footage features some crazy BDSM stuff, including paddles and ball gags.

But Joe's rep tells TMZ, it's total BS ... no such tape exists.

The rep says, "There is no truth or validity to the story. It is completely false."

A Jonas Brothers fan has sued the group, claiming they're so popular, she was crushed during a concert by crazed groupies.

Ashleigh Johnson filed the lawsuit -- obtained by TMZ -- in which she claims she was at The Grove in L.A. back in May, 2010, watching the boys perform an early bird special (3 PM), when she was pushed by an uncontrolled crowd against a guard fence.

Ashleigh says she was "agonizingly crushed" into the fence and suffered serious mental, emotional and physical injuries as a result.



Ashleigh -- who didn't ante up her age -- is suing the group as well as Caruso Management, the folks behind The Grove.

Here's a good defense.  Who knew The Jonas Bros. were still popular?

This video ... IS SOOOOOO SAD!!!!

A passionate Jonas Brothers fan waited outside Katsuya in Hollywood last night -- in the cold and the rain -- for a moment with her hero, Kevin Jonas ... only to learn what rejection feels like.

It was SOOOOOO SAD!!!!

FYI -- Kevin DID take pics with a bunch of fans as he left the restaurant with his wife ... trying to please everyone ... but the superfan got lost in the crush and never got a chance to pose with her hero.

Still, SOOOOO SAD!!!!

Joe Jonas checked into an emergency room in L.A. while doctors inspected his abs -- for severe stomach pains -- 48 hours after Joe did some late night partying in Chicago.

A rep for Joe confirms he went to the emergency room at Children's Hospital L.A. on Sunday. We're told Joe was only at the hospital briefly ... and it's not clear what was wrong with him.

One potential hint -- on Friday night (into Saturday morning) Joe was out at a Chicago hot spot Board Room Nightclub (above) partying ... and performed the next night in Chi-Town.

Whatever the problem was ... Joe felt good enough to eat out -- we spotted him and his bro Nick leaving Katsuya last night. Sushi after stomach troubles? Risky, Joe.

Nick Jonas, 18, and his older girlfriend Delta Goodrem, 26, enjoyed an adult unchaperoned vacation in Mexico this weekend.

Hasta la vista purity ring.

Check out some beachin' celebrity doppelgangers -- and vote for which star you think owns the look!

Wearing a vinyl sauna sweat top, newly single Jonas Brother Joe Jonas worked on his fitness in L.A. on Monday.



He's a lean, mean, boy band machine.

Demi Lovato's decision to seek treatment came after she punched a dancer who appeared on "America's Best Dance Crew" ... TMZ has learned.



Sources tell TMZ ... Alex Welch was on the receiving end of Demi's blow.  Welch is a backup dancer on the Jonas Brothers Live in Concert Tour.  She was also a member of Beat Freaks, which got the runner-up title on season 3 of "America's Best Dance Crew."

We're told Welch -- who had a pretty nasty shiner from the incident -- has been talking to lawyers and is considering legal action.

Sources close to Demi say she feels "awful" about her behavior and took personal responsibility for it by leaving the tour and seeking help.

The Jonas Brothers' show must go on ... but it will go on without a replacement for their special guest act Demi Lovato.



A source connected with the tour tells TMZ, "There are no plans to replace Demi for the remaining six days on the Jonas Brothers Live in Concert tour."

As TMZ first reported, Demi decided to leave the tour and seek help for "physical and emotional issues" at a treatment facility.

Disney star Demi Lovato has bailed on an international concert tour with the Jonas Brothers -- and has checked into a treatment center to seek help for "emotional and physical issues" ... TMZ has confirmed through the singer's rep.



In a statement to TMZ, the 18-year-old singer's rep says, "Demi Lovato left her tour early this weekend in order to seek medical treatment for emotional and physical issues she has dealt with for some time."

We're told Demi is not seeking treatment for drug use.

The statement continues, "Demi has decided to take personal responsibility for her actions and seek help.  She is doing just that."

The rep concludes, "[Demi] regrets not being able to finish her tour, but is looking forward to getting back to work in the near future."

Sources close to Lovato tell us the singer was in a physical altercation with a female member of her tour recently ... which was a "catalyst" in her decision to seek professional help.