Rihanna is one of the busiest women in music, and it's starting to show. The starlet, who is gearing up for a new album and tour, delivered what many of her fans (make that her "Navy") considered a performance that was less than stellar at the iHeart Radio Festival.

The 'Battleship' starlet's live shows are known more for their amazing sets, choreography and outfits than for Rihanna's actual vocal performance, but even the dancing in her set seemed somewhat half-hearted.

In 'Where Have You Been,' the songbird's vocals sounded especially strained, even silenced at certain points. Her use of a backing track is understandable given her always-intricate choreography, but she barely even sings along to it even when she's merely sitting on a golden throne. Flanked by tribal-style dancers similar to the ones in her video, she actually appears a bit sleepy, though she still looks stunning in her metallic silver basketball jersey, deep plum lipstick, wine-colored nails, short black boots and matching hat.

RiRi did deliver a few surprises, including a performance of 'Live Your Life,' great instrumental arrangements for 'What's My Name' and some audience interaction during 'Umbrella' that was pretty amusing to watch.

It's a sharp contrast to the singer's recent live sets with Coldplay, in which she performed 'Princess of China' and 'We Found Love' beautifully. Perhaps the singer is just exhausted -- with a schedule like hers, we could totally understand that. Someone book this girl for a nap so she can show everyone what she's really made of!

Watch Rihanna Perform 'Live Your Life' at the iHeart Radio Music Festival

Watch Rihanna Perform 'S&M' at the iHeart Radio Musical Festival

Watch Rihanna Perform 'Umbrella' at the iHeart Radio Music Festival

Watch Rihanna Perform 'Please Don't Stop the Music' at the iHeart Radio Music Festival

Watch Rihanna Perform 'What's My Name' at the iHeart Radio Music Festival

Watch Rihanna Perform 'Only Girl in the World' at the iHeart Radio Music Festival

Watch Rihanna Perform 'Disturbia' at the iHeart Radio Music Festival